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de Vries GJ, Forger NG. Sex differences in the brain: a whole body perspective. Biol Sex Differ 2015; 6:15. [PMID: 26279833 PMCID: PMC4536872 DOI: 10.1186/s13293-015-0032-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 07/28/2015] [Indexed: 12/29/2022] Open
Abstract
Most writing on sexual differentiation of the mammalian brain (including our own) considers just two organs: the gonads and the brain. This perspective, which leaves out all other body parts, misleads us in several ways. First, there is accumulating evidence that all organs are sexually differentiated, and that sex differences in peripheral organs affect the brain. We demonstrate this by reviewing examples involving sex differences in muscles, adipose tissue, the liver, immune system, gut, kidneys, bladder, and placenta that affect the nervous system and behavior. The second consequence of ignoring other organs when considering neural sex differences is that we are likely to miss the fact that some brain sex differences develop to compensate for differences in the internal environment (i.e., because male and female brains operate in different bodies, sex differences are required to make output/function more similar in the two sexes). We also consider evidence that sex differences in sensory systems cause male and female brains to perceive different information about the world; the two sexes are also perceived by the world differently and therefore exposed to differences in experience via treatment by others. Although the topic of sex differences in the brain is often seen as much more emotionally charged than studies of sex differences in other organs, the dichotomy is largely false. By putting the brain firmly back in the body, sex differences in the brain are predictable and can be more completely understood.
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Affiliation(s)
- Geert J. de Vries
- Neuroscience Institute, Georgia State University, P.O. Box 5030, Atlanta, GA 30302-5030 USA
| | - Nancy G. Forger
- Neuroscience Institute, Georgia State University, P.O. Box 5030, Atlanta, GA 30302-5030 USA
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Abstract
Spinal cord injury (SCI) results not only in motor and sensory deficits but also in autonomic dysfunctions. The disruption of connections between higher brain centers and the spinal cord, or the impaired autonomic nervous system itself, manifests a broad range of autonomic abnormalities. This includes compromised cardiovascular, respiratory, urinary, gastrointestinal, thermoregulatory, and sexual activities. These disabilities evoke potentially life-threatening symptoms that severely interfere with the daily living of those with SCI. In particular, high thoracic or cervical SCI often causes disordered hemodynamics due to deregulated sympathetic outflow. Episodic hypertension associated with autonomic dysreflexia develops as a result of massive sympathetic discharge often triggered by unpleasant visceral or sensory stimuli below the injury level. In the pelvic floor, bladder and urethral dysfunctions are classified according to upper motor neuron versus lower motor neuron injuries; this is dependent on the level of lesion. Most impairments of the lower urinary tract manifest in two interrelated complications: bladder storage and emptying. Inadequate or excessive detrusor and sphincter functions as well as detrusor-sphincter dyssynergia are examples of micturition abnormalities stemming from SCI. Gastrointestinal motility disorders in spinal cord injured-individuals are comprised of gastric dilation, delayed gastric emptying, and diminished propulsive transit along the entire gastrointestinal tract. As a critical consequence of SCI, neurogenic bowel dysfunction exhibits constipation and/or incontinence. Thus, it is essential to recognize neural mechanisms and pathophysiology underlying various complications of autonomic dysfunctions after SCI. This overview provides both vital information for better understanding these disorders and guides to pursue novel therapeutic approaches to alleviate secondary complications.
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Affiliation(s)
- Shaoping Hou
- Spinal Cord Research Center, Department of Neurobiology & Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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Newton BW. Walking a fine line: is it possible to remain an empathic physician and have a hardened heart? Front Hum Neurosci 2013; 7:233. [PMID: 23781181 PMCID: PMC3678078 DOI: 10.3389/fnhum.2013.00233] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/15/2013] [Indexed: 12/22/2022] Open
Abstract
Establishing an empathic physician-patient relationship is an essential physician skill. This chapter discusses the sexually dimorphic aspects of the neural components involved in affective and cognitive empathy, and examines why men and women medical students or physicians express different levels of empathy. Studies reveal levels of medical student affective or cognitive empathy can help reveal which medical specialty a student will enter. The data show students or physicians with higher empathy enter into specialties characterized by large amounts of patient contact and continuity of care; and individuals with lower levels of empathy desire specialties having little or no patient contact and little to no continuity of care. Burnout and stress can decrease the empathy physicians had when they first entered medical school to unacceptable levels. Conversely, having a too empathetic physician can let patient conditions and reactions interfere with the ability to provide effective care. By learning to blunt affective empathic responses, physicians establish a certain degree of empathic detachment with the patient in order to provide objective care. However, a physician must not become so detached and hardened that their conduct appears callous, because it is still important for physicians, especially those in specialties with a large amount of patient contact, to use empathic communication skills.
