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Demas GE, Munley KM, Jasnow AM. A seasonal switch hypothesis for the neuroendocrine control of aggression. Trends Endocrinol Metab 2023; 34:799-812. [PMID: 37722999 DOI: 10.1016/j.tem.2023.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/22/2023] [Accepted: 08/23/2023] [Indexed: 09/20/2023]
Abstract
Aggression is a well-studied social behavior that is universally exhibited by animals across a wide range of contexts. Prevailing knowledge suggests gonadal steroids primarily mediate aggression; however, this is based mainly on studies of male-male aggression in laboratory rodents. When males and females of other species, including humans, are examined, a positive relationship between gonadal steroids and aggression is less substantiated. For instance, hamsters housed in short 'winter-like' days show increased aggression compared with long-day housed hamsters, despite relatively low circulating gonadal steroids. These results suggest alternative, non-gonadal mechanisms controlling aggression. Here, we propose the seasonal switch hypothesis, which employs a multidisciplinary approach to describe how seasonal variation in extra-gonadal steroids, orchestrated by melatonin, drives context-specific changes in aggression.
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Affiliation(s)
- Gregory E Demas
- Department of Biology, Program in Neuroscience, and Program in Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Kathleen M Munley
- Department of Psychology, University of Houston, Houston, TX 77204, USA
| | - Aaron M Jasnow
- Department of Pharmacology, Physiology & Neuroscience, University of South Carolina School of Medicine, Columbia, SC 29209, USA
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2
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Munley KM, Sinkiewicz DM, Szwed SM, Demas GE. Sex and seasonal differences in neural steroid sensitivity predict territorial aggression in Siberian hamsters. Horm Behav 2023; 154:105390. [PMID: 37354601 PMCID: PMC10527453 DOI: 10.1016/j.yhbeh.2023.105390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 05/01/2023] [Accepted: 05/28/2023] [Indexed: 06/26/2023]
Abstract
Many animals display marked changes in physiology and behavior on a seasonal timescale, including non-reproductive social behaviors (e.g., aggression). Previous studies from our lab suggest that the pineal hormone melatonin acts via steroid hormones to regulate seasonal aggression in Siberian hamsters (Phodopus sungorus), a species in which both males and females display increased non-breeding aggression. The neural actions of melatonin on steroids and aggressive behavior, however, are relatively unexplored. Here, we housed male and female hamsters in long-day photoperiods (LDs, characteristic of breeding season) or short-day photoperiods (SDs, characteristic of non-breeding season) and administered timed melatonin (M) or control injections. Following 10 weeks of treatment, we quantified aggressive behavior and neural steroid sensitivity by measuring the relative mRNA expression of two steroidogenic enzymes (aromatase and 5α-reductase 3) and estrogen receptor 1 in brain regions associated with aggression or reproduction [medial preoptic area (MPOA), anterior hypothalamus (AH), arcuate nucleus (ARC), and periaqueductal gray (PAG)] via quantitative PCR. Although LD-M and SD males and females displayed increased aggression and similar changes in gene expression in the ARC, there were sex-specific effects of treatment with melatonin and SDs on gene expression in the MPOA, AH, and PAG. Furthermore, males and females exhibited different relationships between neural gene expression and aggression in response to melatonin and SDs. Collectively, these findings support a role for melatonin in regulating seasonal variation in neural steroid sensitivity and aggression and reveal how distinct neuroendocrine responses may modulate a similar behavioral phenotype in male and female hamsters.
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Affiliation(s)
- Kathleen M Munley
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Department of Psychology, University of Houston, Houston, TX 77204, USA.
| | - David M Sinkiewicz
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Sydney M Szwed
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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3
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French SS, Demas GE, Lopes PC. From mechanism to ecosystem: building bridges between ecoimmunology, psychoneuroimmunology and disease ecology. J Exp Biol 2023; 226:jeb245858. [PMID: 37458064 DOI: 10.1242/jeb.245858] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
Historically, the fields of ecoimmunology, psychoneuroimmunology and disease ecology have taken complementary yet disparate theoretical and experimental approaches, despite sharing critical common themes. Researchers in these areas have largely worked independently of one another to understand mechanistic immunological responses, organismal level immune performance, behavioral changes, and host and parasite/disease population dynamics, with few bridges across disciplines. Although efforts to strengthen and expand these bridges have been called for (and occasionally heeded) over the last decade, more integrative studies are only now beginning to emerge, with critical gaps remaining. Here, we briefly discuss the origins of these key fields, and their current state of integration, while highlighting several critical directions that we suggest will strengthen their connections into the future. Specifically, we highlight three key research areas that provide collaborative opportunities for integrative investigation across multiple levels of biological organization, from mechanisms to ecosystems: (1) parental effects of immunity, (2) microbiome and immune function and (3) sickness behaviors. By building new bridges among these fields, and strengthening existing ones, a truly integrative approach to understanding the role of host immunity on individual and community fitness is within our grasp.
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Affiliation(s)
- Susannah S French
- Department of Biology and the Ecology Center, Utah State University, Logan, UT 84322, USA
| | - Gregory E Demas
- Department of Biology and Program in Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Patricia C Lopes
- Schmid College of Science and Technology, Chapman University, Orange, CA 92866, USA
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4
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Munley KM, Han Y, Lansing MX, Demas GE. Winter madness: Melatonin as a neuroendocrine regulator of seasonal aggression. J Exp Zool A Ecol Integr Physiol 2022; 337:873-889. [PMID: 35451566 PMCID: PMC9587138 DOI: 10.1002/jez.2601] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/16/2022] [Accepted: 04/07/2022] [Indexed: 12/25/2022]
Abstract
Individuals of virtually all vertebrate species are exposed to annual fluctuations in the deterioration and renewal of their environments. As such, organisms have evolved to restrict energetically expensive processes and activities to a specific time of the year. Thus, the precise timing of physiology and behavior is critical for individual reproductive success and subsequent fitness. Although the majority of research on seasonality has focused on seasonal reproduction, pronounced fluctuations in other non-reproductive social behaviors, including agonistic behaviors (e.g., aggression), also occur. To date, most studies that have investigated the neuroendocrine mechanisms underlying seasonal aggression have focused on the role of photoperiod (i.e., day length); prior findings have demonstrated that some seasonally breeding species housed in short "winter-like" photoperiods display increased aggression compared with those housed in long "summer-like" photoperiods, despite inhibited reproduction and low gonadal steroid levels. While fewer studies have examined how the hormonal correlates of environmental cues regulate seasonal aggression, our previous work suggests that the pineal hormone melatonin acts to increase non-breeding aggression in Siberian hamsters (Phodopus sungorus) by altering steroid hormone secretion. This review addresses the physiological and cellular mechanisms underlying seasonal plasticity in aggressive and non-aggressive social behaviors, including a key role for melatonin in facilitating a "neuroendocrine switch" to alternative physiological mechanisms of aggression across the annual cycle. Collectively, these studies highlight novel and important mechanisms by which melatonin regulates aggressive behavior in vertebrates and provide a more comprehensive understanding of the neuroendocrine bases of seasonal social behaviors broadly.
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Affiliation(s)
- Kathleen M. Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Yuqi Han
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Matt X. Lansing
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E. Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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Munley KM, Trinidad JC, Demas GE. Sex-specific endocrine regulation of seasonal aggression in Siberian hamsters. Proc Biol Sci 2022; 289:20220668. [PMID: 36100021 PMCID: PMC9470250 DOI: 10.1098/rspb.2022.0668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 08/23/2022] [Indexed: 11/12/2022] Open
Abstract
Coordinating physiological and behavioural processes across the annual cycle is essential in enabling individuals to maximize fitness. While the mechanisms underlying seasonal reproduction and its associated behaviours are well characterized, fewer studies have examined the hormonal basis of non-reproductive social behaviours (e.g. aggression) on a seasonal time scale. Our previous work suggests that the pineal hormone melatonin facilitates a 'seasonal switch' in neuroendocrine regulation of aggression in male and female Siberian hamsters (Phodopus sungorus), specifically by acting on the adrenal glands to increase the production of the androgen dehydroepiandrosterone (DHEA) during the short-day (SD) photoperiods of the non-breeding season. Here, we provide evidence that the activity of 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD), a key enzyme within the steroidogenic pathway that mediates DHEA synthesis and metabolism, varies in a sex-specific and melatonin-dependent manner. Although both male and female hamsters displayed increased aggression in response to SDs and SD-like melatonin, only males showed an increase in adrenal 3β-HSD activity. Conversely, SD and melatonin-treated females exhibited reductions in both adrenal and neural 3β-HSD activity. Collectively, these results suggest a potential role for 3β-HSD in modulating non-breeding aggression and, more broadly, demonstrate how distinct neuroendocrine mechanisms may underlie the same behavioural phenotype in males and females.
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Affiliation(s)
- Kathleen M. Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
| | - Jonathan C. Trinidad
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN 47405, USA
| | - Gregory E. Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, 1001 East Third Street, Bloomington, IN 47405, USA
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Harshaw C, Kojima S, Wellman CL, Demas GE, Morrow AL, Taft DH, Kenkel WM, Leffel JK, Alberts JR. Maternal antibiotics disrupt microbiome, behavior, and temperature regulation in unexposed infant mice. Dev Psychobiol 2022; 64:e22289. [PMID: 35748626 PMCID: PMC9236156 DOI: 10.1002/dev.22289] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 04/21/2022] [Accepted: 05/12/2022] [Indexed: 12/31/2022]
Abstract
Maternal antibiotic (ABx) exposure can significantly perturb the transfer of microbiota from mother to offspring, resulting in dysbiosis of potential relevance to neurodevelopmental disorders such as autism spectrum disorder (ASD). Studies in rodent models have found long-term neurobehavioral effects in offspring of ABx-treated dams, but ASD-relevant behavior during the early preweaning period has thus far been neglected. Here, we exposed C57BL/6J mouse dams to ABx (5 mg/ml neomycin, 1.25 μg/ml pimaricin, .075% v/v acetic acid) dissolved in drinking water from gestational day 12 through offspring postnatal day 14. A number of ASD-relevant behaviors were assayed in offspring, including ultrasonic vocalization (USV) production during maternal separation, group huddling in response to cold challenge, and olfactory-guided home orientation. In addition, we obtained measures of thermoregulatory competence in pups during and following behavioral testing. We found a number of behavioral differences in offspring of ABx-treated dams (e.g., modulation of USVs by pup weight, activity while huddling) and provide evidence that some of these behavioral effects can be related to thermoregulatory deficiencies, particularly at younger ages. Our results suggest not only that ABx can disrupt microbiomes, thermoregulation, and behavior, but that metabolic effects may confound the interpretation of behavioral differences observed after early-life ABx exposure.
