Behavioral and epigenetic consequences of oxytocin treatment at birth

Oxytocin is used in approximately half of all births in the United States during labor induction and/or augmentation. However, the effects of maternal oxytocin administration on offspring development have not been fully characterized. Here, we used the socially monogamous prairie vole to examine the hypothesis that oxytocin exposure at birth can have long-term developmental consequences. Maternally administered oxytocin increased methylation of the oxytocin receptor (Oxtr) in the fetal brain. As adults, oxytocin-exposed voles were more gregarious, with increased alloparental caregiving toward pups and increased close social contact with other adults. Cross-fostering indicated that these effects were the result of direct action on the offspring, rather than indirect effects via postnatal changes in maternal behavior. Male oxytocin-exposed offspring had increased oxytocin receptor density and expression in the brain as adults. These results show that long-term effects of perinatal oxytocin may be mediated by an epigenetic mechanism.

Peripheral oxytocin and vasopressin modulates regional brain activity differently in men and women with schizophrenia

BACKGROUND

Oxytocin (OT) and arginine vasopressin (AVP) exert sexually dimorphic effects on cognition and emotion processing. Abnormalities in these hormones are observed in schizophrenia and may contribute to multiple established sex differences associated with the disorder. Here we examined sex-dependent hormone associations with resting brain activity and their clinical associations in schizophrenia patients.

METHODS

OT and AVP serum concentrations were assayed in 35 individuals with schizophrenia (23 men) and 60 controls (24 men) from the Chicago BSNIP study site. Regional cerebral function was assessed with resting state fMRI by measuring the amplitude of low-frequency fluctuations (ALFF) which are believed to reflect intrinsic spontaneous neuronal activity.

RESULTS

In female patients, lower OT levels were associated with lower ALFF in frontal and cerebellar cortices (p's < 0.05) and in female controls AVP levels were inversely associated with ALFF in the frontal cortex (p = 0.01). In male patients, lower OT levels were associated with lower ALFF in the posterior cingulate and lower AVP levels were associated with lower ALFF in frontal cortex (p's < 0.05). In male controls, lower OT levels were associated with lower ALFF in frontal cortex and higher ALFF in the thalamus (p's < 0.05). There were some inverse ALFF-behavior associations in patients.

CONCLUSIONS

Alterations in peripheral hormone levels are associated with resting brain physiology in a sex-dependent manner in schizophrenia. These effects may contribute to sex differences in psychiatric symptom severity and course of illness in schizophrenia.

Associations between oxytocin receptor gene (OXTR) methylation, plasma oxytocin, and attachment across adulthood

The neuropeptide oxytocin (OT) has been implicated in a wide range of affiliative processes. OT exerts its functions via OT receptors, which are encoded by the oxytocin receptor gene (OXTR). Epigenetic modification of OXTR through the process of DNA methylation has been associated with individual differences in behavioral phenotypes. Specifically, lower levels of OXTR methylation have been linked to better social and affective functioning. However, research on epigenetic mechanisms of OXTR is scarce in non-clinical populations, and even less is known about epigenetic variability across adulthood. The present study assessed methylation levels at OXTR CpG site -934 and plasma OT levels in 22 young (20-31 years, M = 23.6) and 34 older (63-80 years, M = 71.4) participants. Lower levels of OXTR methylation and higher plasma OT levels were associated with less self-reported attachment anxiety in young but not older participants, with largely independent contributions of OXTR methylation and plasma OT levels. In contrast, in the overall sample, lower levels of OXTR methylation were associated with higher self-reported attachment avoidance. Age analysis suggested that these results were largely driven by young adults. Plasma OT levels were unrelated to attachment avoidance. Taken together, these findings support the emerging notion in the literature that epigenetic properties of OXTR, in addition to endogenous OT levels, are related to adult attachment. Further, the age effects observed in the associations between OXTR methylation, plasma OT, and adult attachment emphasize the importance of adopting a developmental perspective when studying properties of the OT system and their relation to affiliative processes. Findings contribute to growing evidence suggesting that epigenetic modification of genes regulating OT pathways and endogenous OT levels are associated with the way people form and maintain intimate social relationships.

Sex differences in associations of arginine vasopressin and oxytocin with resting-state functional brain connectivity

Oxytocin (OT) and arginine vasopressin (AVP) exert robust and sexually dimorphic influences on cognition and emotion. How these hormones regulate relevant functional brain systems is not well understood. OT and AVP serum concentrations were assayed in 60 healthy individuals (36 women). Brain functional networks assessed with resting-state functional magnetic resonance imaging (rs-fMRI) were constructed with graph theory-based approaches that characterize brain networks as connected nodes. Sex differences were demonstrated in rs-fMRI. Men showed higher nodal degree (connectedness) and efficiency (information propagation capacity) in left inferior frontal gyrus (IFG) and bilateral superior temporal gyrus (STG) and higher nodal degree in left rolandic operculum. Women showed higher nodal betweenness (being part of paths between nodes) in right putamen and left inferior parietal gyrus (IPG). Higher hormone levels were associated with less intrinsic connectivity. In men, higher AVP was associated with lower nodal degree and efficiency in left IFG (pars orbitalis) and left STG and less efficiency in left IFG (pars triangularis). In women, higher AVP was associated with lower betweenness in left IPG, and higher OT was associated with lower nodal degree in left IFG (pars orbitalis). Hormones differentially correlate with brain networks that are important for emotion processing and cognition in men and women. AVP in men and OT in women may regulate orbital frontal cortex connectivity, which is important in emotion processing. Hormone associations with STG and pars triangularis in men and parietal cortex in women may account for well-established sex differences in verbal and visuospatial abilities, respectively. © 2016 Wiley Periodicals, Inc.

The Role of Endogenous Oxytocin in Anxiolysis: Structural and Functional Correlates

BACKGROUND

Oxytocin is anxiolytic, and administration of synthetic oxytocin in humans reduces amygdala reactivity to negative stimuli. However, it is unknown whether endogenous oxytocin levels-which are heritable and stable across time-attenuate anxiety via similar mechanisms.

METHODS

In this study, we used plasma assays and structural and functional neuroimaging to examine potential anxiolytic effects of endogenous oxytocin in 73 participants.