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Affiliation(s)
- Bruce W. Newton
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical SciencesLittle Rock, AR, USA
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Fuxjager MJ, Schultz JD, Barske J, Feng NY, Fusani L, Mirzatoni A, Day LB, Hau M, Schlinger BA. Spinal motor and sensory neurons are androgen targets in an acrobatic bird. Endocrinology 2012; 153:3780-91. [PMID: 22635677 PMCID: PMC5393326 DOI: 10.1210/en.2012-1313] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Sex steroids affect the motivation to court mates, but less is known about how they influence motor movements associated with courtship behavior. Steroidal control of motor function may be especially important for species in which courtship requires superior strength, stamina, and neuromuscular coordination. Here we use the golden-collared manakin (Manacus vitellinus) to examine whether the neuromuscular circuitry that controls motoric aspects of courtship activity is sensitive to androgens. Males of this tropical species attract mates by rapidly jumping among branches in a courtship arena and using their wings to produce loud wing snaps. Testosterone activates this display via the androgen receptor (AR), and past work reveals that manakins injected with radio-labeled T ((3)H-T) accumulate radioactivity in the spinal cord. Thus, we used quantitative PCR to measure AR, estrogen receptor-α (ER-α) subtype, and aromatase (AROM) mRNA in spinal cords of male and female manakins and zebra finches. Expression of AR, but not ER-α or aromatase, was higher throughout the manakin spinal cord compared with the zebra finch. Next, we tested whether AR-expressing skeletal muscles are innervated by motor and sensory neurons that also express AR. To do this, we backfilled spinal neurons by injecting fluorescent tracers into select AR-sensitive wing and leg muscles of wild caught male and female manakins. We then removed these spinal cords and measured AR expression with in situ hybridization. Both sexes showed abundant AR mRNA in the cervical and lumbosacral spinal enlargements as well as in dorsal root ganglia attached to these enlargements. Together our findings suggest that androgens act widely on peripheral motor and sensory circuits in golden-collared manakins to influence wing snapping displays.
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Affiliation(s)
- Matthew J Fuxjager
- Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California 90095-7239, USA
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Nation T, Buraundi S, Balic A, Southwell B, Newgreen D, Hutson J. Androgen and estrogen receptor expression in the spinal segments of the genitofemoral nerve during testicular descent. J Pediatr Surg 2011; 46:1539-43. [PMID: 21843721 DOI: 10.1016/j.jpedsurg.2010.11.035] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 11/21/2010] [Indexed: 11/25/2022]
Abstract
AIM During testicular descent (TD), the genitofemoral nerve (GFN) is masculinized by androgen. This study aimed to test whether androgen receptor (AR), estrogen receptor α (ERA), or estrogen receptor β (ERB) are expressed during TD in the GFN spinal segments and dorsal root ganglia (DRG) in normal and flutamide-treated rats. METHODS Time-mated Sprague-Dawley dams were injected with flutamide (75 mg/kg, subcutaneously (S/C) in sunflower oil) on embryonic (E) days 16 to 19. Embryonic and postnatal (P) male L1-2 spinal cord segments were collected (E16, E17, E19, P0, P2, and P4) in control and flutamide-treated groups (n = 5-10). Samples were fixed in 4% paraformaldehyde. Five-micrometer-thick sections were prepared immunohistochemically for AR, ERA, and ERB. RESULTS During TD, ERB was expressed in L1-2 DRG. Surprisingly, AR was not expressed in prenatal DRG, only after P2. There was no ERA expression. Flutamide had no effect on AR, ERB, or ERA expression in the L1-2 DRG during TD. CONCLUSION During the E window of androgen sensitivity, the GFN is not directly masculinized, with little AR expression and no change with flutamide over this period. Estrogen receptor β is expressed in the DRG during TD. However, its relevance is yet to be determined.