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Affiliation(s)
| | - Sayuri Kojima
- Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN
| | - Cara L. Wellman
- Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN
| | | | - Ardythe L. Morrow
- Department of Environmental Health, University of Cincinnati College of Medicine, Cincinnati, OH
| | - Diana Hazard Taft
- Department of Food Science and Technology, University of California, Davis, Davis, CA
| | - William M. Kenkel
- Department of Psychological and Brain Sciences, University of Delaware, Newark, DE
| | - Joseph K. Leffel
- Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN
| | - Jeffrey R. Alberts
- Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN
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7
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Cusick JA, Wellman CL, Demas GE. Maternal stress and the maternal microbiome have sex-specific effects on offspring development and aggressive behavior in Siberian hamsters (Phodopus sungorus). Horm Behav 2022; 141:105146. [PMID: 35276524 DOI: 10.1016/j.yhbeh.2022.105146] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 02/18/2022] [Accepted: 02/21/2022] [Indexed: 11/29/2022]
Abstract
The gut microbiome, a community of commensal, symbiotic and pathogenic bacteria, fungi, and viruses, interacts with many physiological systems to affect behavior. Prenatal experiences, including exposure to maternal stress and different maternal microbiomes, are important sources of organismal variation that can affect offspring development. These physiological systems do not act in isolation and can have long-term effects on offspring development and behavior. Here we investigated the interactive effects of maternal stress and manipulations of the maternal microbiome on offspring development and social behavior using Siberian hamsters, Phodopus sungorus. We exposed pregnant females to either a social stressor, antibiotics, both the social stressor and antibiotics, or no treatment (i.e., control) over the duration of their pregnancy and quantified male and female offspring growth, gut microbiome composition and diversity, stress-induced cortisol concentrations, and social behavior. Maternal antibiotic exposure altered the gut microbial communities of male and female offspring. Maternal treatment also had sex-specific effects on aspects of offspring development and aggressive behavior. Female offspring produced by stressed mothers were more aggressive than other female offspring. Female, but not male, offspring produced by mothers exposed to the combined treatment displayed low levels of aggression, suggesting that alteration of the maternal microbiome attenuated the effects of prenatal stress in a sex-specific manner. Maternal treatment did not affect non-aggressive behavior in offspring. Collectively, our study offers insight into how maternal systems can interact to affect offspring in sex-specific ways and highlights the important role of the maternal microbiome in mediating offspring development and behavior.
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Affiliation(s)
- Jessica A Cusick
- Department of Biology, Utah Valley University, United States of America; Department of Biology, Indiana University, United States of America; Animal Behavior Program, Indiana University, United States of America.
| | - Cara L Wellman
- Animal Behavior Program, Indiana University, United States of America; Department of Psychological and Brain Sciences, Indiana University, United States of America; Program in Neuroscience, Indiana University, United States of America
| | - Gregory E Demas
- Department of Biology, Indiana University, United States of America; Animal Behavior Program, Indiana University, United States of America; Program in Neuroscience, Indiana University, United States of America
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8
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Munley KM, Dutta S, Jasnow AM, Demas GE. Adrenal MT 1 melatonin receptor expression is linked with seasonal variation in social behavior in male Siberian hamsters. Horm Behav 2022; 138:105099. [PMID: 34920297 PMCID: PMC8847318 DOI: 10.1016/j.yhbeh.2021.105099] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 11/10/2021] [Accepted: 11/24/2021] [Indexed: 02/03/2023]
Abstract
Many animals exhibit pronounced changes in physiology and behavior on a seasonal basis, and these adaptations have evolved to promote survival and reproductive success. While the neuroendocrine pathways mediating seasonal reproduction are well-studied, far less is known about the mechanisms underlying seasonal changes in social behavior, particularly outside of the context of the breeding season. Our previous work suggests that seasonal changes in melatonin secretion are important in regulating aggression in Siberian hamsters (Phodopus sungorus); it is unclear, however, how melatonin acts via its receptors to modulate seasonal variation in social behavior. In this study, we infused a MT1 melatonin receptor-expressing (MT1) or control (CON) lentivirus into the adrenal glands of male Siberian hamsters. We then housed hamsters in long-day (LD) or short-day (SD) photoperiods, administered timed melatonin or control injections, and quantified aggressive and non-aggressive social behaviors (e.g., investigation, self-grooming) following 10 weeks of treatment. LD hamsters infused with the MT1 lentivirus had significantly higher adrenal mt1 expression than LD CON hamsters, as determined via quantitative PCR. While melatonin administration was necessary to induce SD-like reductions in body and relative reproductive mass, only LD hamsters infused with the MT1 lentivirus displayed SD-like changes in social behavior, including increased aggression and decreased investigation and grooming. In addition, SD CON and LD hamsters infused with the MT1 lentivirus exhibited similar relationships between adrenal mt1 expression and aggressive behavior. Together, our findings suggest a role for adrenal MT1 receptor signaling in regulating behavior, but not energetics or reproduction in seasonally breeding species.
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Affiliation(s)
- Kathleen M Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Sohini Dutta
- Department of Psychological Sciences, Kent State University, Kent, OH 44240, USA; Department of Neuroscience, Mount Sinai School of Medicine, New York, NY 10029, USA
| | - Aaron M Jasnow
- Department of Psychological Sciences, Kent State University, Kent, OH 44240, USA; Department of Pharmacology, Physiology & Neuroscience, University of South Carolina School of Medicine, Columbia, SC 29209, USA
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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9
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Bailey AM, Hall CA, Legan SJ, Demas GE. Food restriction during development delays puberty but does not affect adult seasonal reproductive responses to food availability in Siberian hamsters (Phodopus sungorus). J Exp Zool A Ecol Integr Physiol 2021; 335:691-702. [PMID: 34343418 DOI: 10.1002/jez.2534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/19/2021] [Accepted: 07/20/2021] [Indexed: 11/08/2022]
Abstract
Seasonally breeding animals respond to environmental cues to determine optimal conditions for reproduction. Siberian hamsters (Phodopus sungorus) primarily rely on photoperiod as a predictive cue of future energy availability. When raised in long-day photoperiods (>14 h light), supplemental cues such as food availability typically do not trigger the seasonal reproductive response of gonadal regression, which curtails reproduction in unsuitable environments. We investigated whether recognition of food availability as a cue could be altered by a nutritional challenge during development. Specifically, we predicted that hamsters receiving restricted food during development would be sensitized to food restriction (FR) as adults and undergo gonadal regression in response. Male and female hamsters were given either ad libitum (AL) food or FR from weaning until d60. The FR treatment predictably limited growth and delayed puberty in both sexes. For 5 weeks after d60, all hamsters received an AL diet to allow FR hamsters to gain mass equal to AL hamsters. Then, adult hamsters of both juvenile groups received either AL or FR for 6 weeks. Juvenile FR had lasting impacts on adult male body mass and food intake. Adult FR females exhibited decreased estrous cycling and uterine horn mass indiscriminately of juvenile food treatment, but there was little effect on male reproductive measurements. Overall, we observed a delay in puberty in response to postweaning FR, but this delay appeared not to affect seasonal reproductive responses in the long term. These findings increase our understanding of seasonal reproductive responses in a relevant environmental context.
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Affiliation(s)
- Allison M Bailey
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Carlisha A Hall
- Department of Biology, University of North Carolina, Pembroke, North Carolina, USA
| | - Sandra J Legan
- Department of Physiology, University of Kentucky, Lexington, Kentucky, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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10
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Adaniya CH, Wellman CL, Demas GE, Cusick JA. The ontogeny of personality: Repeatability of social and escape behaviors across developmental stages in Siberian hamsters (Phodopus sungorus). J Exp Zool A Ecol Integr Physiol 2021; 335. [PMID: 34184832 DOI: 10.1002/jez.2499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 06/16/2021] [Indexed: 01/09/2023]
Abstract
Animal personality is defined as behavioral tendencies that are consistent across time and contexts within an individual, but differ across individuals. Studies investigating personality typically examine individuals across short time periods or within a single life stage. Growing evidence suggests that personality may be less stable across life stages, highlighting the need to consider the effects of ontogeny on the expression of consistent behavioral traits. We investigated individual consistency in social and escape behaviors across developmental stages using Siberian hamsters (Phodopus sungorus). To determine whether individuals were consistent in these behaviors as juveniles and across developmental stages, we measured male and female social and escape behaviors twice as juveniles and once as adults. Individuals' social scores were significantly repeatable within the juvenile stage, but not across developmental stages. In contrast, escape scores were highly repeatable across developmental stages, with males' scores being more repeatable than females' scores. Our results support previous findings that personality traits, especially those associated with social behavior, are less stable across development, whereas behaviors associated with stress or coping may represent a more permanent feature of an individual's phenotype. Our results also indicate potential sex differences in long-term repeatability of personality. Considering how ontogeny affects animal personality for males and females can provide insight into the evolution and mechanisms that maintain animal personality.
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Affiliation(s)
| | - Cara L Wellman
- Animal Behavior Program, Indiana University, Bloomington, Indiana, USA.,Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, Indiana, USA.,Animal Behavior Program, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Jessica A Cusick
- Department of Biology, Indiana University, Bloomington, Indiana, USA.,Animal Behavior Program, Indiana University, Bloomington, Indiana, USA
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Abstract
On and within most sites across an animal's body live complex communities of microorganisms. These microorganisms perform a variety of important functions for their hosts, including communicating with the brain, immune system and endocrine axes to mediate physiological processes and affect individual behaviour. Microbiome research has primarily focused on the functions of the microbiome within the gastrointestinal tract (gut microbiome) using biomedically relevant laboratory species (i.e. model organisms). These studies have identified important connections between the gut microbiome and host immune, neuroendocrine and nervous systems, as well as how these connections, in turn, influence host behaviour and health. Recently, the field has expanded beyond traditional model systems as it has become apparent that the microbiome can drive differences in behaviour and diet, play a fundamental role in host fitness and influence community-scale dynamics in wild populations. In this Review, we highlight the value of conducting hypothesis-driven research in non-model organisms and the benefits of a comparative approach that assesses patterns across different species or taxa. Using social behaviour as an intellectual framework, we review the bidirectional relationship between the gut microbiome and host behaviour, and identify understudied mechanisms by which these effects may be mediated.