RESULTS

We found that higher endogenous oxytocin levels are associated with reduced central amygdala volume and blood oxygen level-dependent activity in response to aversive stimuli. In contrast to previous reports, we found that oxytocin was not related to patterns of functional connectivity between the amygdala and other brain regions.

CONCLUSIONS

Together, our results underscore the importance of considering individual differences in participants' endogenous oxytocin with respect to anxiety-related neural activity and neuromorphology.

Effects of sex, menstrual cycle phase, and endogenous hormones on cognition in schizophrenia

BACKGROUND

In women with schizophrenia, cognition has been shown to be enhanced following administration of hormone therapy or oxytocin. We examined how natural hormonal changes across the menstrual cycle influence cognition in women with schizophrenia. We hypothesized that female patients would perform worse on "female-dominant" tasks (verbal memory/fluency) and better on "male-dominant" tasks (visuospatial) during the early follicular phase (low estradiol and progesterone) compared to midluteal phase (high estradiol and progesterone) in relation to estradiol but not progesterone.

METHODS

Fifty-four women (23 with schizophrenia) completed cognitive assessments and provided blood for sex steroid assays and oxytocin at early follicular (days 2-4) and midluteal (days 20-22) phases. Men were included to verify the expected pattern of sex differences on cognitive tests.

RESULTS

Expected sex differences were observed on "female-dominant" and "male-dominant" tasks (p<0.001), but the magnitude of those differences did not differ between patients and controls (p=0.44). Cognitive performance did not change across the menstrual cycle on "female-dominant" or "male-dominant" tasks in either group. Estradiol and progesterone levels were unrelated to cognitive performance. Oxytocin levels did not change across the menstrual cycle but were positively related to performance on "female-dominant" tasks in female patients only (p<0.05).

CONCLUSIONS

Sex differences in cognitive function are preserved in schizophrenia. Oxytocin levels do not change across the cycle, but relate to enhanced performance on female dominant tests in women. Physiological levels of oxytocin may thus have a more powerful benefit in some cognitive domains than estrogens in schizophrenia.

Plasma oxytocin explains individual differences in neural substrates of social perception

The neuropeptide oxytocin plays a critical role in social cognition and behavior. A number of studies using intranasal administration have demonstrated that oxytocin improves social perception. However, little is known about the relationship between individual differences in endogenous levels of oxytocin and social cognition. In the current study, we assessed the relationship between endogenous oxytocin and brain activity during an animacy perception paradigm. Thirty-seven male participants underwent scanning and provided a blood sample for oxytocin analysis. In line with previous research, perception of animacy was associated with activations in superior temporal sulcus, inferior frontal gyrus, and medial prefrontal cortex (mPFC). Notably, participants’ levels of plasma oxytocin robustly predicted activation in areas critical for social cognitive processes, such that higher oxytocin levels were related to increased activity in dorsal mPFC, ventral mPFC, dorsolateral PFC, superior temporal gyrus, and temporoparietal junction (TPJ), suggesting differential processing of social stimuli. Together these results show that stable variations in endogenous oxytocin levels explain individual differences in social perception.

Changes in social functioning and circulating oxytocin and vasopressin following the migration to a new country

Prior studies have reported associations between plasma oxytocin and vasopressin and markers of social functioning. However, because most human studies have used cross-sectional designs, it is unclear whether plasma oxytocin and vasopressin influences social functioning or whether social functioning modulates the production and peripheral release of these peptides. In order to address this question, we followed individuals who experienced major changes in social functioning subsequent to the migration to a new country. In this study, 59 new international students were recruited shortly after arrival in the host country and reassessed 2 and 5 months later. At each assessment participants provided information on their current social functioning and blood samples for oxytocin and vasopressin analysis. Results indicated that changes in social functioning were not related to changes in plasma oxytocin. Instead, baseline oxytocin predicted changes in social relationship satisfaction, social support, and loneliness over time. In contrast, plasma vasopressin changed as a function of social integration. Baseline vasopressin was not related to changes in social functioning over time. These results emphasize the different roles of plasma oxytocin and vasopressin in responses to changes in social functioning in humans.

Reduced levels of vasopressin and reduced behavioral modulation of oxytocin in psychotic disorders

Oxytocin (OT) and arginine vasopressin (AVP) exert robust influence on social affiliation and specific cognitive processes in healthy individuals. Abnormalities in these neuroendocrine systems have been observed in psychotic disorders, but their relation to impairments in behavioral domains that these endocrines modulate is not well understood. We compared abnormalities of OT and AVP serum concentrations in probands with schizophrenia (n = 57), schizoaffective disorder (n = 34), and psychotic bipolar disorder (n = 75); their first-degree relatives without a history of psychosis (n = 61, 43, 91, respectively); and healthy controls (n = 66) and examined their association with emotion processing and cognition. AVP levels were lower in schizophrenia (P = .002) and bipolar probands (P = .03) and in relatives of schizophrenia probands (P = .002) compared with controls. OT levels did not differ between groups. Familiality estimates were robust for OT (h(2) = 0.79, P = 3.97e-15) and AVP (h(2) = 0.78, P = 3.93e-11). Higher levels of OT were associated with better emotion recognition (β = 0.40, P < .001) and general neuropsychological function (β = 0.26, P = .04) in healthy controls as expected but not in any proband or relative group. In schizophrenia, higher OT levels were related to greater positive symptom severity. The dissociation of OT levels and behavioral function in all proband and relative groups suggests that risk and illness factors associated with psychotic disorders are not related to reduced OT levels but to a disruption in the ability of physiological levels of OT to modulate social cognition and neuropsychological function. Decreased AVP levels may be a marker of biological vulnerability in schizophrenia because alterations were seen in probands and relatives, and familiality was high.