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Affiliation(s)
- Tamara Nation
- Douglas Stephens Surgical Research Laboratory, MCRI, Victoria, Australia
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Lenz KM, Sengelaub DR. Maternal care effects on SNB motoneuron development: the mediating role of sensory afferent distribution and activity. Dev Neurobiol 2009; 69:603-15. [PMID: 19472187 DOI: 10.1002/dneu.20729] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Maternal licking in rats affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Reduced maternal licking produces decreased motoneuron number, size, and dendritic length in the rostral portion of the adult SNB as well as deficits in adult male copulatory behavior. Previous research suggests that decreases in perineal tactile stimulation may be responsible for these effects. To determine whether the regional effects of maternal licking on SNB morphology are driven by sensory afferent innervation of the lumbosacral spinal cord, we used WGA-HRP to reconstruct the location of sensory afferent fibers from the perineal skin. We found that these fibers are caudally concentrated relative to the area of the SNB dendritic field, with the rostral dendritic arbor receiving little perineal afferent innervation. We also assessed Fos expression following perineal tactile stimulation to determine whether it increased local spinal cord activity in the SNB dendritic field. Sixty seconds of licking-like perineal stimulation produced a transient 115% increase in Fos expression in the area of the SNB dendritic field. This effect was driven by a significant increase in Fos in the caudal portion of the SNB dendritic field, matching the pattern of perineal afferent fiber labeling. Perineal tactile stimulation also produced significantly greater Fos expression in male pups than in female pups. Together, these results suggest that perineal sensory afferent activity mediates the effects of early maternal care on the masculinization of the SNB and resultant male copulatory behavior.
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Affiliation(s)
- Kathryn M Lenz
- Department of Psychological and Brain Sciences and Program in Neuroscience, Indiana University, Bloomington, IN 47405, USA
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Forger NG. The organizational hypothesis and final common pathways: Sexual differentiation of the spinal cord and peripheral nervous system. Horm Behav 2009; 55:605-10. [PMID: 19446077 PMCID: PMC2703449 DOI: 10.1016/j.yhbeh.2009.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 03/11/2009] [Accepted: 03/12/2009] [Indexed: 10/20/2022]
Abstract
In honor of the 50th anniversary of the "organizational hypothesis," this paper reviews work on sexual differentiation of the spinal cord and peripheral nervous system. Topics considered include the spinal nucleus of the bulbocavernosus, the ejaculation center, the cremaster nucleus, sensory and autonomic neurons, and pain. These relatively simple neural systems offer ample confirmation that early exposure to testicular hormones masculinizes the nervous system, including final common pathways. However, I also discuss findings that challenge, or at least stretch, the organizational hypothesis, with important implications for understanding sex differences throughout the nervous system.
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Affiliation(s)
- Nancy G Forger
- Department of Psychology and Center for Neuroendocrine Studies, University of Massachusetts, Amherst MA 01003, USA.
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8
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Luo H, Liu J, Kang D, Cui S. Ontogeny of estrogen receptor alpha, estrogen receptor beta and androgen receptor, and their co-localization with Islet-1 in the dorsal root ganglia of sheep fetuses during gestation. Histochem Cell Biol 2008; 129:525-33. [PMID: 18204852 DOI: 10.1007/s00418-008-0380-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2008] [Indexed: 02/02/2023]
Abstract
The aims of the present study were to detect the ontogeny of estrogen receptor (ERalpha and ERbeta) and androgen receptor (AR) expressions and their co-localization with Islet-1 in the developing dorsal root ganglia (DRG) of sheep fetuses by immunohistochemistry. From the single staining results, the ERalpha immunoreactivity (ERalpha-ir), ERbeta immunoreactivity (ERbeta-ir) and AR immunoreactivity (AR-ir) was first detected at days 90, 120 and 90 of gestation, respectively. From days 90 to 120, ERalpha and AR were consistently detected in the nuclei of DRG neurons and the relative percentage (approximately 60%) of ERalpha-ir or AR-ir cells did not change significantly. Moreover, there was no change in ERalpha expression, while a dramatic loss of AR expression was observed at birth. From day 120 of gestation to birth, very few neurons (approximately 8%) showed nuclear ERbeta immunoreactivity. The dual staining results showed that Islet-1 was co-localized with ERalpha, ERbeta or AR in the nuclei of DRG neurons with various frequencies, and over 70% ERalpha-ir, ERbeta-ir or AR-ir cells contained Islet-1. These results imply that ERs, AR and Islet-1 may be important in regulating the differentiation and functional maintenance of some phenotypes of DRG neurons after mid-gestation in the sheep fetus.