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Affiliation(s)
- Jessica A. Cusick
- Department of Biology, Indiana University, Biology Building 142, 1001 East Third Street, Bloomington, IN 47405, USA
- Animal Behavior Program, Indiana University, 409 N. Park Avenue, Bloomington, IN 47405, USA
| | - Cara L. Wellman
- Animal Behavior Program, Indiana University, 409 N. Park Avenue, Bloomington, IN 47405, USA
- Department of Psychological and Brain Sciences, Indiana University, 1101 E. 10th Street, Bloomington, IN 47405-7007, USA
- Program in Neuroscience, Indiana University, Psychology Building, 1101 E 10th Street Bloomington, IN 47405-2204, USA
| | - Gregory E. Demas
- Department of Biology, Indiana University, Biology Building 142, 1001 East Third Street, Bloomington, IN 47405, USA
- Animal Behavior Program, Indiana University, 409 N. Park Avenue, Bloomington, IN 47405, USA
- Program in Neuroscience, Indiana University, Psychology Building, 1101 E 10th Street Bloomington, IN 47405-2204, USA
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12
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Munley KM, Trinidad JC, Deyoe JE, Adaniya CH, Nowakowski AM, Ren CC, Murphy GV, Reinhart JM, Demas GE. Melatonin-dependent changes in neurosteroids are associated with increased aggression in a seasonally breeding rodent. J Neuroendocrinol 2021; 33:e12940. [PMID: 33615607 DOI: 10.1111/jne.12940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/15/2020] [Accepted: 01/11/2021] [Indexed: 02/06/2023]
Abstract
Aggression is a complex social behaviour that allows individuals to compete for access to limited resources (eg, mates, food and territories). Excessive or inappropriate aggression, however, has become problematic in modern societies, and current treatments are largely ineffective. Although previous work in mammals suggests that aggressive behaviour varies seasonally, seasonality is largely overlooked when developing clinical treatments for inappropriate aggression. Here, we investigated how the hormone melatonin regulates seasonal changes in neurosteroid levels and aggressive behaviour in Siberian hamsters, a rodent model of seasonal aggression. Specifically, we housed males in long-day (LD) or short-day (SD) photoperiods, administered timed s.c. melatonin injections (which mimic a SD-like signal) or control injections, and measured aggression using a resident-intruder paradigm after 9 weeks of treatment. Moreover, we quantified five steroid hormones in circulation and in brain regions associated with aggressive behaviour (lateral septum, anterior hypothalamus, medial amygdala and periaqueductal gray) using liquid chromatography-tandem mass spectrometry. SD hamsters and LD hamsters administered timed melatonin injections (LD-M) displayed increased aggression and exhibited region-specific decreases in neural dehydroepiandrosterone, testosterone and oestradiol, but showed no changes in progesterone or cortisol. Male hamsters also showed distinct associations between neurosteroids and aggressive behaviour, in which neural progesterone and dehydroepiandrosterone were positively correlated with aggression in all treatment groups, whereas neural testosterone, oestradiol and cortisol were negatively correlated with aggression only in LD-M and SD hamsters. Collectively, these results provide insight into a novel neuroendocrine mechanism of mammalian aggression, in which melatonin reduces neurosteroid levels and elevates aggressive behaviour.
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Affiliation(s)
- Kathleen M Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | | | - Jessica E Deyoe
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Catherine H Adaniya
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Andrea M Nowakowski
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Clarissa C Ren
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Grace V Murphy
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - John M Reinhart
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
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13
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Rendon NM, Petersen CL, Munley KM, Amez AC, Boyes DL, Kingsbury MA, Demas GE. Seasonal patterns of melatonin alter aggressive phenotypes of female Siberian hamsters. J Neuroendocrinol 2020; 32:e12894. [PMID: 32808694 DOI: 10.1111/jne.12894] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/19/2020] [Accepted: 07/15/2020] [Indexed: 12/16/2022]
Abstract
Many animal species exhibit year-round aggression, a behaviour that allows individuals to compete for limited resources in their environment (eg, food and mates). Interestingly, this high degree of territoriality persists during the non-breeding season, despite low levels of circulating gonadal steroids (ie, testosterone [T] and oestradiol [E2 ]). Our previous work suggests that the pineal hormone melatonin mediates a 'seasonal switch' from gonadal to adrenal regulation of aggression in Siberian hamsters (Phodopus sungorus); solitary, seasonally breeding mammals that display increased aggression during the short, 'winter-like' days (SDs) of the non-breeding season. To test the hypothesis that melatonin elevates non-breeding aggression by increasing circulating and neural steroid metabolism, we housed female hamsters in long days (LDs) or SDs, administered them timed or mis-timed melatonin injections (mimic or do not mimic a SD-like signal, respectively), and measured aggression, circulating hormone profiles and aromatase (ARO) immunoreactivity in brain regions associated with aggressive or reproductive behaviours (paraventricular hypothalamic nucleus [PVN], periaqueductal gray [PAG] and ventral tegmental area [VTA]). Females that were responsive to SD photoperiods (SD-R) and LD females given timed melatonin injections (Mel-T) exhibited gonadal regression and reduced circulating E2 , but increased aggression and circulating dehydroepiandrosterone (DHEA). Furthermore, aggressive challenges differentially altered circulating hormone profiles across seasonal phenotypes; reproductively inactive females (ie, SD-R and Mel-T females) reduced circulating DHEA and T, but increased E2 after an aggressive interaction, whereas reproductively active females (ie, LD females, SD non-responder females and LD females given mis-timed melatonin injections) solely increased circulating E2 . Although no differences in neural ARO abundance were observed, LD and SD-R females showed distinct associations between ARO cell density and aggressive behaviour in the PVN, PAG and VTA. Taken together, these results suggest that melatonin increases non-breeding aggression by elevating circulating steroid metabolism after an aggressive encounter and by regulating behaviourally relevant neural circuits in a region-specific manner.
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Affiliation(s)
- Nikki M Rendon
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | | | - Kathleen M Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Andrea C Amez
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Daniel L Boyes
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
| | - Marcy A Kingsbury
- Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, USA
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14
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Mishra I, Pullum KB, Thayer DC, Plummer ER, Conkright BW, Morris AJ, O'Hara BF, Demas GE, Ashley NT. Chemical sympathectomy reduces peripheral inflammatory responses to acute and chronic sleep fragmentation. Am J Physiol Regul Integr Comp Physiol 2020; 318:R781-R789. [PMID: 32130024 DOI: 10.1152/ajpregu.00358.2019] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Sleep loss contributes to the development of cardiovascular, metabolic, and neurological disorders by promoting a systemic proinflammatory phenotype. The neuroendocrine-immune mechanisms contributing to such pathologies are poorly understood. The sympathetic nervous system (SNS) regulates immunity and is often activated following sleep disturbances. The aims of this study were to determine 1) the effect of SNS inhibition on inflammatory responses to sleep fragmentation (SF) and 2) whether homeostasis can be restored after 1 wk of recovery sleep. We measured stress responses (norepinephrine and corticosterone), gene expression levels of pro- and anti-inflammatory cytokines in peripheral (heart, liver, and spleen) tissues, and protein levels of cytokines and chemokines in serum of female mice that were subjected to acute SF for 24 h, chronic SF for 8 wk, or 7 days of recovery after chronic SF. In each experiment, SF and control mice were chemically sympathectomized with 6-hydroxydopamine (6-OHDA) or injected with vehicle. Both acute and chronic SF elevated mRNA and protein levels of cytokines in peripheral tissues. Changes in inflammatory responses mirrored stress-axes activation, with increased corticosterone and norepinephrine in SF mice. 6-OHDA treatment significantly alleviated SF-induced inflammation, thus providing evidence of SNS regulation of peripheral inflammation from SF. Effects of chronic SF were more severe than acute SF, and 1 wk of recovery from SF sufficiently alleviated peripheral inflammatory responses but not NE responses.
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Affiliation(s)
- Ila Mishra
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | - Keelee B Pullum
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | - Domnique C Thayer
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | - Erica R Plummer
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
| | | | - Andrew J Morris
- Department of Pharmacology, University of Kentucky, Lexington, Kentucky
| | - Bruce F O'Hara
- Department of Biology, University of Kentucky, Lexington, Kentucky
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, Indiana
| | - Noah T Ashley
- Department of Biology, Western Kentucky University, Bowling Green, Kentucky
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15
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Ren CC, Sylvia KE, Munley KM, Deyoe JE, Henderson SG, Vu MP, Demas GE. Photoperiod modulates the gut microbiome and aggressive behavior in Siberian hamsters. ACTA ACUST UNITED AC 2020; 223:jeb.212548. [PMID: 31862850 DOI: 10.1242/jeb.212548] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/19/2019] [Indexed: 12/14/2022]
Abstract
Seasonally breeding animals undergo shifts in physiology and behavior in response to changes in photoperiod (day length). Interestingly, some species, such as Siberian hamsters (Phodopus sungorus), are more aggressive during the short-day photoperiods of the non-breeding season, despite gonadal regression. While our previous data suggest that Siberian hamsters employ a 'seasonal switch' from gonadal to adrenal regulation of aggression during short-day photoperiods, there is emerging evidence that the gut microbiome, an environment of symbiotic bacteria within the gastrointestinal tract, may also change seasonally and modulate social behaviors. The goal of this study was to compare seasonal shifts in the gut microbiome, circulating levels of adrenal dehydroepiandrosterone (DHEA) and aggression in male and female Siberian hamsters. Hamsters were housed in either long-day (LD) or short-day (SD) photoperiods for 9 weeks. Fecal samples were collected and behaviors were recorded following 3, 6 and 9 weeks of housing, and circulating DHEA was measured at week 9. SD females that were responsive to changes in photoperiod (SD-R), but not SD-R males, displayed increased aggression following 9 weeks of treatment. SD-R males and females also exhibited distinct changes in the relative abundance of gut bacterial phyla and families, yet showed no change in circulating DHEA. The relative abundance of some bacterial families (e.g. Anaeroplasmataceae in females) was associated with aggression in SD-R but not LD or SD non-responder (SD-NR) hamsters after 9 weeks of treatment. Collectively, this study provides insight into the complex role of the microbiome in regulating social behavior in seasonally breeding species.
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Affiliation(s)
- Clarissa C Ren
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Kristyn E Sylvia
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Kathleen M Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Jessica E Deyoe
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Sarah G Henderson
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Michael P Vu
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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16
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Munley KM, Deyoe JE, Ren CC, Demas GE. Melatonin mediates seasonal transitions in aggressive behavior and circulating androgen profiles in male Siberian hamsters. Horm Behav 2020; 117:104608. [PMID: 31669179 PMCID: PMC6980702 DOI: 10.1016/j.yhbeh.2019.104608] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/30/2019] [Accepted: 10/03/2019] [Indexed: 01/12/2023]
Abstract
Some seasonally-breeding animals are more aggressive during the short, "winter-like" days (SD) of the non-breeding season, despite gonadal regression and reduced circulating androgen levels. While the mechanisms underlying SD increases in aggression are not well understood, previous work from our lab suggests that pineal melatonin (MEL) and the adrenal androgen dehydroepiandrosterone (DHEA) are important in facilitating non-breeding aggression in Siberian hamsters (Phodopus sungorus). To characterize the role of MEL in modulating seasonal transitions in aggressive behavior, we housed male hamsters in long days (LD) or SD, treated them with timed MEL (M) or saline injections, and measured aggression after 3, 6, and 9 weeks. Furthermore, to assess whether MEL mediates seasonal shifts in gonadal and adrenal androgen synthesis, serum testosterone (T) and DHEA concentrations were quantified 36 h before and immediately following an aggressive encounter. LD-M and SD males exhibited similar physiological and behavioral responses to treatment. Specifically, both LD-M and SD males displayed higher levels of aggression than LD males and reduced circulating DHEA and T in response to an aggressive encounter, whereas LD males elevated circulating androgens. Interestingly, LD and SD males exhibited distinct relationships between circulating androgens and aggressive behavior, in which changes in serum T following an aggressive interaction (∆T) were negatively correlated with aggression in LD males, while ∆DHEA was positively correlated with aggression in SD males. Collectively, these findings suggest that SD males transition from synthesis to metabolism of circulating androgens following an aggressive encounter, a mechanism that is modulated by MEL.
