Corticotropin-releasing hormone and opioid peptides in reproduction and stress

Endorphins, Sexuality, and Reproduction

Beta-endorphin is secreted from the hypothalamus and pituitary in both mother and newborn. The placenta produces numerous pituitary hormones from the third month of pregnancy, one of which is βE. It has been suggested that βE has a role in the appetitive and precopulatory phase of sexual behavior in animals. An increase in endorphin levels during sexual activity in humans may contribute to attachment and bonding between partners, but contradictory reports in the literature question the association between sexuality and βE levels. The level of βE also increases during pregnancy, rises in early labor, peaks in late labor, and drops in the postpartum period. This fluctuation provides natural analgesia, raises the pain threshold, decreases the sensation of pain, or suppresses pain, and decreases fear levels during labor and birth. Beta-endorphin also protects the fetus from hypoxia during labor and birth and potential neural damage by aiding blood flow to the brain under hypoxic conditions. It has been suggested that a variety of pharmacologic and nonpharmacologic complementary therapies, when used in pregnancy, labor, and birth, activate the opioid receptors in the CNS and alter the sensation of pain during labor and birth, affect the mother-child attachment and affect sexual function. These studies report contradictory results that will be discussed in this chapter.

Serum oxytocin and corticotropin-releasing hormone levels in the third trimester of pregnancy for predicting postpartum depression in Thai women

PURPOSE

This prospective observational study aimed to determine whether serum oxytocin (OT) or corticotrophin-releasing hormone (CRH) levels in the third trimester of pregnancy (or late pregnancy) could prospectively predict postpartum depression (PPD) at six weeks after childbirth.

METHODS

We measured late pregnancy OT and CRH levels in Thai women, assessed depression using the Edinburgh Postnatal Depression Scale (EPDS) and Patient Health Questionnaire-9 (PHQ-9), and collected mothers, labor, and newborn data. At six weeks postpartum, an EPDS score ≥ 11 or PHQ-9 score ≥ 10 was defined as the presence of PPD. Multivariable binary logistic regression analysis was performed to determine the predictors of PPD.

RESULTS

Of 200 participants, 136 (68.0%) were reassessed at six weeks postpartum, and 19 of them (14.0%) had PPD. Of the 19 participants with PPD, 9 met the EPDS criterion only, 3 met the PHQ-9 criterion only, and 7 met both criteria. OT levels were not significantly different between those with and without PPD (p = 0.35). CRH levels (aOR = 1.011, 95% CI = 1.001-1.023, p = 0.041), DASS-21 stress (aOR = 1.259, 95% CI = 1.132-1.400, p < 0.001), and APGAR at 1 min (aOR = 0.425, 95% CI = 0.240-0.752, p = 0.003) were significant predictors of PPD.

CONCLUSIONS

Only high CRH but not OT levels in late pregnancy may predict 6-week PPD. However, combining these CRH levels, late pregnancy stress, and newborn well-being immediately after birth seems to increase the accuracy of PPD prediction.

Prenatal phthalate exposure in relation to placental corticotropin releasing hormone (pCRH) in the CANDLE cohort

CONTEXT

Phthalates may disrupt maternal-fetal-placental endocrine pathways, affecting pregnancy outcomes and child development. Placental corticotropin releasing hormone (pCRH) is critical for healthy pregnancy and child development, but understudied as a target of endocrine disruption.

OBJECTIVE

To examine phthalate metabolite concentrations (as mixtures and individually) in relation to pCRH.

DESIGN

Secondary data analysis from a prospective cohort study.

SETTING

Prenatal clinics in Tennessee, USA.

PATIENTS

1018 pregnant women (61.4% non-Hispanic Black, 32% non-Hispanic White, 6.6% other) participated in the CANDLE study and provided data. Inclusion criteria included: low-medical-risk singleton pregnancy, age 16-40, and gestational weeks 16-29.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Plasma pCRH at two visits (mean gestational ages 23.0 and 31.8 weeks) and change in pCRH between visits (ΔpCRH).