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Affiliation(s)
- Haoshu Luo
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100094, People's Republic of China
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9
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Newton BW, Phan DC. Androgens regulate the sexually dimorphic production of co-contained galanin and cholecystokinin in lumbar laminae VII and X neurons. Brain Res 2006; 1099:88-96. [PMID: 16764834 DOI: 10.1016/j.brainres.2006.04.106] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Revised: 04/24/2006] [Accepted: 04/28/2006] [Indexed: 12/29/2022]
Abstract
A population of rat lumbar laminae VII and X putative spinothalamic (STT) neurons that co-contain cholecystokinin-8 (CCK) and galanin (GAL) are sexually dimorphic. Males have a significantly greater number of these neurons, as well as having greater optical densities for both neuropeptides than females. Optical densities for GAL and CCK immunoreactivities in these lumbar neurons in rats that have the testicular feminization mutation (Tfm) are not significantly different from females; however, the number of these lumbar neurons in Tfm rats is significantly smaller than in females. These data suggest that androgens, as well as functional androgen receptors (that Tfm rats lack), are necessary for the establishment of these sexual dimorphisms. Functionally, these CCK- and GAL-containing neurons in the deep lumbar laminae may contribute to the establishment of known sex differences in the affective component of somatic and visceral nociception, as well as the sexually dimorphic nature of some pelvic diseases, e.g., irritable bowel syndrome or cystitis.
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Affiliation(s)
- Bruce W Newton
- Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, 72205, USA.
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10
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Lenz KM, Sengelaub DR. Maternal licking influences dendritic development of motoneurons in a sexually dimorphic neuromuscular system. Brain Res 2006; 1092:87-99. [PMID: 16674931 DOI: 10.1016/j.brainres.2006.03.070] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 03/21/2006] [Accepted: 03/22/2006] [Indexed: 12/29/2022]
Abstract
Maternal licking of pups' perineal regions affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus in the lumbar spinal cord that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneuron number, with reductions in licking resulting in fewer motoneurons. Reduced maternal licking also has functional consequences in adulthood, resulting in increased latency to ejaculation and postejaculatory intromission and longer interintromission intervals. In this experiment, we assessed the potential effect of maternal licking on the development of SNB dendritic morphology. To reduce maternal licking, dams were treated with intranasal application of zinc sulfate during the first two postnatal weeks, which interferes with their ability to detect the pup odors that drive the licking behavior. At either postnatal day (P) 28 (when SNB dendritic length is normally maximal) or P49 (when SNB dendritic morphology is normally mature), SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP, and dendritic arbor was reconstructed in three dimensions. At P28, the dendritic arbor of reduced maternal licking pups was not different from controls; however at P49, reduced licking pups showed a 23% reduction in dendritic arbor in the SNB, an effect that was especially pronounced in the rostral end of the nucleus, where reductions reached 48%. These results suggest that reductions in perineal stimulation provided by maternal licking could affect adult male copulatory behavior via alterations in SNB motoneuron morphology, and thus support maternal licking as an important factor in normal neural and behavioral development.
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Affiliation(s)
- Kathryn M Lenz
- Department of Psychological and Brain Sciences and Program in Neuroscience, 1101 E. 10th Street, Indiana University, Bloomington, IN 47405, USA
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11
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Huerta-Ocampo I, Mena F, Barrios F, Martínez G, González L, Larriva-Sahd J. Perinatal exposure to androgen suppresses sexual dimorphism in nerve trunk diameter, axon number, and fiber size spectrum: a quantitative ultrastructural study of the adult rat mammary nerve. Brain Res 2005; 1060:179-83. [PMID: 16226232 DOI: 10.1016/j.brainres.2005.07.051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 07/22/2005] [Accepted: 07/25/2005] [Indexed: 02/05/2023]
Abstract
The adult mammary nerves (MNs) from female, male, and testosterone-androgenized female rats were studied by light and electron microscopy. The female MNs trunk has twice the diameter of that of the male. Morphometry showed a significantly more myelinated (307 +/- 6) and unmyelinated axons (1654 +/- 10) in the female MN than the male MN (278 +/- 6 and 1373 +/- 28, respectively). Perinatal exposure of the female to testosterone significantly reduced the number of both axon types in the MN in adulthood (244 +/- 6 myelinated and 1300 +/- 32, unmyelinated). Another sexual dimorphism is a distinct group of large (>7.0 microm in diameter) myelinated axons known to conduct sensory information (i.e., touch and vibration). Because the male and the perinatally-androgenized female MNs lack these fibers, it is concluded that gonadal sex hormones may promote the differentiation of specific sets of axons committed to transmission of sensory cues relevant to reproduction.