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Affiliation(s)
- Kathleen M Munley
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Jessica E Deyoe
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Clarissa C Ren
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
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17
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Long KLP, Bailey AM, Greives TJ, Legan SJ, Demas GE. Endotoxin rapidly desensitizes the gonads to kisspeptin-induced luteinizing hormone release in male Siberian hamsters ( Phodopus sungorus). ACTA ACUST UNITED AC 2018; 221:jeb.185504. [PMID: 30297514 DOI: 10.1242/jeb.185504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 10/03/2018] [Indexed: 01/01/2023]
Abstract
Activation of the immune system induces rapid reductions in hypothalamic-pituitary-gonadal (HPG) axis activity, which in turn decreases secretion of sex steroids. This response is likely adaptive for survival by temporarily inhibiting reproduction to conserve energy; however, the physiological mechanisms controlling this response remain unclear. The neuropeptide kisspeptin is a candidate to mediate the decrease in sex hormones seen during sickness through its key regulation of the HPG axis. In this study, the effects of acute immune activation on the response to kisspeptin were assessed in male Siberian hamsters (Phodopus sungorus). Specifically, an immune response was induced in animals by a single treatment of lipopolysaccharide (LPS), and reproductive hormone concentrations were determined in response to subsequent injections of exogenous kisspeptin. Saline-treated controls showed a robust increase in circulating testosterone in response to kisspeptin; however, this response was blocked in LPS-treated animals. Circulating luteinizing hormone (LH) levels were elevated in response to kisspeptin in both LPS- and saline-treated groups and, thus, were unaffected by LPS treatment, suggesting gonad-level inhibition of testosterone release despite central HPG activation. In addition, blockade of glucocorticoid receptors by mifepristone did not attenuate the LPS-induced inhibition of testosterone release, suggesting that circulating glucocorticoids do not mediate this phenomenon. Collectively, these findings reveal that acute endotoxin exposure rapidly renders the gonads less sensitive to HPG stimulation, thus effectively inhibiting sex hormone release. More broadly, these results shed light on the effects of immune activation on the HPG axis and help elucidate the mechanisms controlling energy allocation and reproduction.
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Affiliation(s)
- Kimberly L P Long
- Department of Biology, Indiana University, 1001 E 3rd Street, Bloomington, IN 47405, USA
| | - Allison M Bailey
- Department of Biology, Indiana University, 1001 E 3rd Street, Bloomington, IN 47405, USA
| | - Timothy J Greives
- Biological Sciences, North Dakota State University, 1340 Bolley Drive, 201 Stevens Hall, Fargo, ND 58102, USA
| | - Sandra J Legan
- Department of Physiology, University of Kentucky, MS601 Medical Science Building, Lexington, KY 40536, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, 1001 E 3rd Street, Bloomington, IN 47405, USA
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18
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Abstract
Past research has found menstrual-cycle-related changes in functional immune response; we examined if sexual activity also changed markers of immune defense. We followed 32 naturally cycling women (15 sexually active with a partner ≥ 1 time/week, 17 sexually abstinent for the last four months) over one menstrual cycle. Participants provided serum and saliva samples at menses and ovulation, and additional saliva samples at midfollicular and midluteal phases. At each phase, participants also self-reported symptoms associated with colds, flu, pain, menstrual discomfort, and premenstrual syndrome. We tested saliva and serum for ability to kill Escherichia coli or Candida albicans, and serum for complement protein activity. For serum-mediated pathogen killing, among sexually active women only, there was a significant midcycle decrease in killing of E. coli. For saliva-mediated pathogen killing, among abstinent women only, there was a significant midcycle decrease in killing of E. coli, and midcycle increase in killing of C. albicans. Sexually active women had significantly lower complement activity than abstinent women overall. Finally, both groups reported lower physical symptoms at midcycle and higher symptoms at menses. There may be important differences in immune function between healthy women who are sexually active versus abstinent. Further replication is warranted.
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Affiliation(s)
- Tierney K Lorenz
- a Department of Psychological Science , University of North Carolina at Charlotte
- b The Kinsey Institute , Indiana University
- c Center for Integrative Study for Animal Behavior , Indiana University
| | - Julia R Heiman
- b The Kinsey Institute , Indiana University
- d Department of Psychological and Brain Sciences , Indiana University
| | - Gregory E Demas
- c Center for Integrative Study for Animal Behavior , Indiana University
- e Department of Biology , Indiana University
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19
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Sylvia KE, Deyoe JE, Demas GE. Early-life sickness may predispose Siberian hamsters to behavioral changes following alterations of the gut microbiome in adulthood. Brain Behav Immun 2018; 73:571-583. [PMID: 29981426 PMCID: PMC6607895 DOI: 10.1016/j.bbi.2018.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2018] [Revised: 06/21/2018] [Accepted: 07/01/2018] [Indexed: 12/24/2022] Open
Abstract
Although it is well-established that the immune system plays an important role in the development of physiology and behavior, the gut microbiome has recently become of interest in the study of developmental origins of behavior. Studies suggest that the effects of early-life immune activation may not occur until a secondary stressor is introduced, though the precise nature and timing of the stressor may be critical in the response. Further, recent work suggests that the microbiome and the immune system develop in parallel, and therefore any perturbations to one of these systems early in life will likely affect the other. Here, we sought to determine whether early-life activation of the immune system had long-term consequences on how the gut microbiome responds to antibiotic treatment in adulthood and whether those changes influence adult same-sex social behavior. In order to test the hypothesis that an early-life immune challenge makes individuals more vulnerable to the effects of antibiotics, we mimicked an early-life infection by injecting pups at postnatal day 3 and 5 with lipopolysaccharide (LPS; cell wall component of gram-negative bacteria) or saline, and subsequently exposed the same animals to antibiotic treatment (known to influence microbial community composition and behavior) or water in adulthood. We tracked physiology across development, and paired males and females with a novel individual of the same age and sex in adulthood to score same-sex behavior (e.g., aggression, investigation, grooming) before antibiotic treatment, immediately following treatment, and after recovery from antibiotics. LPS-treated females exhibited impaired reproductive physiology and function in adulthood (e.g., smaller ovaries and abnormal estrous cycles), and female and male gut microbial communities were strongly affected by antibiotic treatment in adulthood, but only slightly affected by postnatal LPS alone. Interestingly, LPS-treated males exhibited more robust changes in their behavioral response following adult antibiotic treatment, including decreased investigation and increased grooming, suggestive of changes in anxiety-like behaviors. These data suggest that males may be more vulnerable than females to behavioral abnormalities after being predisposed to an immune challenge early in life. Collectively, these results provide novel evidence that some of the sex-specific behavioral consequences of an early-life immune challenge may not transpire until an individual is faced with a secondary challenge, and the context in which an individual is exposed can greatly influence the response.
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Affiliation(s)
- Kristyn E. Sylvia
- Corresponding author at: Department of Biology, Indiana University, 1001 E. 3 Street, Bloomington, IN 47405, USA. (K.E. Sylvia)
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20
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Sylvia KE, Deyoe JE, Demas GE. Early‐Life Sickness May Predispose Individuals to Behavioral Changes Following Gut Dysbiosis in Adulthood. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.lb230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Sylvia KE, Lorenz TK, Heiman JR, Demas GE. Physiological predictors of leptin vary during menses and ovulation in healthy women. Reprod Biol 2018; 18:132-136. [PMID: 29454804 PMCID: PMC6310005 DOI: 10.1016/j.repbio.2018.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 01/17/2018] [Accepted: 01/28/2018] [Indexed: 12/21/2022]
Abstract
Although research has shown interactions between the reproductive system and energy homeostasis, it is not clear how environmental or behavioral factors may factor into these associations. Here we aimed to determine how changes in reproductive state (i.e., phase of the menstrual cycle) and other behavioral and physiological factors may influence leptin levels in healthy women, as well as how sexual activity may play a role in leptin modulation. We collected serum and saliva from 32 healthy women and measured leptin, estradiol, and progesterone. Participants also completed surveys of demographics, health and sexual behaviors, and physical activity. Leptin was predicted by meals per day and missed meals at both menses and ovulation. However, estradiol and physical activity were stronger predictors of leptin at menses, while sexual activity was a stronger predictor of leptin at ovulation. These findings suggest that predictors of serum leptin, and possibly energy storage and expenditure, vary across the menstrual cycle.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Tierney K Lorenz
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Kinsey Institute for Research on Sex, Gender, and Reproduction, Indiana University, Bloomington, IN 47405, USA
| | - Julia R Heiman
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Kinsey Institute for Research on Sex, Gender, and Reproduction, Indiana University, Bloomington, IN 47405, USA; Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Kinsey Institute for Research on Sex, Gender, and Reproduction, Indiana University, Bloomington, IN 47405, USA
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22
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Sylvia KE, Demas GE. Acute intraperitoneal lipopolysaccharide influences the immune system in the absence of gut dysbiosis. Physiol Rep 2018; 6:e13639. [PMID: 29536642 PMCID: PMC5849581 DOI: 10.14814/phy2.13639] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 02/12/2018] [Indexed: 12/17/2022] Open
Abstract
There is bidirectional communication between the immune system and the gut microbiome, however the precise mechanisms regulating this crosstalk are not well understood. Microbial-associated molecular patterns (MAMPs) within the gut, including lipopolysaccharide (LPS) that produces a quick and robust activation of the immune system, may be one way by which these interactions occur. Endogenous levels of LPS in the gut are low enough that they do not usually cause disease, although, in times of increased LPS loads, they may be capable of increasing vulnerability of the gut to pathogenic bacteria. Furthermore, chronic, low-grade inflammation can have lasting effects on the gut, but the effects of acute inflammation on gut communities have not been thoroughly assessed. In this study, we first investigated whether a single modest dose of LPS administered to adult male and female Siberian hamsters (Phodopus sungorus) activated the immune system by measuring levels of circulating cortisol and the proinflammatory cytokine TNF-α in the liver compared with saline-treated animals. We then investigated whether this same acute dose of LPS altered the microbiome 48 h after treatment. We found that, although LPS increased cortisol and liver cytokine levels, and produced changes in food intake and body mass in both sexes, immunological changes were independent of gut dysbiosis 48 h after LPS injection. These data suggest that an acute immune activation may not be capable of altering the gut microbiome in healthy individuals. It is likely, however, that this type of immune challenge may have other physiological impacts on the gut's vulnerability, and future studies will investigate these relationships further.