RESULTS

In weighted quantile sums (WQS) regression models, phthalate mixtures were associated with higher pCRH at Visit 1 (β = 0.07, 95 %CI: 0.02, 0.11) but lower pCRH at Visit 2 (β = -0.08, 95 %CI: -0.14, -0.02). In stratified analyses, among women with gestational diabetes (n = 59), phthalate mixtures were associated with lower pCRH at Visit 1 (β = -0.17, 95 %CI: -0.35, 0.0006) and Visit 2 (β = -0.35, 95 %CI: -0.50, -0.19), as well as greater ΔpCRH (β = 0.16, 95 %CI: 0.07, 0.25). Among women with gestational hypertension (n = 102), phthalate mixtures were associated with higher pCRH at Visit 1 (β = 0.20, 95 %CI: 0.03, 0.36) and Visit 2 (β = 0.42; 95 %CI: 0.19, 0.64) and lower ΔpCRH (β = -0.17, 95 %CI: -0.29, -0.06). Significant interactions between individual phthalate metabolites and pregnancy complications were observed.

CONCLUSIONS

Phthalates may impact placental CRH secretion, with differing effects across pregnancy. Differences in results between women with and without gestational diabetes and gestational hypertension suggest a need for further research examining whether women with pregnancy complications may be more vulnerable to endocrine-disrupting effects of phthalates.

The Infertility Trap: The Fertility Costs of Group-Living in Mammalian Social Evolution

Mammal social groups vary considerably in size from single individuals to very large herds. In some taxa, these groups are extremely stable, with at least some individuals being members of the same group throughout their lives; in other taxa, groups are unstable, with membership changing by the day. We argue that this variability in grouping patterns reflects a tradeoff between group size as a solution to environmental demands and the costs created by stress-induced infertility (creating an infertility trap). These costs are so steep that, all else equal, they will limit group size in mammals to ∼15 individuals. A species will only be able to live in larger groups if it evolves strategies that mitigate these costs. We suggest that mammals have opted for one of two solutions. One option (fission-fusion herding) is low cost but high risk; the other (bonded social groups) is risk-averse, but costly in terms of cognitive requirements.

Social structure as a strategy to mitigate the costs of group living: a comparison of gelada and guereza monkeys

In mammals, and especially primates, group size and social complexity are typically correlated. However, we have no general explanation why this is so. I suggest that the answer may lie in one of the costs of group living: mammalian reproductive endocrinology is extremely sensitive to stress, and forms one of the hidden costs of living in groups. Fertility declines with group size widely across the social mammals, including primates, and will ultimately place a constraint on group size. However, some species seem to have been able to mitigate this cost by forming bonded relationships that reduce the impact of experienced aggression, even if rates of aggression remain high. The downside is that they reduce network connectivity and hence risk fragmenting the group by providing fracture lines for group fission. To explore this, I compare network indices and fertility patterns across the same range of group sizes for two species of Old World monkeys, Colobus guereza and Theropithecus gelada: the former relatively unsocial, the latter intensely social with frequent use of grooming-based alliances. Compared to those of the guereza, gelada social networks lose density more slowly, maintain connectedness more effectively and are less likely to fragment as they increase in size. Although fertility declines with group size in both species, in gelada the impact of this effect is deferred to larger group sizes. The differences in fertility and network structure both predict the very different maximum group sizes typical of these two species, as well as the typical sizes at which their groups undergo fission. This finding may explain aspects of wider mammalian sociality.

Cell type-specific and time-dependent light exposure contribute to silencing in neurons expressing Channelrhodopsin-2

Channelrhodopsin-2 (ChR2) has quickly gained popularity as a powerful tool for eliciting genetically targeted neuronal activation. However, little has been reported on the response kinetics of optogenetic stimulation across different neuronal subtypes. With excess stimulation, neurons can be driven into depolarization block, a state where they cease to fire action potentials. Herein, we demonstrate that light-induced depolarization block in neurons expressing ChR2 poses experimental challenges for stable activation of specific cell types and may confound interpretation of experiments when ‘activated’ neurons are in fact being functionally silenced. We show both ex vivo and in vivo that certain neuronal subtypes targeted for ChR2 expression become increasingly susceptible to depolarization block as the duration of light pulses are increased. We find that interneuron populations have a greater susceptibility to this effect than principal excitatory neurons, which are more resistant to light-induced depolarization block. Our results highlight the need to empirically determine the photo-response properties of targeted neurons when using ChR2, particularly in studies designed to elicit complex circuit responses in vivo where neuronal activity will not be recorded simultaneous to light stimulation.