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Affiliation(s)
- Icnelia Huerta-Ocampo
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus UNAM-UAQ, Apartado Postal 1-1141, Zona Centro, Querétaro, CP 76001 Qro., Mexico
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12
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Colbert NKW, Pelletier NC, Cote JM, Concannon JB, Jurdak NA, Minott SB, Markowski VP. Perinatal exposure to low levels of the environmental antiandrogen vinclozolin alters sex-differentiated social play and sexual behaviors in the rat. ENVIRONMENTAL HEALTH PERSPECTIVES 2005; 113:700-7. [PMID: 15929892 PMCID: PMC1257594 DOI: 10.1289/ehp.7509] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
In this study we examined the effects of exposure to the antiandrogenic fungicide vinclozolin (Vz) on the development of two sex-differentiated behaviors that are organized by the perinatal actions of androgens. Pregnant Long-Evans rats were administered a daily oral dose of 0, 1.5, 3, 6, or 12 mg/kg Vz from the 14th day of gestation through postnatal day (PND)3. The social play behavior of juvenile offspring was examined on PND22 and again on PND34 during play sessions with a same-sex littermate. After they reached adulthood, the male offspring were examined with the ex copula penile reflex procedure to assess erectile function. Vz did not produce any gross maternal or neonatal toxicity, nor did it reduce the anogenital distance in male pups. We observed no effects of Vz on play behavior on PND22. However, the 12-mg/kg Vz dose significantly increased play behavior in the male offspring on PND34 compared with controls. The most dramatic increases were seen with the nape contact and pounce behavior components of play. The Vz effect was more pronounced in male than in female offspring. As adults, male offspring showed a significant reduction of erections at all dose levels during the ex copula penile reflex tests. The 12-mg/kg dose was also associated with an increase in seminal emissions. These effects demonstrate that perinatal Vz disrupts the development of androgen-mediated behavioral functions at exposure levels that do not produce obvious structural changes or weight reductions in androgen-sensitive reproductive organs.
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Affiliation(s)
- Nathan K W Colbert
- Maine Center for Toxicology and Environmental Health, University of Southern Maine, Portland, Maine 04104-9300, USA
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Liu J, Chen D, Goldstein RS, Cui S. Effects of male and female sex steroids on the development of normal and the transient Froriep's dorsal root ganglia of the chick embryo. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 155:14-25. [PMID: 15763271 DOI: 10.1016/j.devbrainres.2004.12.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2004] [Revised: 12/08/2004] [Accepted: 12/09/2004] [Indexed: 11/16/2022]
Abstract
Sex steroids can influence developmental processes and support the survival of neurons in the embryonic central nervous system. Recent studies have shown that estrogen receptors are also expressed in the peripheral nervous system, in the dorsal root ganglia (DRG) of chick embryos. However, no studies have examined the effects of sex steroids on development of embryonic DRG. In the present study, 0.2 microg, 1.0 microg, 5.0 microg 10 microg, 20 microg, 25 microg, and 40 microg doses of testosterone or estradiol were delivered to chick embryos at Hamburger and Hamilton stage 18 (E3). The actions of these doses of sex steroids on the development of the C5DRG (fifth cervical ganglion, a "normal" DRG) and C2DRG (a transient ganglion known as a "Froriep's DRG") were then evaluated by quantifying ganglionic volumes, cell number, proliferation, and apoptosis after 1 day of growth to stage 23. We found that both testosterone and estradiol promoted proliferation of cells in both normal DRG and the Froriep's ganglia. By contrast, estradiol significantly increased the number of apoptotic cells, while testosterone strongly inhibited apoptosis. These actions of sex steroids on DRG development were dose-dependent, and C5DRG and C2DRG showed different sensitivities to the applied sex steroids. In addition, the present results demonstrated that specific ER and AR inhibitors (tamoxifen and flutamide) did not influence the effects of 5 microg E2 and 5 microg T on C2 and C5DRG significantly. These results demonstrate that male and female sex steroids can modulate DRG development through an epigenetic mechanism, as had been shown for the central nervous system.