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Affiliation(s)
- Kristyn E. Sylvia
- Department of BiologyIndiana UniversityBloomingtonIndiana
- Center for the Integrative Study of Animal BehaviorIndiana UniversityBloomingtonIndiana
| | - Gregory E. Demas
- Department of BiologyIndiana UniversityBloomingtonIndiana
- Center for the Integrative Study of Animal BehaviorIndiana UniversityBloomingtonIndiana
- Program in NeuroscienceIndiana UniversityBloomingtonIndiana
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Abstract
The expression of a wide range of social and affective behaviors, including aggression and investigation, as well as anxiety- and depressive-like behaviors, involves interactions among many different physiological systems, including the neuroendocrine and immune systems. Recent work suggests that the gut microbiome may also play a critical role in modulating behavior and likely functions as an important integrator across physiological systems. Microbes within the gut may communicate with the brain via both neural and humoral pathways, providing numerous avenues of research in the area of the gut-brain axis. We are now just beginning to understand the intricate relationships among the brain, microbiome, and immune system and how they work in concert to influence behavior. The effects of different forms of experience (e.g., changes in diet, immune challenge, and psychological stress) on the brain, gut microbiome, and the immune system have often been studied independently. Though because these systems do not work in isolation, it is essential to shift our focus to the connections among them as we move forward in our investigations of the gut-brain axis, the shaping of behavioral phenotypes, and the possible clinical implications of these interactions. This review summarizes the recent progress the field has made in understanding the important role the gut microbiome plays in the modulation of social and affective behaviors, as well as some of the intricate mechanisms by which the microbiome may be communicating with the brain and immune system.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Sylvia KE, Báez Ramos P, Demas GE. Sickness-induced changes in physiology do not affect fecundity or same-sex behavior. Physiol Behav 2018; 184:68-77. [PMID: 29127071 PMCID: PMC5753605 DOI: 10.1016/j.physbeh.2017.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 11/04/2017] [Accepted: 11/04/2017] [Indexed: 12/14/2022]
Abstract
Previous work in our lab has shown that early-life infection affects female reproductive physiology and function (i.e., smaller ovaries, abnormal estrous cycles) and alters investigation and aggression towards male conspecifics in a reproductive context. Although many studies have investigated the effects of postnatal immune challenge on physiological and behavioral development, fewer studies have examined whether these changes have ultimate effects on reproduction. In the current study, we paired Siberian hamsters (Phodopus sungorus) and simulated a bacterial infection in early life by administering lipopolysaccharide (LPS) to male and female pups on pnd3 and pnd5. In adulthood, hamsters were paired with novel individuals of the same sex, and we scored an array of social behaviors (e.g., investigation, aggression). We then paired animals with individuals of the opposite sex for 5 consecutive nights, providing them with the opportunity to mate. We found that females exhibited impaired reproductive physiology and function in adulthood (i.e., smaller ovaries and abnormal estrous cycles), similar to our previous work. However, both LPS-treated males and females exhibited similar same-sex social behavior when compared with saline-treated controls, they successfully mated, and there were no significant changes in fecundity. These data suggest that the physiological changes in response to neonatal immune challenge may not have long-term effects on reproductive success in a controlled environment. Collectively, the results of this study are particularly important when investigating the relationships between physiology and behavior within an ultimate context. Animals exposed to early-life stress may in fact be capable of compensating for changes in physiology in order to survive and reproduce in some contexts.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Patricia Báez Ramos
- Biology Department, University of Puerto Rico at Mayagüez, Mayagüez, PR 00681, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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25
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Munley KM, Rendon NM, Demas GE. Neural Androgen Synthesis and Aggression: Insights From a Seasonally Breeding Rodent. Front Endocrinol (Lausanne) 2018; 9:136. [PMID: 29670576 PMCID: PMC5893947 DOI: 10.3389/fendo.2018.00136] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 03/15/2018] [Indexed: 11/24/2022] Open
Abstract
Aggression is an essential social behavior that promotes survival and reproductive fitness across animal systems. While research on the neuroendocrine mechanisms underlying this complex behavior has traditionally focused on the classic neuroendocrine model, in which circulating gonadal steroids are transported to the brain and directly mediate neural circuits relevant to aggression, recent studies have suggested that this paradigm is oversimplified. Work on seasonal mammals that exhibit territorial aggression outside of the breeding season, such as Siberian hamsters (Phodopus sungorus), has been particularly useful in elucidating alternate mechanisms. These animals display elevated levels of aggression during the non-breeding season, in spite of gonadal regression and reduced levels of circulating androgens. Our laboratory has provided considerable evidence that the adrenal hormone precursor dehydroepiandrosterone (DHEA) is important in maintaining aggression in both male and female Siberian hamsters during the non-breeding season, a mechanism that appears to be evolutionarily-conserved in some seasonal rodent and avian species. This review will discuss research on the neuroendocrine mechanisms of aggression in Siberian hamsters, a species that displays robust neural, physiological, and behavioral changes on a seasonal basis. Furthermore, we will address how these findings support a novel neuroendocrine pathway for territorial aggression in seasonal animals, in which adrenal DHEA likely serves as an essential precursor for neural androgen synthesis during the non-breeding season.
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Abstract
Sickness is typically characterized by fever, anorexia, cachexia, and reductions in social, pleasurable, and sexual behaviors. These responses can be displayed at varying intensities both within and among individuals, and the adaptive nature of sickness responses can be demonstrated by the context-dependent nature of their expression. The study of sickness has become an important area of investigation for researchers in a wide range of areas, including psychoneuroimmunology (PNI) and ecoimmunology (EI). The general goal of PNI is to identify key interactions among the nervous, endocrine and immune systems and behavior, and how disruptions in these processes might contribute to disease states. EI, in turn, has been established more recently within the perspectives of ecology and evolutionary biology, and is aimed more at understanding natural variation in immune function and sickness responses within a broadly integrative, organismal, and evolutionary context. The goal of this review is to examine the literature on sickness from both basic and biomedical perspectives within PNI and EI and to demonstrate how the integrative study of sickness behavior can serve as an integrating agent to connect ecological and translational approaches to the study of disease. By focusing on a set of specific exemplars, including the energetics of sickness, social context, and environmental influences on sickness, we hope to accomplish the larger goal of developing a common synthetic framework to understand sickness from multiple levels of analysis and varying perspectives across the fields of PNI and EI. By applying this integrative approach to sickness, we will be able to develop a more comprehensive view of sickness as a suite of adaptive responses rather than the simply deleterious consequences of illness.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology, Center for the Integrative Study of Animal Behavior, and Program in Neuroscience Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, and Program in Neuroscience Indiana University, Bloomington, IN 47405, USA
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Affiliation(s)
- Rachel M. Bowden
- School of Biological Sciences; Illinois State University; Normal Illinois USA
| | | | - Gregory E. Demas
- Department of Biology; Indiana University; Bloomington Indiana USA
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Bailey AM, Legan SJ, Meretsky VJ, Demas GE. Effects of exogenous leptin on seasonal reproductive responses to interacting environmental cues in female Siberian hamsters. Gen Comp Endocrinol 2017; 250:95-103. [PMID: 28619288 DOI: 10.1016/j.ygcen.2017.06.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 06/09/2017] [Accepted: 06/10/2017] [Indexed: 11/19/2022]
Abstract
Animals living in temperate climates respond to environmental cues that signal current and future resource availability to ensure that energy resources are available to support reproduction. Siberian hamsters (Phodopus sungorus) undergo robust gonadal regression in short, winter-like photoperiods as well as in response to mild food restriction in intermediate photoperiods. The goal of the present study was to investigate whether leptin is a relevant metabolic signal in regulating gonadal regression in response to diminishing food availability. Adult female hamsters housed in short-day (winter-like) or intermediate (fall-like) photoperiods received either ad libitum access to food or mild food restriction (90% of ad libitum intake) and were treated with either leptin or a vehicle for five weeks in order to determine the ability of leptin to inhibit gonadal regression. At the end of five weeks, vehicle-treated hamsters showed physiological signs associated with ongoing gonadal regression, such as decreases in body mass and food intake, cessation of estrous cycling, and small decreases in reproductive tissue mass. Leptin did not modify changes in body mass, food intake, hormone concentration, or tissue mass, but showed a tendency to support estrous cycling, particularly in response to food restriction in the intermediate photoperiod treatment. Overall, leptin appears to play a minor role in coordinating reproductive responses to multiple environmental cues, at least in the early stages of gonadal regression.
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Affiliation(s)
- Allison M Bailey
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
| | - Sandra J Legan
- Department of Physiology, University of Kentucky, 508 Medical Science Building, Lexington, KY, USA.
| | - Vicky J Meretsky
- School of Public and Environmental Affairs, Indiana University, 315 E 10th St., Bloomington, IN, USA.
| | - Gregory E Demas
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
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Sylvia KE, Demas GE. Overcoming neonatal sickness: Sex-specific effects of sickness on physiology and social behavior. Physiol Behav 2017; 179:324-332. [PMID: 28689742 DOI: 10.1016/j.physbeh.2017.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 06/11/2017] [Accepted: 07/01/2017] [Indexed: 12/13/2022]
Abstract
Early-life environmental stressors, including sickness, have the potential to disrupt development in ways that could severely impact fitness. Despite what is known about the effects of sickness on reproduction, the precise physiological mechanisms have not yet been determined. The goal of this study was to investigate the effects of a neonatal immune challenge on adult reproductive physiology and opposite-sex social behavior. Male and female Siberian hamster (Phodopus sungorus) pups were administered lipopolysaccharide ([LPS]; a cell wall component of gram-negative bacteria) or saline injections on postnatal days 3 and 5 and body mass, food intake, and measures of reproductive maturity were taken throughout development. In adulthood, hamsters were placed in staged mating pairs with reproductively mature individuals of the opposite sex, during which a series of behaviors were scored. We found that although males and females showed no change in food intake, body mass, or reproductive behaviors, LPS-treated females had abnormal estrous cycles and smaller ovaries. Females also showed increased investigation of and increased aggression towards males in a reproductive context. In contrast, LPS-treated males showed no change in any physiological measures, nor did they show any changes in behavior. The present findings demonstrate that females may be more robustly affected by neonatal sickness than males and that these effects could have potential impacts on reproductive success. Collectively, the results of this study can be used to expand upon what is already known about sickness and reproduction, specifically the importance of social behaviors involved in pre-copulation and information necessary to choose the appropriate mate.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Ho JM, Bergeon Burns CM, Rendon NM, Rosvall KA, Bradshaw HB, Ketterson ED, Demas GE. Lipid signaling and fat storage in the dark-eyed junco. Gen Comp Endocrinol 2017; 247:166-173. [PMID: 28161439 PMCID: PMC5410188 DOI: 10.1016/j.ygcen.2017.01.029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 12/13/2016] [Accepted: 01/28/2017] [Indexed: 12/11/2022]
Abstract
Seasonal hyperphagia and fattening promote survivorship in migratory and wintering birds, but reduced adiposity may be more advantageous during the breeding season. Factors such as photoperiod, temperature, and food predictability are known environmental determinants of fat storage, but the underlying neuroendocrine mechanisms are less clear. Endocannabinoids and other lipid signaling molecules regulate multiple aspects of energy balance including appetite and lipid metabolism. However, these functions have been established primarily in mammals; thus the role of lipid signals in avian fat storage remains largely undefined. Here we examined relationships between endocannabinoid signaling and individual variation in fat storage in captive white-winged juncos (Junco hyemalis aikeni) following a transition to long-day photoperiods. We report that levels of the endocannabinoid 2-arachidonoylglycerol (2-AG), but not anandamide (AEA), in furcular and abdominal fat depots correlate negatively with fat mass. Hindbrain mRNA expression of CB1 endocannabinoid receptors also correlates negatively with levels of fat, demonstrating that fatter animals experience less central and peripheral endocannabinoid signaling when in breeding condition. Concentrations of the anorexigenic lipid, oleoylethanolamide (OEA), also inversely relate to adiposity. These findings demonstrate unique and significant relationships between adiposity and lipid signaling molecules in the brain and periphery, thereby suggesting a potential role for lipid signals in mediating adaptive levels of fat storage.