DOI:http://dx.doi.org/10.7554/eLife.01481.001

The brain is a highly complex structure composed of trillions of interconnecting nerve cells. The pattern of connections between these cells gives rise to the various brain circuits that govern how the brain functions. Understanding how the brain is wired together is important for determining how ‘faulty circuits’ contribute to various neurological disorders.

New optogenetic technique tools allow neuroscientists to turn on specific neurons simply by shining light on them. These techniques involve genetically manipulating the organisms so that their neurons express proteins that are activated when they are exposed to light of a particular wavelength. However, it is important to understand the limitations of this approach—including the possibility that the light might actually turn off some neurons—when using it to study animal behavior.

Now, Herman, Huang et al. show that shining light pulses for long durations onto neurons expressing a light-activated protein called channelrhodopsin-2 causes the neurons to become silenced rather than activated. Moreover, certain types of neurons, called interneurons, are more susceptible to this effect—termed ‘depolarization block’—than the other types of neurons.

Researchers need to be mindful of this effect when channelrhodopsin-2 is used in optogenetic experiments to study the behavior of living animals. However, this silencing property could be useful in experiments that investigate situations in which depolarization block is thought to contribute to brain function and health: such as in the treatments of schizophrenia and Parkinson’s disease.

DOI:http://dx.doi.org/10.7554/eLife.01481.002

Resolution of anovulation infertility using neuro emotional technique: a report of 3 cases

BACKGROUND

The female menstrual cycle is a complicated interaction of hormonal messages that are under the control of the Hypothalamic-Pituitary-Ovarian axis. Dysfunction in this axis can lead to anovulation and infertility. Stress has the potential to produce such dysfunction.

OBJECTIVES

To review the normal menstrual cycle, and present a number of case studies on how the stress- reducing technique of Neuro Emotional Technique (NET) successfully aided the fertility of a number of female patients by resolving anovulation/menstrual irregularity.

METHODS

Three chronic anovulating, infertile patients underwent NET. A visual analog scale was used to evaluate the effectiveness of the intervention.

OUTCOMES

Anovulating patients started to ovulate following a series of treatments. Initial visual analog scale (VAS) scale on menstrual irregularity was rated 10 out of a possible 10 (anovulation) for all patients. After treatment, these 3 patients rated 0 out of 10 on the VAS scale and had fallen pregnant with subsequent birthing. A discussion of the potential link between stress and anovulation through altered gonadotropin releasing hormone pulsitile activity and how the use of NET may have resolved the anovulation seen in these 3 patients is presented.

CONCLUSION

The success attributed to the NET intervention and the resumption of ovulation warrant the need for further research involving long term prospective randomized controlled trial experiments to determine a direct causal relationship.

Rhythmic clock and neuropeptide gene expression in hypothalamic mHypoE-44 neurons

The rhythmic expression of specific clock genes: Bmal1, Per2, Clock and Rev-Erbalpha; and specific hypothalamic neuropeptides: NPY, Crh, AgRP, neurotensin and preproghrelin, expressed in clonal hypothalamic neuronal cell lines, was assayed and analyzed using a novel non-linear least squares statistical analysis to determine rhythmicity in an in vitro milieu. In silico analysis of the neuropeptide promoter regions identified putative E-box motifs and a motif in the NPY promoter is bound to in an oscillatory fashion. Within the mHypoE-44 neurons, we demonstrate that mRNA of four core circadian components: Bmal1, Clock, Per2 and Rev-Erbalpha, oscillate with approximate 24h rhythms. NPY and NT demonstrated significant 24h gene expression. However, CRH and preproghrelin mRNA cycled significantly in an ultradian fashion, oscillating approximately every 18h. AgRP mRNA did not show a significant rhythm. We speculate that endogenous rhythmic neuropeptide expression contributes to neuroendocrine homeostasis, which may include energy balance.