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Affiliation(s)
- Jiali Liu
- College of Biological Sciences, China Agricultural University, Beijing, 100094, PR China
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Foster AM, Sengelaub DR. Bilateral organization of unilaterally generated activity in lumbar spinal motoneurons of the rat. Brain Res 2004; 1009:98-109. [PMID: 15120587 DOI: 10.1016/j.brainres.2004.02.047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/28/2004] [Indexed: 02/08/2023]
Abstract
The spinal nucleus of the bulbocavernosus (SNB) is a medially located, bilaterally organized sexually dimorphic motor nucleus in the lumbar spinal cord of the male rat. To begin to assess the potential functional significance of this bilateral organization, we recorded ipsi- and contralateral SNB motor nerve activity following unilateral spinal stimulation and examined the timing, pattern, and recruitment of population motoneuron activity. A possible mechanism for bilateral communication, gap junctional intercellular communication, was also investigated because dye coupling experiments indicate an extensive syncytium in which SNB motoneurons are coupled with each other and neighboring interneurons. An in vivo peripheral nerve recording paradigm was used: a bipolar stimulating electrode was placed on dorsal root L6, and bipolar recording electrodes were placed bilaterally on the SNB motor nerves. All processes were severed distal to electrode placement to isolate the central preparation; recruitment curves of motoneuronal activity were then generated. Amplitude of peak to peak recruitment was greater in the contralateral motor nerve than in the ipsilateral nerve. Response latency, Fourier transform and spike counts showed no evidence of ipsi/contralateral asymmetry. Recruitment was attenuated both ipsi- and contralaterally after pharmacological gap junction blockade, but antidromic stimulation could not drive activity in contralateral motor axons. These results indicate that unilateral input to the SNB may be differentially modulated to produce functionally distinct output in the two separate halves of the nucleus. We also discuss the potential modulatory role of gap junctions in the activity of the SNB.
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Affiliation(s)
- Allison Marie Foster
- Department of Psychology, Program in Neural Science, Indiana University, Bloomington, IN 47405, USA
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15
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Gans S, Erskine MS. Effects of neonatal testosterone treatment on pacing behaviors and development of a conditioned place preference. Horm Behav 2003; 44:354-64. [PMID: 14613730 DOI: 10.1016/s0018-506x(03)00157-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Two experiments assessed the effects of neonatal testosterone treatment on paced mating behavior and conditioned place preference in female rats. In both experiments, females received s.c. injections of 5.0 microg testosterone propionate or oil vehicle at three days postpartum. As adults, females were ovariectomized and given s.c. injections of 10 microg estradiol benzoate and 500 microg progesterone, 48 and 4 h before mating, respectively. In Experiment 1, TP- and Oil-treated females exhibited similar high levels of lordosis responsiveness, but TP-treated females showed increased intervals between mounts and between intromissions in paced and non-paced mating conditions compared to control females. The effect was particularly pronounced during paced mating, when contact return latencies were increased approximately 2-fold by TP treatment. TP-treated females showed exaggerated pacing behavior, showing significantly greater return latencies after intromissions than Oil-treated females. In Experiment 2, TP- and Oil-treated groups were tested in a conditioned place preference paradigm to determine if the behavioral changes observed in Experiment 1 were in part a result of changes in the perceived reward produced by paced mating. TP treated and control females developed equivalent preferences for places associated with paced but not non-paced mating, indicating that neonatal TP treatment at this dosage does not disrupt or enhance the conditioned place preference induced by paced mating. The results of the two experiments demonstrate that neonatal TP treatment alters the display of pacing behavior but not the reward state induced by paced mating, and suggest that TP affects neural substrates involved in performance of paced mating without effects on those controlling lordosis or place preference conditioning.
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Affiliation(s)
- Susan Gans
- Department of Biology, Boston University, Boston, MA 02215, USA
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Newton RA, Bingham S, Davey PD, Medhurst AD, Piercy V, Raval P, Parsons AA, Sanger GJ, Case CP, Lawson SN. Identification of differentially expressed genes in dorsal root ganglia following partial sciatic nerve injury. Neuroscience 2000; 95:1111-20. [PMID: 10682718 DOI: 10.1016/s0306-4522(99)00515-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Partial sciatic nerve injury, a model of neuropathic pain, elicits a variety of neurochemical, electrophysiological and neuroanatomical changes in primary sensory neurons. We have used the technique of messenger RNA differential display to identify genes with altered expression in these neurons which may contribute to the development of aberrant sensation following such peripheral nerve damage. This approach identified 14 distinct complementary DNA clones, representing transcripts with increased ipsilateral expression in L4/5 dorsal root ganglia, two weeks after unilateral partial ligation of the rat sciatic nerve. Both Zucker diabetic fatty rats and their lean counterparts were used in this study but none of the transcripts identified showed an induction that was confined to one of the two groups. The majority of the clones did not show significant sequence similarity to previously reported genes and therefore may represent novel messenger RNA sequences or, alternatively, unknown regions of partially characterised messenger RNAs. Two of the clones represented transcripts for the known proteins muscle LIM protein and acidic epididymal glycoprotein, neither of which had previously been associated with expression in the nervous system. Reverse transcriptase-polymerase chain reaction analysis and in situ hybridization confirmed that the messenger RNA expression of both muscle LIM protein and acidic epididymal glycoprotein was induced in an ipsilateral-specific manner. Their localisations, examined with in situ hybridization in L5 dorsal root ganglia, were limited in each case to a sub-population of neuronal profiles. Those neuronal profiles that demonstrated muscle LIM protein hybridization were distributed across the profile size range, whereas the distribution of acidic epididymal glycoprotein-positive profiles appeared to be skewed towards smaller profiles. The induction of muscle LIM protein and acidic epididymal glycoprotein in dorsal root ganglia may play an important functional role in the adaptive response of primary sensory neurons following partial sciatic nerve injury.