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Affiliation(s)
- Jacqueline M Ho
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Christine M Bergeon Burns
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Nikki M Rendon
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Kimberly A Rosvall
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Heather B Bradshaw
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA; Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN 47405, USA
| | - Ellen D Ketterson
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA; Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Rendon NM, Amez AC, Proffitt MR, Bauserman ER, Demas GE. Aggressive behaviours track transitions in seasonal phenotypes of female Siberian hamsters. Funct Ecol 2017; 31:1071-1081. [PMID: 28757672 PMCID: PMC5526640 DOI: 10.1111/1365-2435.12816] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Seasonally breeding animals exhibit profound physiological and behavioural responses to changes in ambient day length (photoperiod), including changes in reproductive function and territorial aggression.Species where aggression persists when gonads are regressed and circulating levels of gonadal hormones are low, such as Siberian hamsters (Phodopus sungorus) and song sparrows (Melospiza melodia), challenge the well-established framework that gonadal hormones are important mediators of aggression.A solution to this apparent paradox is that a season-specific increase in sensitivity to hormones in brain areas associated with aggression offsets low levels of gonadal hormones during periods of reproductive quiescence.To test this hypothesis, we manipulated photoperiod to induce natural fluctuations in seasonal phenotype across multiple stages of the annual reproductive cycle in female Siberian hamsters that display increased aggression during short-day reproductive quiescence, suggesting that behaviour persists independent of gonadal steroids.Females were housed in long "summer" days or short "winter" days for 10, 24 or 30 weeks to capture gonadal regression, transition back to a reproductively functional state and full gonadal recrudescence, respectively.Long-day animals maintained reproductive functionality and displayed low aggression across all time points. By week 10, short-day reproductively responsive females underwent gonadal regression and displayed increased aggression; non-responsive animals showed no such changes. At week 24, animals were in a transitional period and displayed an intermediate phenotype with respect to reproduction and aggression. By week 30, short-day females were fully recrudesced and returned to long-day-like levels of aggression.Consistent with our hypothesis, gonadally regressed females displayed decreases in 17β-oestradiol (oestradiol) levels, but site-specific increases in the abundance of brain oestrogen receptor-alpha (ERα) in regions associated with aggression, but not reproduction. Increased site-specific ERα may function as a compensatory mechanism to allow increased responsiveness to oestradiol in regulating aggression in lieu of high circulating concentrations of hormones.Collectively, these results broaden our understanding of how breeding phenology maps onto social behaviour and the mechanisms that have evolved to coordinate behaviours that occur in non-breeding contexts.
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Affiliation(s)
- Nikki M Rendon
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Andrea C Amez
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Melissa R Proffitt
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Elizabeth R Bauserman
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Affiliation(s)
| | - Sandra J. Legan
- Department of Physiology University of Kentucky Lexington KY USA
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Sylvia KE, Jewell CP, Rendon NM, St John EA, Demas GE. Sex-specific modulation of the gut microbiome and behavior in Siberian hamsters. Brain Behav Immun 2017; 60:51-62. [PMID: 27816476 DOI: 10.1016/j.bbi.2016.10.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Revised: 09/28/2016] [Accepted: 10/16/2016] [Indexed: 12/12/2022] Open
Abstract
The gut microbiome is a diverse, host-specific, and symbiotic bacterial environment that is critical for mammalian survival and exerts a surprising yet powerful influence on brain and behavior. Gut dysbiosis has been linked to a wide range of physical and psychological disorders, including autism spectrum disorders and anxiety, as well as autoimmune and inflammatory disorders. A wealth of information on the effects of dysbiosis on anxiety and depression has been reported in laboratory model systems (e.g., germ-free mice); however, the effects of microbiome disruption on social behaviors (e.g., aggression) of non-model species that may be particularly important in understanding many aspects of physiology and behavior have yet to be fully explored. Here we assessed the sex-specific effects of a broad-spectrum antibiotic on the gut microbiome and its effects on social behaviors in male and female Siberian hamsters (Phodopus sungorus). In Experiment 1, we administered a broad-spectrum antibiotic on a short-term basis and found that antibiotic treatment altered the microbial communities in the gut in male and female hamsters. In Experiment 2, we tested the effects of single versus repeated antibiotic treatment (including a recovery phase) on behavior, and found that two, but not one, treatments caused marked decreases in aggressive behavior, but not other social behaviors, in males; aggression returned to normal levels following recovery. Antibiotic-treated females, in contrast, showed decreased aggression after a single treatment, with all other social behaviors unaffected. Unlike males, female aggression did not return to normal during either recovery period. The present findings demonstrate that modest antibiotic treatment results in marked disruption of the gut microbiome in hamsters, akin to research done in other rodent species and humans. Further, we show that treatment with a broad-spectrum antibiotic, which has dysbiotic effects, also has robust, sex-specific effects on aggression, a critical behavior in the survival and reproductive success of many rodent species.
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Affiliation(s)
- Kristyn E Sylvia
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Cathleen P Jewell
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Nikki M Rendon
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Emma A St John
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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Abstract
Although testosterone (T) has been characterized as universally immunosuppressive across species and sexes, recent ecoimmunology research suggests that T's immunomodulatory effects (enhancing/suppressing) depend on the organism's reproductive context. Very little is known about the immune effects of T in healthy females, and even less about how reproductive effort modulates the immune effects of T in humans. We investigated how the interaction between endogenous T and sexual activity predicted menstrual cycle-related changes in several measures of immunity: inflammation (indexed by interleukin-6, IL-6), adaptive immunity (indexed by immunoglobulin A, IgA), and functional immunity (indexed by bactericidal assay). Thirty-two healthy women (sexually abstinent, N=17; sexually active with one male partner, N=15) provided saliva samples at four points in the menstrual cycle: menses, follicular, ovulation, and luteal phases. Among sexually abstinent women, T was positively associated with IL-6 across the cycle; for sexually active women, however, T was positively associated with IL-6 in the luteal phase only, and negatively associated with IL-6 at ovulation. High T predicted higher IgA among women who reported infrequent intercourse, but lower IgA among women who reported very frequent intercourse. Finally, across groups, T was positively associated with greater bacterial killing at menses, but negatively associated in the luteal phase. Overall, rather than being universally immunosuppressive, T appeared to signal immunomodulation relevant to reproduction (e.g., lowering inflammation at ovulation, potentially preventing immune interference with conception). Our findings support the hypothesis that the immunomodulatory effects of endogenous T in healthy females depend on sexual and reproductive context.
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Affiliation(s)
- Tierney K Lorenz
- Center for Integrative Study for Animal Behavior, Indiana University, 409 N. Park Ave, Bloomington, IN 47405, United States; The Kinsey Institute, Indiana University, 1165 E 3rd St., Bloomington, IN 47405, United States; Department of Psychology, University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223, United States.
| | - Julia R Heiman
- Center for Integrative Study for Animal Behavior, Indiana University, 409 N. Park Ave, Bloomington, IN 47405, United States; The Kinsey Institute, Indiana University, 1165 E 3rd St., Bloomington, IN 47405, United States; Department of Psychological and Brain Sciences, Indiana University, 1101 E. 10th St., Bloomington, IN 47405, United States.
| | - Gregory E Demas
- Center for Integrative Study for Animal Behavior, Indiana University, 409 N. Park Ave, Bloomington, IN 47405, United States; Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN 47405, United States.
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Affiliation(s)
- Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA.
| | - Noah T Ashley
- Department of Biology, Western Kentucky University, Bowling Green, KY 42101, USA
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Abstract
Mounting a sickness response is an energetically expensive task and requires precise balancing of energy allocation to ensure pathogen clearance while avoiding compromising energy reserves. Sickness intensity has previously been shown to be modulated by food restriction, body mass, and hormonal signals of energy. In the current study, we tested the hypothesis that sickness intensity is modulated by glucose availability and an endocrine signal of glucose availability, insulin. We utilized male Siberian hamsters (Phodopus sungorus) and predicted that pharmacological induction of glucoprivation with 2-deoxy-d-glucose (2-DG), a non-metabolizable glucose analog that disrupts glycolysis, would attenuate energetically expensive sickness symptoms. Alternatively, we predicted that treatment of animals with insulin would enhance energetically expensive sickness symptoms, as insulin would act as a signal of increased glucose availability. Upon experimental treatment with lipopolysaccharide (LPS), we found that glucose deprivation resulted in increased sickness-induced hypothermia as compared to control- and insulin-treated animals; however, it did not have any effects on sickness-induced anorexia or body mass loss. Insulin treatment resulted in an unexpectedly exaggerated sickness response in animals of lesser body masses; however, in animals of greater body masses, insulin actually attenuated sickness-induced body mass loss and had no effects on hypothermia or anorexia. The effects of insulin on sickness severity may be modulated by sensitivity to sickness-induced hypoglycemia. Collectively, these results demonstrate that both glucose availability and signals of glucose availability can modulate the intensity of energetically expensive sickness symptoms, but their effects differ among different sickness symptoms and are sensitive to energetic context.
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Affiliation(s)
- Elizabeth D Carlton
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Gregory E Demas
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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Abstract
Multidirectional interactions among the immune, endocrine, and nervous systems have been demonstrated in humans and non-human animal models for many decades by the biomedical community, but ecological and evolutionary perspectives are lacking. Neuroendocrine-immune interactions can be conceptualized using a series of feedback loops, which culminate into distinct neuroendocrine-immune phenotypes. Behavior can exert profound influences on these phenotypes, which can in turn reciprocally modulate behavior. For example, the behavioral aspects of reproduction, including courtship, aggression, mate selection and parental behaviors can impinge upon neuroendocrine-immune interactions. One classic example is the immunocompetence handicap hypothesis (ICHH), which proposes that steroid hormones act as mediators of traits important for female choice while suppressing the immune system. Reciprocally, neuroendocrine-immune pathways can promote the development of altered behavioral states, such as sickness behavior. Understanding the energetic signals that mediate neuroendocrine-immune crosstalk is an active area of research. Although the field of psychoneuroimmunology (PNI) has begun to explore this crosstalk from a biomedical standpoint, the neuroendocrine-immune-behavior nexus has been relatively underappreciated in comparative species. The field of ecoimmunology, while traditionally emphasizing the study of non-model systems from an ecological evolutionary perspective, often under natural conditions, has focused less on the physiological mechanisms underlying behavioral responses. This review summarizes neuroendocrine-immune interactions using a comparative framework to understand the ecological and evolutionary forces that shape these complex physiological interactions.