The association of pain and depression in preadolescent girls: moderation by race and pubertal stage

OBJECTIVE

To test whether an association between pain response and depression in females is present during preadolescence using a controlled pain stimulus and a clinically relevant assessment of depressive symptoms.

METHOD

In a sample of 232 girls, pain threshold and tolerance were assessed at age 10 years using the cold pressor task, and a diagnostic interview was used to assess depression symptoms at 10 and 11 years of age.

RESULTS

Response to pain at age 10 was associated with depressive symptoms at ages 10 and 11; race and pubertal stage moderated the association. Pain response and depression were more strongly associated among girls who had reached advanced stages of pubertal development and among European American girls.

CONCLUSIONS

The results add to the existing literature on the co-occurrence of depression and pain by demonstrating modest but consistent concurrent and prospective associations between response to pain and depression among girls during preadolescence.

Response to delivery stress is not mediated by beta-endorphin (1–31)

OBJECTIVE

The aim of the study was to determine the reaction of the melanotroph and corticotroph-type pituitary proopiomelanocortin (POMC) response to vaginal delivery and caesarean section stress. Furthermore, the relationship between the release of pituitary POMC fragments, gonadotropins and sexual steroids were examined.

STUDY DESIGN

Blood samples were obtained from 10 women in labour on arrival in the birth room (t(A)), at cervix dilatation of 5 cm (t(B)) and immediately after spontaneous delivery (t(C)) and in 16 patients undergoing elective caesarean section before induction of anaesthesia (t(B)) and immediately after delivery (t(C)). Samples were analysed for cortisol, ACTH, authentic beta-endorphin, beta-endorphin immunoreactive material (IRM), acetyl-N-beta-endorphin IRM (NAC), beta-lipotropin (beta-LPH) IRM, oestradiol (E(2)), progesterone (P), prolactin (PRL), FSH and LH.

RESULTS

NAC representing the melanotroph-type pituitary POMC system did not increase during the course of caesarean section or spontaneous labour. In contrast, a significant increase of beta-endorphin IRM, beta-LPH IRM and ACTH were observed, representing an activation of the corticotroph-type POMC system. Highly significant correlations between POMC fragment concentrations during caesarean section and spontaneous labour were also observed. Sexual steroids (E(2) and P) decreased significantly. Except for beta-endorphin IRM and E(2) in course of spontaneous delivery no significant correlation was observed between POMC fragment and gonadotropins or sexual steroids.

CONCLUSION

Caesarean section and spontaneous delivery activated the corticotroph but not the melanotroph POMC system.

Norepinephrine, adrenocorticotropin, cortisol and beta-endorphin in women suffering from fear of labor: responses to the cold pressor test during and after pregnancy

BACKGROUND

Women suffering from fear of labor have reduced pain tolerance during a cold pressor test (CPT) during and after pregnancy.

METHODS

We compared levels of norepinephrine, adrenocorticotropin (ACTH), cortisol and beta-endorphin before and during the CPT up to 60 min in 20 normotensive women with and 20 without fear of labor at 37.4 +/- 0.2 (mean +/- SE) gestational weeks and at 41.9 +/- 1.6 weeks after delivery.

RESULTS

Baseline levels of norepinephrine in the pregnant fear group (1.63 +/- 0.18 nmol/L) were higher (p = 0.068) than in controls (1.38 +/- 0.14 nmol/L) but after delivery they were lower in the fear group (1.75 +/- 0.31 nmol/L vs. 2.31 +/- 0.26 nmol/L, p = 0.064). ACTH, cortisol and beta-endorphin did not differ between pregnant and nonpregnant groups. The CPT caused a 28.4% smaller response in norepinephrine in the pregnant fearful women than in controls, whereas the responses of ACTH and beta-endorphin were similar between groups during and after pregnancy. The CPT caused no significant response in cortisol. Pregnant fearful women had higher diastolic blood pressure (85.6 +/- 4.5 mmHg, mean +/- SE) than the controls (74.9 +/- 3.4 mmHg, p = 0.065).