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Affiliation(s)
- R A Newton
- Department of Physiology, The School of Medical Sciences, Bristol, UK
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17
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Keast JR. The autonomic nerve supply of male sex organs--an important target of circulating androgens. Behav Brain Res 1999; 105:81-92. [PMID: 10553692 DOI: 10.1016/s0166-4328(99)00084-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The autonomic nervous system plays a critical role in the regulation of smooth muscle contraction, exocrine secretion and blood flow in the male reproductive organs. Many of the autonomic neurons that supply these targets lie in the pelvic ganglia, which contain both sympathetic and parasympathetic ganglion cells. In rats, removal of circulating androgens by castration before or after puberty has profound effects on the structure, chemistry and function of particular classes of pelvic autonomic neurons. While most of these effects occur in reproductive pathways, some bladder- or bowel-projecting neurons also exhibit androgen-sensitivity. Our studies on these ganglion cells and their spinal preganglionic inputs show that testosterone (or a metabolite) has potent actions both before and after puberty and can be considered essential for the normal maturation and maintenance of some pelvic autonomic reflex pathways. Androgen receptors are distributed widely throughout various components of these circuits, suggesting that testosterone may have direct effects on neuronal gene expression. Together, the studies show that in addition to powerful effects on some central neurons controlling reproductive behaviour, testosterone has similarly important effects on peripheral neurons that trigger and complete copulatory reflexes.
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Affiliation(s)
- J R Keast
- Department of Physiology and Pharmacology, University of Queensland, Australia.
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18
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Taleghany N, Sarajari S, DonCarlos L, Gollapudi L, Oblinger M. Differential expression of estrogen receptor alpha and beta in rat dorsal root ganglion neurons. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19990901)57:5<603::aid-jnr3>3.0.co;2-r] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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19
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Keast JR, Gleeson RJ. Androgen receptor immunoreactivity is present in primary sensory neurons of male rats. Neuroreport 1998; 9:4137-40. [PMID: 9926862 DOI: 10.1097/00001756-199812210-00025] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We have examined the distribution of androgen receptor (AR) immunoreactivity in L6 and S1 dorsal root ganglia of male rats in order to determine whether the sensory component of reflex circuits is likely to be androgen-sensitive. Nuclear AR immunoreactivity was present in almost half of the neurons, but was decreased markedly by castration; after castration nuclear staining was absent and a few neurons showed dim cytoplasmic staining. Of the neurons possessing AR, half also contained calcitonin gene-related peptide (CGRP); in turn, > 80% of CGRP neurons contained AR. AR staining was present in both large and small CGRP neurons. This study shows that testosterone is likely to influence many sensory neurons and may therefore play an important role in modulating visceral and somatic reflexes.
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Affiliation(s)
- J R Keast
- Department of Physiology and Pharmacology, University of Queensland, St Lucia, Australia
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20
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Burek MJ, Nordeen KW, Nordeen EJ. Sexually dimorphic neuron addition to an avian song-control region is not accounted for by sex differences in cell death. ACTA ACUST UNITED AC 1997. [DOI: 10.1002/(sici)1097-4695(199707)33:1<61::aid-neu6>3.0.co;2-b] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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21
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Streichert LC, Pierce JT, Nelson JA, Weeks JC. Steroid hormones act directly to trigger segment-specific programmed cell death of identified motoneurons in vitro. Dev Biol 1997; 183:95-107. [PMID: 9119119 DOI: 10.1006/dbio.1996.8467] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In larvae of the hawkmoth, Manduca sexta, accessory planta retractor (APR) motoneurons undergo a segment-specific pattern of programmed cell death at pupation. APR death is triggered hormonally by the prepupal peak of the ecdysteroid, 20-hydroxyecdysone (20-HE). Previous studies found no evidence that cellular interactions regulate the segmental pattern of APR death in vivo. To test the hypothesis that 20-HE acts directly on APRs to trigger a cell-autonomous, segment-specific pattern of death, APRs were labeled with the fluorescent dyes DiI or DiA, removed from the nervous system before the prepupal peak, and placed in low-density cell culture. Physiological levels of 20-HE triggered the same segment-specific pattern of APR death in vitro as seen in vivo, both in cultures containing a single APR and in cultures containing two APRs removed from the same donor animal. The presence or absence of contact with other cells did not influence the APRs' responses to 20-HE. The death of APRs in culture was characterized by fragmentation or rounding up of the cell body and fragmentation of the neurites. These findings suggest that intrinsic segmental identity regulates whether these motoneurons live or die when exposed to a steroid hormone during development.