Oxytocin in pregnancy and the postpartum: relations to labor and its management

The purpose of this study was to examine variations in endogenous oxytocin levels in pregnancy and postpartum state. We also explored the associations between delivery variables and oxytocin levels. A final sample of 272 mothers in their first trimester of pregnancy was included for the study. Blood samples were drawn during the first trimester and third trimester of pregnancy and at 8 weeks postpartum. Socio-demographic data were collected at each time point and medical files were consulted for delivery details. In most women, levels of circulating oxytocin increased from the first to third trimester of pregnancy followed by a decrease in the postpartum period. Oxytocin levels varied considerably between individuals, ranging from 50 pg/mL to over 2000 pg/mL. Parity was the main predictor of oxytocin levels in the third trimester of pregnancy and of oxytocin level changes from the first to the third trimester of pregnancy. Oxytocin levels in the third trimester of pregnancy predicted a self-reported negative labor experience and increased the chances of having an epidural. Intrapartum exogenous oxytocin was positively associated with levels of oxytocin during the postpartum period. Our exploratory results suggest that circulating oxytocin levels during the third trimester of pregnancy may predict the type of labor a woman will experience. More importantly, the quantity of intrapartum exogenous oxytocin administered during labor predicted plasma oxytocin levels 2 months postpartum, suggesting a possible long-term effect of this routine intervention, the consequences of which are largely unknown.

Autonomic substrates of the response to pups in male prairie voles

Caregiving by nonparents (alloparenting) and fathers is a defining aspect of human social behavior, yet this phenomenon is rare among mammals. Male prairie voles (Microtus ochrogaster) spontaneously exhibit high levels of alloparental care, even in the absence of reproductive experience. In previous studies, exposure to a pup was selectively associated with increased activity in oxytocin and vasopressin neurons along with decreased plasma corticosterone. In the present study, physiological, pharmacological and neuroanatomical methods were used to explore the autonomic and behavioral consequences of exposing male prairie voles to a pup. Reproductively naïve, adult male prairie voles were implanted with radiotransmitters used for recording ECG, temperature and activity. Males responded with a sustained increase in heart-rate during pup exposure. This prolonged increase in heart rate was not explained by novelty, locomotion or thermoregulation. Although heart rate was elevated during pup exposure, respiratory sinus arrhythmia (RSA) did not differ between these males and males exposed to control stimuli indicating that vagal inhibition of the heart was maintained. Blockade of beta-adrenergic receptors with atenolol abolished the pup-induced heart rate increase, implicating sympathetic activity in the pup-induced increase in heart rate. Blockade of vagal input to the heart delayed the males’ approach to the pup. Increased activity in brainstem autonomic regulatory nuclei was also observed in males exposed to pups. Together, these findings suggest that exposure to a pup activates both vagal and sympathetic systems. This unique physiological state (i.e. increased sympathetic excitation of the heart, while maintaining some vagal cardiac tone) associated with male caregiving behavior may allow males to both nurture and protect infants.

In search of an adult attachment stress provocation to measure effect on the oxytocin system: a pilot validation study

BACKGROUND

Oxytocin is a promising biomarker for psychiatric conditions arising from early relational trauma, childhood maltreatment, and attachment dysregulation, including posttraumatic stress and dissociative disorders.

OBJECTIVE

This exploratory pilot study examined plasma oxytocin as a biomarker for alterations in the attachment system.

DESIGN

We used a single group, repeated-measures design with 15 women. The protocol used a film clip previously validated as a provocation to the hypothalamic-pituitary-adrenal axis.

RESULTS

The repeated-measures ANOVA showed differences in oxytocin across the three time points. Correlations with oxytocin indicated that measures of dissociation and somatization correlated most strongly with higher levels of oxytocin measured during exposure to the film's bonding scene and posttraumatic stress disorder correlated most strongly with lower levels at the film's abandonment scene. Post hoc analyses revealed differences in oxytocin response related to psychopathology.

CONCLUSION

Replication studies should characterize participants on a range of psychiatric conditions associated with attachment dysregulation.

Peripheral vasopressin but not oxytocin relates to severity of acute psychosis in women with acutely-ill untreated first-episode psychosis

BACKGROUND

In women with chronic schizophrenia, higher levels of peripheral oxytocin have been associated with lower levels of positive but not negative symptoms. Sex-specific associations between endogenous levels of oxytocin (OT) and arginine vasopressin (AVP) with clinical symptoms and cognition in untreated early course patients have not been examined.

METHOD

Clinical ratings and neuropsychological testing were performed in thirty-eight acutely ill, unmedicated first-episode schizophrenia patients (14 women, 24 men). Serum hormone assays were obtained in patients and thirty-eight demographically similar healthy controls.

RESULTS

Patients demonstrated increased AVP levels compared to controls (p = 0.01). Higher AVP levels were associated with greater positive symptoms (r = 0.58, p = 0.03) and worse verbal learning (r = -0.63, p = 0.02) in female, but not male, patients. OT levels did not statistically differ between patients and controls, and were unrelated to clinical symptoms or cognition in patients.

CONCLUSION

Results suggest an association of endogenous AVP with increased positive symptom severity and worse cognition in untreated female, but not male, schizophrenia patients. Findings support the role of neuroendocrine alterations in acute psychosis and the importance of examining sex-specific neuroendocrine alterations early in the course of schizophrenia.

Exposure to chronic isolation modulates receptors mRNAs for oxytocin and vasopressin in the hypothalamus and heart

The goal of our study was to explore the effect of social isolation stress of varying durations on the plasma oxytocin (OT), messenger ribonucleic acid (mRNA) for oxytocin receptor (OTR), plasma arginine vasopressin (AVP) and mRNA for V1a receptor of AVP (V1aR) expression in the hypothalamus and heart of socially monogamous female and male prairie voles (Microtus ochrogaster). Continuous isolation for 4 weeks (chronic isolation) increased plasma OT level in females, but not in males. One hour of isolation every day for 4 weeks (repeated isolation) was followed by a significant increase in plasma AVP level. Chronic isolation, but not repeated isolation, significantly decreased OTR mRNA in the hypothalamus and heart in both sexes. Chronic isolation significantly decreased cardiac V1aR mRNA, but no effect on hypothalamic V1aR mRNA expression. We did not find a gender difference within repeated social isolation groups. The results of the present study reveal that although chronic social isolation can down-regulate gene expression for the OTR in both sexes, the release of the OT peptide was increased after chronic isolation only in females, possibly somewhat protecting females from the negative consequences of isolation. In both sexes repeated, but not chronic, isolation increased plasma AVP, which could be permissive for mobilization and thus adaptive in response to a repeated stressor. The differential effects of isolation on OT and AVP systems may help in understanding mechanisms through social interactions can be protective against emotional and cardiovascular disorders.