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Affiliation(s)
- Noah T Ashley
- Department of Biology, Western Kentucky University, Bowling Green, KY 42101, USA.
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior - Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Lorenz TK, Demas GE, Heiman JR. Partnered sexual activity moderates menstrual cycle-related changes in inflammation markers in healthy women: an exploratory observational study. Fertil Steril 2016; 107:763-773.e3. [PMID: 27919440 DOI: 10.1016/j.fertnstert.2016.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 11/09/2016] [Accepted: 11/10/2016] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To examine differences in inflammation markers in sexually active versus abstinent women and observe changes in inflammation markers across the menstrual cycle. Cycle-related immune fluctuations may have evolved to reduce interference with conception. If so, reproductively active (i.e., sexually active) women should show the most variability in cytokine expression. DESIGN Participants provided serum samples at menses and ovulation (from which cytokines were assayed) and saliva samples at menses and during follicular, ovulation, and luteal phases (from which C-reactive protein [CRP] was assayed). Participants self-reported intercourse frequency during the study. SETTING Academic research laboratory. PATIENT(S) Thirty-two healthy, naturally cycling premenopausal women (sexually active, n = 15; abstinent, n = 17). INTERVENTION(S) Observational study. MAIN OUTCOME MEASURE(S) Levels of proinflammatory cytokines (interleukin-6 [IL-6], interferon γ [IFN-γ], tumor necrosis factor-α [TNF-α]), an anti-inflammatory cytokine (interleukin-4 [IL-4]), and a marker of total inflammation (CRP). RESULT(S) Sexually active women had higher levels of all of the immune markers measured, including both pro- and anti-inflammatory cytokines, than abstinent women. Relative to sexually active women, abstinent women had less change across the menstrual cycle in levels of CRP. Among sexually active women, higher intercourse frequency predicted greater midcycle decreases in CRP, IL-6, and IFN-γ and midcycle increases in IL-4. CONCLUSION(S) Sexual activity may stimulate a complex interaction between pro- and anti-inflammatory cytokines that subsequently drives midcycle declines in inflammation.
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Affiliation(s)
- Tierney K Lorenz
- Kinsey Institute, Indiana University, Bloomington, Indiana; Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Department of Psychology, University of North Carolina at Charlotte, Charlotte, North Carolina.
| | - Gregory E Demas
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Department of Biology, Indiana University, Bloomington, Indiana
| | - Julia R Heiman
- Kinsey Institute, Indiana University, Bloomington, Indiana; Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana
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Bailey AM, Rendon NM, O'Malley KJ, Demas GE. Food as a supplementary cue triggers seasonal changes in aggression, but not reproduction, in Siberian hamsters. Physiol Behav 2016; 167:298-308. [PMID: 27693590 DOI: 10.1016/j.physbeh.2016.09.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/12/2016] [Accepted: 09/26/2016] [Indexed: 11/18/2022]
Abstract
Animals living in temperate regions prepare for harsh winter conditions by responding to environmental cues that signal resource availability (e.g., food, day length). Siberian hamsters (Phodopus sungorus) breed in long, summer-like days (LD, >14h light), i.e., photoperiods, and undergo robust gonadal regression and become more aggressive when exposed to short, winter-like photoperiods that signal impending limited resources (SD, <10h light). When hamsters are reared within an intermediate photoperiod (ID, 13.5h light), they are reproductively active, but undergo gonadal regression in response to mild food restriction (FR) over 6-12weeks. We hypothesized that short-term (1-2weeks) FR in an ID photoperiod would provide a signal of impending limited resources and initiate the seasonal increase in aggression typical of SD photoperiods, as well as alter reproductive behaviors in advance of gonadal regression. To test this, we housed male and female hamsters in LD or ID photoperiods, with ad libitum (AL) access to food or a 90%-AL ration. We tested aggressive behavior after one week and reproductive behavior after two weeks, and subsequently monitored females for pregnancy and litter production. Both sexes displayed increased aggression in the ID-FR treatment. Untreated male intruders were less likely to ejaculate when paired with ID females during reproductive encounters. ID-FR males were undergoing gonadal regression after two weeks, but were more likely to have ejaculated. Female pregnancy and litter characteristics were unaltered by treatment: females were equally likely to achieve pregnancy and produce comparable litters across treatment groups. Collectively, we demonstrate that a signal of diminishing resources in an ID photoperiod is sufficient to trigger seasonal aggression, but that hamsters are reproductively resilient to inhibitory environmental cues in the short term. Broadly, our findings provide an important context for exploring seasonal changes in behavior and physiology from an ultimate perspective.
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Affiliation(s)
- Allison M Bailey
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
| | - Nikki M Rendon
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
| | - Kyle J O'Malley
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
| | - Gregory E Demas
- Department of Biology, Indiana University, 1001 E 3rd St., Bloomington, IN, USA.
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Rendon NM, Rudolph LM, Sengelaub DR, Demas GE. The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens. Proc Biol Sci 2016; 282:rspb.2015.2080. [PMID: 26582025 DOI: 10.1098/rspb.2015.2080] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Classic findings have demonstrated an important role for sex steroids as regulators of aggression, but this relationship is lacking within some environmental contexts. In mammals and birds, the adrenal androgen dehydroepiandrosterone (DHEA), a non-gonadal precursor of biologically active steroids, has been linked to aggression. Although females, like males, use aggression when competing for limited resources, the mechanisms underlying female aggression remain understudied. Here, we propose a previously undescribed endocrine mechanism regulating female aggression via direct action of the pineal hormone melatonin on adrenal androgens. We examined this in a solitary hamster species, Phodopus sungorus, in which both sexes are highly territorial across the seasons, and display increased aggression concomitant with decreased serum levels of sex steroids in short 'winter-like' days. Short- but not long-day females had increased adrenal DHEA responsiveness co-occurring with morphological changes in the adrenal gland. Further, serum DHEA and total adrenal DHEA content were elevated in short days. Lastly, melatonin increased DHEA and aggression and stimulated DHEA release from cultured adrenals. Collectively, these findings demonstrate that DHEA is a key peripheral regulator of aggression and that melatonin coordinates a 'seasonal switch' from gonadal to adrenal regulation of aggression by direct action on the adrenal glands.
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Affiliation(s)
- Nikki M Rendon
- Department of Biology, Indiana University, Bloomington, IN 47405, USA Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Lauren M Rudolph
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Dale R Sengelaub
- Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Indiana University, Bloomington, IN 47405, USA Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Abstract
The combined challenge of low food availability and low temperatures can make winter difficult for survival, and nearly impossible for breeding. Traditionally, studies of seasonality have focused on reproductive adaptations and largely ignored adaptations associated with survival. We propose shifting the focus from reproduction to immune function, a proxy for survival, and hypothesize that evolved physiological and behavioral mechanisms enable individuals to anticipate recurrent seasonal stressors and enhance immune function in advance of their occurrence. These seasonal adaptations, which have an important influence on seasonal patterns of survival, are reviewed here. We then discuss studies suggesting that photoperiod (day length) and photoperiod-dependent melatonin secretion influence immune function. Our working hypothesis is that short day lengths reroute energy from reproduction and growth to bolster immune function during winter. The net effect of these photoperiod-mediated adjustments is enhanced immune function and increased survival.
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Affiliation(s)
- Randy J. Nelson
- Departments of Psychology and Neuroscience, Ohio State University, Columbus
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42
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French SS, Chester EM, Demas GE. Timing of Maternal Immunization Affects Immunological and Behavioral Outcomes of Adult Offspring in Siberian Hamsters (Phodopus sungorus). ACTA ACUST UNITED AC 2016; 325:377-89. [PMID: 27320639 DOI: 10.1002/jez.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 05/04/2016] [Accepted: 06/01/2016] [Indexed: 11/09/2022]
Abstract
Maternal influences are an important contributing factor to offspring survival, development, and behavior. Common environmental pathogens can induce maternal immune responses and affect subsequent development of offspring. There are likely sensitive periods during pregnancy when animals are particularly vulnerable to environmental disruption. Here we characterize the effects of maternal immunization across pregnancy and postpartum on offspring physiology and behavior in Siberian hamsters (Phodopus sungorus). Hamsters were injected with the antigen keyhole limpet hemocyanin (KLH) (1) prior to pairing with a male (premating), (2) at separation (postmating), (3) at midpregnancy, or (4) after birth (lactation). Maternal food intake, body mass, and immunity were monitored throughout gestation, and litters were measured weekly for growth until adulthood when social behavior, hormone concentrations, and immune responses were determined. We found that immunizations altered maternal immunity throughout pregnancy and lactation. The effects of maternal treatment differed between male and female offspring. Aggressive behavior was enhanced in offspring of both sexes born to mothers treated postmating and thus early in pregnancy relative to other stages. In contrast, maternal treatment and maternal stage differentially affected innate immunity in males and females. Offspring cortisol, however, was unaffected by maternal treatment. Collectively, these data demonstrate that maternal immunization affects offspring physiology and behavior in a time-dependent and sex-specific manner. More broadly, these findings contribute to our understanding of the effects of maternal immune activation, whether it be from environmental exposure or immunization, on immunological and behavioral responses of offspring.
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Affiliation(s)
- Susannah S French
- Department of Biology and the Ecology Center, Utah State University, Logan, Utah
| | - Emily M Chester
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, Indiana
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43
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Rendon NM, Soini HA, Scotti MAL, Weigel ER, Novotny MV, Demas GE. Photoperiod and aggression induce changes in ventral gland compounds exclusively in male Siberian hamsters. Horm Behav 2016; 81:1-11. [PMID: 26944610 DOI: 10.1016/j.yhbeh.2016.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 01/12/2016] [Accepted: 02/02/2016] [Indexed: 10/22/2022]
Abstract
Chemical communication is a critical component of social behavior as it facilitates social encounters, allows for evaluation of the social partner, defines territories and resources, and advertises information such as sex and physiological state of an animal. Odors provide a key source of information about the social environment to rodents; however, studies identifying chemical compounds have thus far focused primarily on few species, particularly the house mouse. Moreover, considerably less attention has been focused on how environmental factors, reproductive phenotype, and behavioral context alter these compounds outside of reproduction. We examined the effects of photoperiod, sex, and social context on chemical communication in the seasonally breeding Siberian hamster. We sampled ventral gland secretions in both male and female hamsters before and after an aggressive encounter and identified changes in a range of volatile compounds. Next, we investigated how photoperiod, reproductive phenotype, and aggression altered ventral gland volatile compound composition across the sexes. Males exhibited a more diverse chemical composition, more sex-specific volatiles, and showed higher levels of excretion compared to females. Individual volatiles were also differentially excreted across photoperiod and reproductive phenotype, as well as differentially altered in response to an aggressive encounter. Female volatile compound composition, in contrast, did not differ across photoperiods or in response to aggression. Collectively, these data contribute to a greater understanding of context-dependent changes in chemical communication in a seasonally breeding rodent.