CONCLUSIONS

Women with fear of labor were characterized by changes in norepinephrine but not in ACTH, cortisol or beta-endorphin before and during the CPT, indicating a normal pituitary-adrenal axis function.

Ovarian Dysfunction, Stress, and Disease: A Primate Continuum

Menopause is recognized as a period of increased risk for coronary heart disease (CHD) and osteoporosis. Vulnerability to these conditions is often attributed to the naturally occurring estrogen deficiency characteristic of this part of the life cycle. Premenopausal reductions in endogenous estrogen occasioned by functional ovarian abnormalities or failure are hypothesized to be similarly pathogenic and to accelerate development of CHD and osteoporosis prematurely, thereby increasing the health burden of older women. These functional abnormalities, which occur along a continuum from mild, luteal phase progesterone deficiency to amenorrhea, are relatively common and are often attributed to psychogenic factors (stress, anxiety, depression, or other emotional disturbance), exercise, or energy imbalance. Although numerous investigators have commented on these functional deficits, the abnormalities can be difficult to diagnose and are generally unappreciated for the contribution they may make to postmenopausal disease. Studies in nonhuman primates confirm that these deficits are easily induced by psychological stress and exercise, and that they accelerate the development of cardiovascular disease and perhaps bone loss in the presence of a typical North American diet. However, functional reproductive deficits are also reversible and are thus potentially amenable to environmental or behavioral intervention. Data from both women and nonhuman primates support the hypothesis that functional reproductive deficits are adaptive when triggered appropriately but are detrimental when activated in an environment (e.g., sedentary lifestyle, high-fat diet) permissive to the development of chronic disease.

Stress and female reproductive function: A study of daily variations in cortisol, gonadotrophins, and gonadal steroids in a rural Mayan population

We report here on a longitudinal study of stress and women's reproduction in a small Kaqchikel Mayan community in rural Guatemala. Current understanding of the effects of stress on the reproductive axis in women is mostly derived from clinical studies of individual stressors. Little is known, however, about the cumulative effects of "real life" stress. Cortisol increases in response to a broad variety of individual stressors (Tilbrook et al., 2002). In this article, we evaluate the association between daily fluctuations in women's urinary cortisol and reproductive hormones: estrone conjugates (E(1)C), pregnandiol glucuronide (PdG), luteinizing hormone (LH), and follicle stimulating hormone (FSH). To assess the association between daily changes in cortisol levels and changes in the profiles of the reproductive hormones, we used a random coefficients model based on polynomial regression. The sample includes 92 menstrual cycles provided by 24 participants over a year-long prospective study. Increases in urinary cortisol levels were associated with significant increases in gonadotrophin and progestin levels during the follicular phase. Also, in a time window between days 4 and 10 after ovulation, increased cortisol levels were associated with significantly lower progestin levels. These results are significant because untimely increases in gonadotrophins and low midluteal progesterone levels have previously been reported to impinge on the ovulatory and luteinization processes and to reduce the chances of successful implantation (Ferin, 1999; Baird et al., 1999). Future research should consider the possibility that stress may affect fecundability and implantation without necessarily causing amenorrhoea or oligomenorrhoea.