Preliminary evidence for lowered basal cortisol in a naturalistic sample of methamphetamine polydrug users

The effects of chronic methamphetamine use on neuroendocrine functioning in humans are largely undocumented. Here we assessed basal plasma oxytocin, arginine vasopressin, and cortisol levels in a naturalistic sample of methamphetamine polydrug users (n = 12) compared with controls matched for age, gender, education, occupation status, and marital status (n = 17). All of the methamphetamine users tested positive for blood methamphetamine and/or its main metabolite, amphetamine. Other drugs of abuse were detected in a small number of methamphetamine users (MDMA [3,4-methylenedioxy-N-methylamphetamine; n = 2], THC [delta-9-tetrahydrocannabinol; n = 2]). Almost half of the methamphetamine users reported using methamphetamine intravenously, and others smoked or ingested the drug. Methamphetamine users had significantly lower basal plasma cortisol (p = .025), but similar basal plasma oxytocin and arginine vasopressin levels compared with controls. Basal plasma oxytocin was positively correlated (p = .011), with basal plasma arginine vasopressin in controls, but not in methamphetamine users. Methamphetamine users reported higher rates of psychiatric symptoms including substance use disorders, impulsivity, and positive, negative, manic, and disorientation symptoms compared with controls. Psychiatric symptoms were not related to neuroendocrine functioning in either group. These results provide preliminary evidence for lowered basal cortisol levels in methamphetamine polydrug users and encourage further research in to the effects of methamphetamine on neuroendocrine functioning in humans using more highly controlled experimental research designs.

Oxytocin and vasopressin are dysregulated in Williams Syndrome, a genetic disorder affecting social behavior

The molecular and neural mechanisms regulating human social-emotional behaviors are fundamentally important but largely unknown; unraveling these requires a genetic systems neuroscience analysis of human models. Williams Syndrome (WS), a condition caused by deletion of ∼28 genes, is associated with a gregarious personality, strong drive to approach strangers, difficult peer interactions, and attraction to music. WS provides a unique opportunity to identify endogenous human gene-behavior mechanisms. Social neuropeptides including oxytocin (OT) and arginine vasopressin (AVP) regulate reproductive and social behaviors in mammals, and we reasoned that these might mediate the features of WS. Here we established blood levels of OT and AVP in WS and controls at baseline, and at multiple timepoints following a positive emotional intervention (music), and a negative physical stressor (cold). We also related these levels to standardized indices of social behavior. Results revealed significantly higher median levels of OT in WS versus controls at baseline, with a less marked increase in AVP. Further, in WS, OT and AVP increased in response to music and to cold, with greater variability and an amplified peak release compared to controls. In WS, baseline OT but not AVP, was correlated positively with approach, but negatively with adaptive social behaviors. These results indicate that WS deleted genes perturb hypothalamic-pituitary release not only of OT but also of AVP, implicating more complex neuropeptide circuitry for WS features and providing evidence for their roles in endogenous regulation of human social behavior. The data suggest a possible biological basis for amygdalar involvement, for increased anxiety, and for the paradox of increased approach but poor social relationships in WS. They also offer insight for translating genetic and neuroendocrine knowledge into treatments for disorders of social behavior.

Neuroendocrine and behavioural responses to exposure to an infant in male prairie voles

Paternal behaviour and pair-bond formation are defining characteristics of social monogamy. However, in comparison to pair-bonding, the endocrine factors associated with the male care of young are not well studied. In the present study, plasma concentrations of oxytocin, vasopressin and corticosterone (CORT) were measured in reproductively naïve male prairie voles as a function of exposure to an infant or control manipulations (i.e. handling or exposure to a wooden dowel). Plasma oxytocin concentrations were transiently elevated within 10 min of pup exposure. Although plasma CORT concentration typically increases after handling, after 10 min of pup exposure, the concentration of plasma CORT was not increased, suggesting an attenuation of CORT release by pup exposure. Group differences in the concentrations of plasma hormones were no longer detected at 20 or 60 min after treatment. These patterns of rapid change in the concentrations of plasma oxytocin and CORT were observed in both juvenile and adult males but not detected after control procedures. Plasma vasopressin, assessed only in adult males, did not vary as a function of pup exposure or other manipulations. In the paraventricular nucleus of the hypothalamus, pup exposure also increased activation (as assessed by the measurement of c-Fos) of neurones that stained for either oxytocin or vasopressin, whereas it decreased c-Fos expression in neurones stained for corticotrophin-releasing hormone. In addition, brief pup exposure (20 min) facilitated subsequent partner preference formation when alloparental males and pup attackers were considered as a group. In the context of other studies, these data support the hypothesis that neuroendocrine changes associated with male alloparental behaviour are related to those implicated in pair-bonding.

Peripheral oxytocin administration buffers autonomic but not behavioral responses to environmental stressors in isolated prairie voles

Negative social experiences such as social stressors and isolation influence mental and physical illnesses, including affective disorders and heart disease. Studies focused on socially monogamous prairie voles can provide insight into neurobiological systems that underlie the consequences of negative social interactions. Female prairie voles were exposed to 28 days of social isolation or pairing with a female sibling (control). Voles were administered daily oxytocin [20 μg/50 μl, subcutaneous (sc)] or saline vehicle (50 μl, sc) for 14 days and exposed to two behavioral stressors [elevated plus maze (EPM) and resident-intruder test]. Brain tissue was collected for analysis of central peptide levels in the hypothalamic paraventricular nucleus (PVN). Isolation produced autonomic changes [increased heart rate (HR) and decreased HR variability) during both acute stressors and increased anxiety behaviors in the EPM. Oxytocin injection prevented the autonomic consequences of the acute stressors in isolated prairie voles, but did not affect the behaviors tested under the present conditions. Oxytocin had no effect on the behavioral or autonomic responsiveness in paired prairie voles. Oxytocin injection may exert a beneficial effect on autonomic responses to stressors in isolated animals through increasing the number of oxytocin-containing neurons and decreasing the number of corticotropin-releasing hormone-containing neurons in the PVN. Oxytocinergic mechanisms may serve to compensate for autonomic responses associated with chronic isolation and exposure to both social and non-social acute stressors.