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Affiliation(s)
- L C Streichert
- Institute of Neuroscience, University of Oregon, Eugene 97403-1254, USA
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22
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Moore CL, Dou H, Juraska JM. Number, size, and regional distribution of motor neurons in the dorsolateral and retrodorsolateral nuclei as a function of sex and neonatal stimulation. Dev Psychobiol 1996; 29:303-13. [PMID: 8732805 DOI: 10.1002/(sici)1098-2302(199605)29:4<303::aid-dev1>3.0.co;2-u] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Motor neurons were measured in the retrodorsolateral nucleus (RDLN) and the dorsolateral nucleus (DLN) of adult male and female rats that were reared with normal or reduced levels of maternal anogenital stimulation. In contrast with findings for the spinal nucleus of the bulbocavernosus, which is located in the same spinal segments, reduced stimulation had no effect on neuron number in either nucleus. However, several regional and sex differences were observed. Rostrally located neurons were larger in both the RDLN and the DLN; these location effects were greater in females. There was no sex difference in RDLN neuron size, but DLN neurons were larger in females, particularly in the rostral region. Females had significantly more cells in the RDLN, a nucleus previously considered nondimorphic, whereas males had more DLN neurons. Both regional and sex differences may reflect local differences in trophic factors from targets or afferents.
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Affiliation(s)
- C L Moore
- Department of Psychology, University of Massachusetts, Boston 02125, USA
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23
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Burek MJ, Nordeen KW, Nordeen EJ. Initial sex differences in neuron growth and survival within an avian song nucleus develop in the absence of afferent input. JOURNAL OF NEUROBIOLOGY 1995; 27:85-96. [PMID: 7643078 DOI: 10.1002/neu.480270109] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Only male zebra finches (Poephila guttata) sing, and nuclei implicated in song behavior exhibit marked sex differences in neuron number. In the robust nucleus of the anterior neostriatum (RA), these sex differences develop because more neurons die in young females than in males. However, it is not known whether the sexually dimorphic survival of RA neurons is a primary event in sexual differentiation or a secondary response to sex differences in the number of cells interacting trophically with RA neurons. In particular, since sexual differentiation of the RA parallels the development of dimorphisms in the numbers of neurons providing afferent input from the lateral magnocellular nucleus of the anterior neostriatum (IMAN) and the high vocal center (HVC), it has been hypothesized that sex differences in the size of these afferent populations trigger differential RA neuron survival and growth. To test this hypothesis, we lesioned either the IMAN or both the IMAN and HVC unilaterally in 12-day-old male and female zebra finches. Subsequently, RA cell death and RA neuron number and size were measured. Unilateral IMAN lesions increased cell death and decreased neuron number and size within the ipsilateral RA of both sexes. However, even in the IMAN-lesioned hemisphere, these effects were less pronounced in males than in females, so that by day 25 the volume, number, and size of neurons were sexually dimorphic in both the contralateral and ipsilateral RA. Similarly, the absence of both IMAN and HVC afferents did not prevent the emergence of sex differences in the number and size of RA neurons by 25 days posthatching. We conclude that these sex differences within the RA are not a secondary response to dimorphisms in the numbers of IMAN or HVC neurons providing afferent input.
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Affiliation(s)
- M J Burek
- Interdepartmental Neuroscience Program, University of Rochester, New York 14627, USA
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Affiliation(s)
- M D Madeira
- Department of Anatomy, Porto Medical School, Portugal
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25
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Maternal Contributions to Mammalian Reproductive Development and the Divergence of Males and Females. ADVANCES IN THE STUDY OF BEHAVIOR 1995. [DOI: 10.1016/s0065-3454(08)60392-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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