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Affiliation(s)
- Nikki M Rendon
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA.
| | - Helena A Soini
- Department of Chemistry, Institute for Pheromone Research, Indiana University, Bloomington, IN 47405, USA
| | - Melissa-Ann L Scotti
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Ellen R Weigel
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Milos V Novotny
- Department of Chemistry, Institute for Pheromone Research, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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44
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Albers HE, Bittman E, Demas GE, Goldman B, Zucker I. Timothy J. Bartness. J Biol Rhythms 2016; 31:6-11. [PMID: 26759429 DOI: 10.1177/0748730415626807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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45
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Demas GE, Sylvia KE. There's no place like biome: Can helminths restore the body's ecosystem? Brain Behav Immun 2016; 51:12-13. [PMID: 26381206 DOI: 10.1016/j.bbi.2015.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 09/13/2015] [Indexed: 11/16/2022] Open
Affiliation(s)
- Gregory E Demas
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA.
| | - Kristyn E Sylvia
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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46
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Rendon NM, Demas GE. Bi‐directional actions of dehydroepiandrosterone and aggression in female Siberian hamsters. ACTA ACUST UNITED AC 2015; 325:116-21. [DOI: 10.1002/jez.2001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/03/2015] [Accepted: 12/03/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Nikki M. Rendon
- Department of BiologyCenter for the Integrative Study of Animal BehaviorProgram in NeuroscienceIndiana UniversityBloomingtonIndiana
| | - Gregory E. Demas
- Department of BiologyCenter for the Integrative Study of Animal BehaviorProgram in NeuroscienceIndiana UniversityBloomingtonIndiana
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Lorenz TK, Demas GE, Heiman JR. Interaction of menstrual cycle phase and sexual activity predicts mucosal and systemic humoral immunity in healthy women. Physiol Behav 2015; 152:92-8. [PMID: 26394125 DOI: 10.1016/j.physbeh.2015.09.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 08/14/2015] [Accepted: 09/18/2015] [Indexed: 12/23/2022]
Abstract
Several studies have documented shifts in humoral immune parameters (e.g., immunoglobulins) across the menstrual cycle in healthy women. It is thought that these shifts may reflect dynamic balancing between reproduction and pathogen defense, as certain aspects of humoral immunity may disrupt conception and may be temporarily downregulated at ovulation. If so, one could expect maximal cycle-related shifts of humoral immunity in individuals invested in reproduction - that is, women who are currently sexually active - and less pronounced shifts in women who are not reproductively active (i.e., abstinent). We investigated the interaction of sexual activity, menstrual cycle phase, and humoral immunity in a sample of 32 healthy premenopausal women (15 sexually active, 17 abstinent). Participants provided saliva samples during their menses, follicular phase, ovulation (as indicated by urine test for LH surge), and luteal phase, from which IgA was assayed. Participants also provided blood samples at menses and ovulation, from which IgG was assayed. Sexually active participants provided records of their frequency of sexual activity as well as condom use. At ovulation, sexually active women had higher IgG than abstinent women (d=0.77), with women reporting regular condom use showing larger effects (d=0.63) than women reporting no condom use (d=0.11). Frequency of sexual activity predicted changes in IgA (Cohen's f(2)=0.25), with women reporting high frequency of sexual activity showing a decrease in IgA at ovulation, while women reporting low frequency or no sexual activity showing an increase in IgA at ovulation. Taken together, these findings support the hypothesis that shifts in humoral immunity across the menstrual cycle are associated with reproductive effort, and could contribute to the mechanisms by which women's physiology navigates tradeoffs between reproduction and immunity.
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Affiliation(s)
- Tierney K Lorenz
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, 409 N Park Ave, Bloomington, IN, United States; The Kinsey Institute, Indiana University, Bloomington, 1165 E 3rd St., Bloomington, IN 47405, United States.
| | - Gregory E Demas
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, 409 N Park Ave, Bloomington, IN, United States; Department of Biology, Indiana University, Bloomington, 1001 E 3rd St, Bloomington, IN, United States; Department of Psychological and Brain Sciences, Indiana University, Bloomington, 1101 E 10th St., Bloomington, IN, United States.
| | - Julia R Heiman
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, 409 N Park Ave, Bloomington, IN, United States; The Kinsey Institute, Indiana University, Bloomington, 1165 E 3rd St., Bloomington, IN 47405, United States; Department of Psychological and Brain Sciences, Indiana University, Bloomington, 1101 E 10th St., Bloomington, IN, United States.
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48
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Rendon NM, Keesom SM, Amadi C, Hurley LM, Demas GE. Vocalizations convey sex, seasonal phenotype, and aggression in a seasonal mammal. Physiol Behav 2015; 152:143-50. [PMID: 26386405 DOI: 10.1016/j.physbeh.2015.09.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 08/30/2015] [Accepted: 09/14/2015] [Indexed: 01/22/2023]
Abstract
Seasonal variation in social behavior is often accompanied by seasonal variation in communication. In mammals, how seasonal environmental cues influence aggressive vocalizations remains underexplored. Photoperiod is the primary cue coordinating seasonal responses in most temperate zone animals, including Siberian hamsters (Phodopus sungorus), a species that undergoes reproductive inhibition and increased aggression in winter. During same-sex aggressive encounters, hamsters emit both broadband calls (BBCs) and ultrasonic vocalizations (USVs) that indicate aggression and the vocalizer's sex, respectively; however, it is not known whether these rodents adjust specific elements of their vocal repertoire to reflect their photoperiod-induced seasonal phenotypes. To address this, we recorded vocalizations emitted during dyadic interactions between male or female pairs of hamsters housed in long or short photoperiods and measured serum testosterone levels. USV emission rate remained stable across photoperiods, but proportional use of USV subtypes varied in novel ways: 'jump' USVs were sensitive to seasonal phenotype, but not the vocalizer's sex, whereas 'plain' USVs were sensitive only to the sex of the vocalizer. BBC emission rate varied with seasonal phenotype; short-day non-reproductive hamsters produced more BBCs and demonstrated increased aggression compared with reproductive hamsters. Testosterone, however, was not related to vocalization rates. Collectively, these findings demonstrate that changes in the vocal repertoire of Siberian hamsters reflect sex, aggression, and seasonal phenotype, suggesting that both BBCs and USVs are important signals used during same-sex social encounters.
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Affiliation(s)
- Nikki M Rendon
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA.
| | - Sarah M Keesom
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Chima Amadi
- Department of Animal Sciences, Cornell University, Ithaca, NY 14850, USA
| | - Laura M Hurley
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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49
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Lorenz TK, Heiman JR, Demas GE. Sexual activity modulates shifts in TH1/TH2 cytokine profile across the menstrual cycle: an observational study. Fertil Steril 2015; 104:1513-21.e1-4. [PMID: 26385401 DOI: 10.1016/j.fertnstert.2015.09.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 09/01/2015] [Accepted: 09/01/2015] [Indexed: 01/31/2023]
Abstract
OBJECTIVE To investigate if sexual activity moderated menstrual cycle-related shifts in cytokines associated with T-helper type 1 (TH1) cells (e.g., interferon [IFN] γ) and T-helper type 2 (TH2) cells (e.g., interleukin [IL] 4). Immune activity shifts across the menstrual cycle, with higher follicular-phase TH1-cell activity but higher luteal-phase TH2-cell activity. Little is known about how social behaviors alter TH1-TH2 ratios, despite evidence that psychosocial factors can influence immunity. Of particular interest is how sexual activity influences immune responses that may support conception, such as the TH1-TH2 balance. DESIGN Participants provided saliva samples at four time points (menstrual, follicular, ovulatory, and luteal phases), which were assayed by means of ELISA. SETTING Academic laboratory. PARTICIPANT(S) Thirty healthy premenopausal women (16 sexually abstinent, 14 sexually active) not taking hormonal or immunoactive medications. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Salivary E2, P, IFN-γ, and IL-4. RESULT(S) Sexually active, but not abstinent, women were significantly more likely to express TH2-like cytokine ratios (IFN-γ < IL-4) in the luteal phase than in other phases. Similarly, sexually active women had significantly higher P, and higher P-E2 ratios, in the luteal phase than did abstinent women. The P-E2 ratio mediated menstrual variations in cytokine ratios in sexually active women. CONCLUSION(S) These results support the hypothesis that shifts in immune response across the menstrual cycle may reflect tradeoffs between reproduction and immunity. These findings point to the need for further research on the interaction between sexual behavior, the menstrual cycle, and immune response.
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Affiliation(s)
- Tierney K Lorenz
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Kinsey Institute for Research on Sex, Gender, and Reproduction, Indiana University, Bloomington, Indiana.
| | - Julia R Heiman
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Kinsey Institute for Research on Sex, Gender, and Reproduction, Indiana University, Bloomington, Indiana; Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana
| | - Gregory E Demas
- Center for Integrative Study for Animal Behavior, Indiana University, Bloomington, Indiana; Department of Biology, Indiana University, Bloomington, Indiana
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50
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Carlton ED, Demas GE. Body mass affects seasonal variation in sickness intensity in a seasonally breeding rodent. ACTA ACUST UNITED AC 2015; 218:1667-76. [PMID: 25852068 DOI: 10.1242/jeb.120576] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 04/01/2015] [Indexed: 01/20/2023]
Abstract
Species that display seasonal variation in sickness intensity show the most intense response in the season during which they have the highest body mass, suggesting that sickness intensity may be limited by an animal's energy stores. Siberian hamsters (Phodopus sungorus) display lower body masses and less intense sickness when housed in short, winter-like days as opposed to long, summer-like days. To determine whether reduced sickness intensity displayed by short-day hamsters is a product of seasonal changes in body mass, we food restricted long-day hamsters so that they exhibited body mass loss that mimicked the natural photoperiod-induced loss of body mass in short-day hamsters. We then experimentally induced sickness with lipopolysaccharide (LPS) and compared sickness responses among long-day food-restricted and long- and short-day ad libitum fed groups, predicting that long-day food-restricted hamsters would show sickness responses comparable to those of short-day ad libitum fed hamsters and attenuated in comparison to long-day ad libitum fed hamsters. We found that long-day food-restricted hamsters showed attenuated LPS-induced anorexia, loss of body mass and hypothermia compared with long-day ad libitum fed animals; however, anorexia remained elevated in long-day food-restricted animals compared with short-day ad libitum fed animals. Additionally, LPS-induced anhedonia and decreases in nest building were not influenced by body mass. Results of hormone assays suggest that cortisol levels could play a role in the attenuation of sickness in long-day food-restricted hamsters, indicating that future research should target the roles of glucocorticoids and natural variation in energy stores in seasonal sickness variation.
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Affiliation(s)
- Elizabeth D Carlton
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
| | - Gregory E Demas
- Department of Biology, Program in Neuroscience and Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN 47405, USA
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