Sex-specific associations between peripheral oxytocin and emotion perception in schizophrenia

BACKGROUND

We previously reported that higher levels of peripheral oxytocin are associated with lower levels of positive, general, and overall symptoms in women but not in men with schizophrenia. Here we investigate the influence of sex, sex steroid hormone fluctuations, and peripheral oxytocin levels on emotional processing in men and women with schizophrenia.

METHOD

Twenty-two women with schizophrenia and 31 female controls completed the Penn Emotion Acuity Test (PEAT), a facial emotion recognition and perception task, during two menstrual cycle phases: 1) early follicular (Days 2-4; low estrogen/progesterone) and 2) midluteal (Days 20-22; high estrogen/progesterone). Twenty-six males with schizophrenia and 26 male controls completed testing at comparable intervals. We obtained plasma hormone assays of estrogen, progesterone, testosterone, and oxytocin.

RESULTS

No sex differences were noted on the PEAT. Plasma oxytocin levels did not fluctuate across phases of the menstrual cycle. However, female patients and controls more accurately identified facial emotions during the early follicular versus midluteal phase (p<0.05). Higher oxytocin levels related to perceiving faces as happier in both female patients (r=-0.46, p=0.04) and controls (r=-0.40, p=0.04) but not in men.

CONCLUSION

Like healthy women, women with schizophrenia demonstrate menstrual-cycle dependent fluctuations in recognizing emotional cues. Like healthy women, female patients with higher levels of oxytocin perceived faces as happier. Future studies need to address whether this sex-specific relationship is associated with trust and other positive emotions, and whether exogenous oxytocin might enhance mood states and social interaction in female or all schizophrenia patients.

Effects of social isolation on mRNA expression for corticotrophin-releasing hormone receptors in prairie voles

Previous studies have demonstrated that various type of stressors modulate messenger ribonucleic acid (mRNA) for type 1 corticotropin-releasing hormone (CRH) receptor (CRH-R1 mRNA) and type 2 CRH receptor (CRH-R2 mRNA). The purpose of this study was to explore the effect of social isolation stress of varying durations on the CRH, CRH-R1 and CRH-R2 mRNAs expression in the hypothalamus, hippocampus and pituitary of socially monogamous female and male prairie voles (Microtus ochrogaster). Isolation for 1h (single isolation) or 1h of isolation every day for 4 weeks (repeated isolation) was followed by a significant increase in plasma corticosterone levels. Single or repeated isolation increased hypothalamic CRH mRNA expression, but no changes in CRH-R1 mRNA in the hypothalamus were observed. Continuous isolation for 4 weeks (chronic isolation) showed no effect on hypothalamic CRH or CRH-R1 mRNAs in female or male animals. However, hypothalamic CRH-R2 mRNA was significantly reduced in voles exposed to chronic isolation. Single or repeated isolation, but not chronic isolation, significantly increased CRH-R1 mRNA and decreased CRH-R2 mRNA in the pituitary. Despite elevated CRH mRNA expression, CRH-R1 and CRH-R2 mRNAs were not modulated in the hippocampus following single or repeated isolation. Although, chronic isolation did not affect hippocampal CRH or CRH-R1 mRNAs, it did increase CRH-R2 mRNA expression in females and males. The results of the present study in prairie voles suggest that social isolation has receptor subtype and species-specific consequences for the modulation of gene expression for CRH and its receptors in brain and pituitary. Previous studies have revealed a female-biased increase in oxytocin in response to chronic isolation; however, we did not find a sex difference in CRH or its receptors following single, repeated or chronic social isolation, suggesting that sexually dimorphic processes beyond the CRH system, possibly involving vasopressin, might explain this difference.

Peripheral oxytocin is associated with reduced symptom severity in schizophrenia

BACKGROUND

Emerging evidence from clinical trials suggests that oral estrogen and intranasal oxytocin might reduce symptom severity in schizophrenia. Whether increases in endogenous hormones are similarly associated with improved symptoms is unknown. We investigated the effects of menstrual cycle phase and related fluctuations in peripheral hormone levels on clinical symptoms in women with chronic schizophrenia.

METHOD

Twenty-three women with schizophrenia were administered the Positive and Negative Syndrome Scale (PANSS), a measure of clinical symptom severity, at two menstrual cycle phases: 1) early follicular (Days 2-4; low estrogen/progesterone) and 2) midluteal (Days 20-22; high estrogen/progesterone). Twenty-seven males with schizophrenia and 58 controls (31 female) completed testing at comparable intervals. Men were included to examine whether the relationships between clinical symptoms and hormone levels in women generalize to men. Plasma hormone assays of estrogen, oxytocin, progesterone, and testosterone were obtained.

RESULTS

Female patients showed less severe symptoms during the midluteal versus early follicular phase (p's<0.01). Oxytocin did not fluctuate across phases, but in female patients (p's<0.01) higher oxytocin levels were associated with less severe positive symptoms and overall psychopathology. In both sexes, higher oxytocin levels were associated with more prosocial behaviors (p<0.05).

CONCLUSION

Consistent with previous findings in acutely ill patients, our results suggest that clinical symptoms vary across the menstrual cycle in patients with chronic schizophrenia. Similar to recent findings regarding benefits of intranasal oxytocin, these new findings indicate that high levels of endogenous oxytocin might improve positive symptom severity and general psychopathology in women and social behaviors in both sexes.

Marital behavior, oxytocin, vasopressin, and wound healing

Animal studies have implicated oxytocin and vasopressin in social bonding, physiological stress responses, and wound healing. In humans, endogenous oxytocin and vasopressin levels covary with perceptions of relationship quality, marital behaviors, and physiological stress responses. To investigate relationships among marital behavior, oxytocin, vasopressin, and wound healing, and to determine the characteristics of individuals with the highest neuropeptide levels, 37 couples were admitted for a 24-h visit in a hospital research unit. After small blister wounds were created on their forearm, couples participated in a structured social support interaction task. Blister sites were monitored daily following discharge to assess wound repair speed. Blood samples were collected for oxytocin, vasopressin, and cytokine analyses. Higher oxytocin levels were associated with more positive communication behaviors during the structured interaction task. Furthermore, individuals in the upper oxytocin quartile healed blister wounds faster than participants in lower oxytocin quartiles. Higher vasopressin levels were related to fewer negative communication behaviors and greater tumor necrosis factor-alpha production. Moreover, women in the upper vasopressin quartile healed the experimental wounds faster than the remainder of the sample. These data confirm and extend prior evidence implicating oxytocin and vasopressin in couples' positive and negative communication behaviors, and also provide further evidence of their role in an important health outcome, wound healing.

Detection of salivary oxytocin levels in lactating women

Oxytocin is a neuropeptide with widespread influence on many physiological and social functions including: labor and birth, lactation, sexual behavior, nurturing maternal behaviors, and stress reduction. However, our understanding of oxytocin's roles has been hampered by lack of noninvasive methods for assessing oxytocin levels. The goal of the present study was to assess whether oxytocin could be detected in saliva and whether changes occurred in the pattern of oxytocin release among lactating women from before, at initiation and after breast feeding. Using a prospective repeated measures design, 11 research participants each provided 18 saliva samples during three feeding cycles (before, at initiation and after breast feeding) for two 24-hr data collection periods (Days 1 and 2). Within each day, saliva was collected at late evening, early morning, and late morning. Salivary samples were concentrated fourfold by dehydration prior to analysis and oxytocin was measured in saliva using an enzyme immunoassay (EIA). Salivary oxytocin values, when reconverted to their original levels, ranged from 6.44 to 61.05 pg/ml. Oxytocin values in saliva varied significantly as a function of the breast feeding cycle, but did not show reliable differences as a function of the time of feeding. Oxytocin was highest before feeding, followed by a decrease at initiation of feeding, and an increase at 30 min after feeding. The findings suggest that oxytocin release into saliva increases in anticipation of feedings. This study also supports the potential usefulness of salivary measures of oxytocin as a noninvasive index of changes in this peptide.

Consequences of early experiences and exposure to oxytocin and vasopressin are sexually dimorphic

In the socially monogamous prairie vole, we have observed that small changes in early handling, as well as early hormonal manipulations can have long-lasting and sexually dimorphic effects on behavior. These changes may be mediated in part by changes in parental interactions with their young, acting on systems that rely on oxytocin (OT) and arginine vasopressin (AVP). Knowledge of both endogenous and exogenous influences on systems that rely on OT and AVP may be helpful in understanding sexually dimorphic developmental disorders, such as autism, that are characterized by increased anxiety and deficits in social behavior.

Social isolation modulates corticotropin-releasing factor type 2 receptor, urocortin 1 and urocortin 2 mRNAs expression in the cardiovascular system of prairie voles

The purpose of the present study was to examine the effect of social isolation stress on the expression of messengers ribonucleic acid (mRNAs) for corticotropin-releasing factor receptor type 2 (CRF2 receptor), urocortin 1 (Ucn 1) and urocortin 2 (Ucn 2) in the cardiovascular system of female and male prairie voles (Microtus ochrogaster). Isolation for 1 h (single isolation) or 1 h of isolation every day for 4 weeks (repeated isolation) was followed by a marked increase in plasma corticosterone level. However, continuous isolation for 4 weeks (chronic isolation) did not significantly affect plasma corticosterone level in female or male animals. A single period of isolation did not influence the expression of the CRF2 receptor, however, both repeated and chronic isolation significantly decreased CRF2 receptor mRNA in the ventricle and aorta of both sexes. Neither single nor chronic isolation significantly affected Ucn 1 mRNAs expression; however, repeated isolation increased Ucn 1 mRNA expression in the ventricles of female and male animals. Although, a single isolation produced no effect on cardiac Ucn 2 mRNA expression, both repeated and chronic isolation were followed by increased heart Ucn 2 mRNA expression in both sexes. We speculate that during repeated isolation Ucn 1 along with Ucn 2 are increased, which in turn down-regulates CRF2 receptor mRNA expression, and that Ucn 2 also may be one of factors responsible for the down-regulation of CRF2 receptor mRNA expression in cardiovascular system that is associated with chronic isolation.

Stress differentially modulates mRNA expression for corticotrophin-releasing hormone receptors in hypothalamus, hippocampus and pituitary of prairie voles

This study compares the effect of an acute stressor (restraint for 1h) versus a chronic stressor (social isolation for 4 weeks) on the expression of mRNAs for corticotropin-releasing hormone (CRH), CRH receptor type 1 (CRH-R1) and type 2 (CRH-R2) in the hypothalamus, hippocampus and pituitary of socially monogamous female prairie voles (Microtus ochrogaster). Animals were studied immediately following a stressor or as a function of repairing with a familiar sibling. Despite elevated expression of CRH mRNA, no alteration of CRH-R1 mRNA in the hypothalamus was observed following restraint stress or 4 weeks of social isolation. Hypothalamic CRH-R2 mRNA was significantly lower in voles exposed to restraint or isolation. CRH-R2 mRNA also remained down-regulated in isolated animals when these animals were re-paired with their sibling for one day following 28 days of isolation. Restraint, but not isolation, significantly increased CRH-R1 mRNA and decreased CRH-R2 mRNA in the pituitary. However, these differences were no longer observed when these animals were re-paired with their sibling for one day. Despite elevated CRH mRNA expression, CRH-R1 mRNA did not increase in the hippocampus following restraint or social isolation. Social isolation, but not restraint stress, increased CRH-R2 mRNA in the hippocampus, when these animals were re-paired with their sibling for one day the modulation of CRH mRNA remained up-regulated. Plasma corticosterone was elevated only following restraint, and not in animals that were handled, isolated or re-paired. The results of the present study reveal that acute restraint as well as social isolation can have significant consequences for the modulation of gene expression for the CRH receptors in brain and pituitary of prairie voles.

Oxytocin, vasopressin and sociality

The neurobiology of social behaviour is interwoven with autonomic, endocrine and other homoeostatic processes responsible for the adaptive functions of reproduction and survival. Young mammals are dependent on their mothers for nourishment, and the interaction between the mother and infant may be a physiological and neuroendocrine prototype for mammalian sociality. Although these adaptive functions of the mother-infant social behavioural dyad are obvious, adult social interactions, including social bonds, also are important to health and survival. Two neuropeptides, oxytocin (OXT) and arginine vasopressin (AVP), have been repeatedly implicated in mammalian social behaviours and emotional states that support sociality. Although best known for their roles in reproduction and homoeostasis, these peptides play a central role in the activation and expression of social behaviours and emotional states. Recent studies from our work with the prairie vole (Microtus ochrogaster), reviewed here, reveal a role for both OXT and AVP in behavioural and endocrine changes during social interactions, and also changes that are associated with the absence of social interactions (i.e. social isolation).

Oxytocin administration, but not social housing condition, reduces growth rate of human breast cancer xenografts (MCF7) in SCID mice

Abstract #5076

Background: Oxytocin decreases human breast cancer cell proliferation in vitro and oxytocin receptors are reported to be present on at least 80% of human breast tumors. Animal studies show increased oxytocin levels in association with pair bonding, maternal care giving and mating behavior. Our experiment tested two hypotheses: 1) exogenous administration of oxytocin(OT) and 2) sibling-group housing, compared to individual housing, will reduce the growth in human breast cancer cell -MCF7-xenografts in SCID mice. We also hypothesized this effect would be mediated by differences in circulating OT. Materials and Methods: A 2 X 2 design was used to study 48 animals. Half of the animals lived in group(GRP) housing, the others were housed singly(SGL). Half of the animals in each housing group received OT (10-9 M) administered by a continuous release pellet(Innovative Research of America) and the others received a placebo(PBO) pellet. At weaning(4 wks), SCID mice were randomized to individual cages vs. groups of 4 mice per cage. At maturation (vaginal cornification-8 wks), continuous release estrogen pellets were implanted and two days later MCF7 cells(0.1ml/10X106)were implanted in the mammary fat pad. Pellets containing OT or PBO were implanted, subcutaneously, 2 days after the MCF7 cells. Plasma was collected 2 days prior to and 2 days following pellet & cell implantation, 14 days later and at sacrifice (41 – 60 d) for analysis of OT concentration using enzyme immunoassay (Assay Designs, Inc). Tumor volumes were measured every three days. Statistical Analyses: A natural log transformation of the plasma OT levels was used to reduce skewness in the observed values. Tumor volumes were converted to cubed root to linearize and a regression line was fit to generate tumor growth rate(slope). Differences in tumor growth rate by housing condition (GRP/SGL), oxy Rx(Y/N) and OT plasma levels were tested by mixed effects ANOVA. Results: OT plasma levels in animals with OT pellets, as compared to PBO, were significantly different at 2 & 14 days after pellet implantation(p=0.001), but not at baseline or at sacrifice. OT plasma levels were higher in group vs single housing (p=.023). Due to the lack of difference in plasma OT at the time of sacrifice, we limited prediction of tumor growth rate to the first 29 days when OT pellets were secreting OT (extrapolation from levels at 2 & 14 days). Slower tumor growth rate occurred with OT treatment compared to PBO(p=0.031), and with higher OT plasma levels(p=0.032) but not with group vs. single housing.&#x2028; Discussion: Continuous oxytocin administration over 29 days produced increased oxytocin plasma levels and both were associated with reduced MCF7 xenograft growth rate in SCID mice. Our next step will be to test whether breast tumor oxytocin receptor density moderates the association between plasma oxytocin and tumor growth rate.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5076.

Neonatal oxytocin treatment modulates oxytocin receptor, atrial natriuretic peptide, nitric oxide synthase and estrogen receptor mRNAs expression in rat heart

Oxytocin (OT) has been implicated in reproductive functions, induction of maternal behavior as well as endocrine and neuroendocrine regulation of the cardiovascular system. Here we demonstrate that neonatal manipulation of OT can modulate the mRNAs expression for OT receptor (OTR), atrial natriuretic peptide (ANP), endothelial nitric oxide synthase (eNOS) and estrogen receptor alpha (ERalpha) in the heart. On the first day of postnatal life, female and male rats were randomly assigned to receive one of the following treatments: (a) 50microl i.p. injection of 7microg OT; (b) 0.7microg of OT antagonist (OTA); or (c) isotonic saline (SAL). Hearts were collected either on postnatal day 1 or day 21 (D1 or D21) and the mRNAs expression of OTR, ANP, inducible NOS (iNOS), eNOS, ERalpha and estrogen receptor beta (ERbeta) were compared by age, treatment, and sex utilizing real time PCR. OT treatment significantly increased heart OTR, ANP and eNOS mRNAs expression on D1 in both males and females, ERalpha increased only in females. While there were significant changes in the relative expression of all types of mRNA between D1 and D21, there were no significant treatment effects observed in D21 animals. OTA treatment significantly decreased basal ANP and eNOS mRNAs expression on D1 in both sexes. The results indicate that during the early postnatal period OT can have an immediate effect on the expression OTR, ANP, eNOS, and ERalpha mRNAs and that these effects are mitigated by D21. Also with the exception of ERalpha mRNA, the effects are the same in both sexes.

Oxytocin: behavioral associations and potential as a salivary biomarker

Oxytocin (OT) is a neuropeptide that is produced primarily in the hypothalamus and is best known for its role in mammalian birth and lactation. Recent evidence also implicates OT in social behaviors, including parental behavior, the formation of social bonds, and the management of stressful experiences. OT is reactive to stressors, and plays a role in the regulation of both the central and autonomic nervous system, including effects on immune and cardiovascular function. Knowledge of patterns of OT release would be of value in many fields of science and medicine. However, measurements of OT concentration in blood are infrequently performed, and previous attempts to measure OT in saliva have been unsuccessful. Using a sensitive enzyme immunoassay (EIA) and concentrated samples we were able to detect reproducible changes in salivary OT as a function of lactation and massage. These results indicate that measurements of biologically relevant changes in salivary OT are possible. These results confirm the biological relevance of changes in salivary OT with stressors and support saliva as a noninvasive source to monitor central neuroendocrine function.

Modulation of cardiac oxytocin receptor and estrogen receptor alpha mRNAs expression following neonatal oxytocin treatment

Oxytocin (OT) is known for its role in reproduction. However, evidence has emerged suggesting its involvement in the regulation of the cardiovascular system. Here we examine the hypothesis that neonatal exposure to OT can have both short-term and long-lasting consequences on gene expression in heart tissue. On the first day of postnatal life, female and male prairie voles (Microtus ochrogaster) were randomly assigned to receive one of following treatments: 50 microl i.p. injection of (a) 3 microg OT (b) 0.3 microg of OT antagonist (OTA), or (c) isotonic saline (SAL). Hearts were collected on postnatal day 1 (D1, 2 h after injection), day 8 (D8), or day 21 (D21), and the mRNA expression for OT receptor (OTR), estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta as a function of age, treatment, and sex were measured using RT-PCR. Neonatal treatment with OT showed a marked increase in cardiac OTR mRNA expression on postnatal D1, but not D8 or D21, in both female and male animals. ERalpha increased as a function of OT treatment only in females. Although significant treatment effects were no longer detected in D8 or D21 animals, there were significant changes in the relative expression of all types of mRNA between D1 and D21 with age-related declines in OTR and ERbeta and increases in ERalpha Neonatal treatment with OTA showed no changes in cardiac OTR, ERalpha, or ERbeta mRNAs expression. The results indicate that during the early postnatal period OT can have rapid effects on the expression of OTR and ERalpha mRNAs and that these effects are mitigated by D8 or D21. Also, with the exception of ERalpha mRNA, the effects are the same in both sexes.

Oxytocin selectively increases ERalpha mRNA in the neonatal hypothalamus and hippocampus of female prairie voles

During neonatal development exogenous oxytocin increases ERalpha immunoreactivity in the hypothalamus of female prairie voles. The purpose of this study was to determine if the increase in ERalpha is associated with an increase in ERalpha mRNA expression and to determine if the effect is specific to ER subtype or if oxytocin also influences ERbeta mRNA expression. On the day of birth female prairie vole pups were treated with oxytocin, an oxytocin antagonist, or saline. Brains were collected and RT-PCR was used to determine the effect of treatment on ER mRNA production in the hypothalamus, hippocampus, and cortex. Within 2h of treatment oxytocin significantly increased ERalpha mRNA expression in the hypothalamus and hippocampus, but not the cortex, while inhibiting the effects of endogenous oxytocin reduced the expression of ERalpha mRNA in the hippocampus. Neonatal treatment did not affect the expression of ERbetamRNA. The results demonstrate that the effects of oxytocin treatment are region and ER subtype specific and that during the neonatal period oxytocin can affect the expression of ERalpha by altering message production. The regional specific changes in ERalpha mRNA expression in females are consistent with studies examining the behavioral and physiological effects of neonatal manipulation of oxytocin in females.

Modulation of corticotropin-releasing hormone type 2 receptor and urocortin 1 and urocortin 2 mRNA expression in the cardiovascular system of prairie voles following acute or chronic stress

The purpose of this study was to compare the effects of an acute stressor (restraint) versus a chronic stressor (social isolation) on the expression of mRNAs for corticotropin-releasing hormone receptor type 2 (CRH-R2) and urocortin 1 (Ucn 1) and urocortin 2 (Ucn 2) in the cardiovascular system of socially monogamous prairie voles of both sexes. Acute restraint for 1 h was followed by a marked increase in plasma corticosterone, and when the animals were re-paired for 1 day, the increment of corticosterone was normalized. However, following chronic social isolation for 4 weeks, plasma corticosterone did not differ significantly from the levels measured in animals living in pairs. Restraint or isolation significantly decreased CRH-R2 mRNA in ventricle, atria, and aorta; however, when these animals were re-paired for 1 day, the modulation of CRH-R2 mRNA was normalized in restraint but not in isolated animals. Restraint stress increased the Ucn 1 mRNA expression in the heart of female and male prairie voles, and when the animals were re-paired, the modulation of Ucn 1 mRNA expression was normalized. However, chronic isolation showed no effect on cardiac Ucn 1 mRNA expression. Although acute restraint stress produced no effect on the cardiac Ucn 2 mRNA expression, chronic isolation was followed by an increased heart Ucn 2 mRNA expression in both sexes. When the isolated animals were re-paired for 1 day, the cardiac Ucn 2 mRNA expression remained upregulated. The results of the present study reveal that acute restraint as well as social isolation can have significant consequences for the modulation of gene expression for the CRH-R2 and the urocortin peptides in cardiovascular tissue in female and male prairie voles.

Physiological and behavioral responses to interleukin-1beta and LPS in vagotomized mice

It is well established that peripheral administration of interleukin-1 (IL-1) and lipopolysaccharide (LPS) can activate the hypothalamo-pituitary-adrenocortical (HPA) axis, alter brain catecholamine and indoleamine metabolism, and affect behavior. However, the mechanisms of these effects are not fully understood. Stimulation of afferents of the vagus nerve has been implicated in the induction of Fos in the brain, changes in body temperature, brain norepinephrine, and some behavioral responses. In the present study, the IL-1beta- and LPS-induced changes in certain behaviors, HPA axis activation, and catecholamine and indoleamine metabolism were studied in mice following subdiaphragmatic vagotomy. IL-1beta and LPS induced the expected decreases in sweetened milk, food intake, and locomotor activity, and the responses to IL-1beta, but not LPS, were slightly attenuated in vagotomized mice. Subdiaphragmatic vagotomy also attenuated the IL-1beta- and LPS-induced increases in plasma ACTH and corticosterone, but the attenuations of the responses to IL-1beta were only marginally significant. There were also slight reductions in the responses in catecholamine and serotonin metabolism, and the increases in brain tryptophan in several brain regions. These results indicate that the vagus nerve is not the major pathway by which abdominal IL-1beta and LPS effect behavioral, HPA and brain catecholamine and indoleamine responses in the mouse. These results resemble those we observed in subdiaphragmatically vagotomized rats, but in that species the subdiaphragmatic vagotomy markedly attenuated the ACTH and corticosterone responses, and prevented the hypothalamic noradrenergic activation, as well as the fever. Overall the results indicate that the various responses to peripheral IL-1 and LPS involve multiple mechanisms including vagal afferents, and that there are species differences in the relative importance of the various mechanisms.