Leptin, neuropeptide Y, beta-endorphin, gonadotropin, and estradiol levels in girls before menarche

More than two decades of clinical studies have provided us with the opportunity to develop and implement criteria that distinguish three phases during pre-menarche, paralleling rising levels of estrogens, namely 'pre-estrogenization', 'onset of estrogenization' and 'full estrogenization'. The aim of this study was to examine the relationships between somatic features and levels of leptin, neuropeptide Y (NPY), beta-endorphin, gonadotropin and estradiol in pubertal girls before menarche. Weight, height, body mass index (BMI), tertiary sex features, estrogen-related changes in hymen, fat and lean body mass were studied on a quarterly basis in 45 girls. At the same time, ovarian and uterine dimensions were established sonographically and serum was obtained for the determination of leptin, NPY, beta-endorphin, gonadotropin, and estradiol levels. Onset of estrogenization in girls was marked by weight loss, followed by an increase in total, fat and lean body mass, and pubertal acceleration of growth. At the time of full estrogenization, lower NPY and beta-endorphin levels were observed, accompanied by an increase in gonadotropin secretion. Changes in leptin levels are consistent with a role of this hormone in metabolic signaling.

Alterations induced by gestational stress in brain morphology and behaviour of the offspring

Retrospective studies in humans suggest that chronic maternal stress during pregnancy, associated with raised plasma levels of CRH, ACTH and cortisol may increase the likelihood of preterm birth, developmental delays and behavioural abnormalities in the children. In adulthood, it may contribute to the significant association between the incidence of schizophrenia, increased left or mixed handedness, reduction in cerebral asymmetry and anomalies in brain morphology. Our studies and others have shown that prenatal stress in rats can mimic these developmental and behavioural alterations. These rats show a reduced propensity for social interaction, increased anxiety in intimidating or novel situations and a reduction in cerebral asymmetry and dopamine turnover, consistent with those in schizophrenic humans. Prenatally-stressed (PS) rats also show behaviour consistent with depression, including a phase-shift in their circadian rhythm for corticosterone, sleep abnormalities, a hedonic deficit and greater acquisition of learned helplessness under appropriate conditions. These behavioural abnormalities are associated with impaired regulation of the hypothalamic-pituitary-adrenal axis response to stress and increased CRH activity. PS males may show demasculinisation and feminisation of their sexual behaviour. The developmental and behavioural abnormalities in PS offspring could occur through sensitisation of the foetal brain by maternal stress hormones to the action of glucocorticoid and CRH and to neurotransmitters affected by them. This may have long-lasting consequences and could explain the precipitation of depressive symptoms or schizophrenia by psychosocial stress in later life. The character of the behavioural abnormalities probably depends on the timing of the maternal stress in relation to development of the particular neuronal systems.

Neurobiological mechanisms of the onset of puberty in primates

An increase in pulsatile release of LHRH is essential for the onset of puberty. However, the mechanism controlling the pubertal increase in LHRH release is still unclear. In primates the LHRH neurosecretory system is already active during the neonatal period but subsequently enters a dormant state in the juvenile/prepubertal period. Neither gonadal steroid hormones nor the absence of facilitatory neuronal inputs to LHRH neurons is responsible for the low levels of LHRH release before the onset of puberty in primates. Recent studies suggest that during the prepubertal period an inhibitory neuronal system suppresses LHRH release and that during the subsequent maturation of the hypothalamus this prepubertal inhibition is removed, allowing the adult pattern of pulsatile LHRH release. In fact, y-aminobutyric acid (GABA) appears to be an inhibitory neurotransmitter responsible for restricting LHRH release before the onset of puberty in female rhesus monkeys. In addition, it appears that the reduction in tonic GABA inhibition allows an increase in the release of glutamate as well as other neurotransmitters, which contributes to the increase in pubertal LHRH release. In this review, developmental changes in several neurotransmitter systems controlling pulsatile LHRH release are extensively reviewed.

Fetal placental vascular responses to corticotropin-releasing hormone in vitro. Effects of variation in oxygen tension

In this study, using the human placenta perfused in vitro with Krebs' bicarbonate solution, we have examined the effects of changes in oxygen tension on the vasoreactivity of fetal placental blood vessels to corticotropin releasing hormone (CRH). Vasodilatory responses to human synthetic CRH were measured during sub-maximal vasoconstriction of the fetal placental circulation with prostaglandin F(2alpha)(PGF(2alpha)) (1-100 micrometer). Decreases in fetal placental arterial perfusion pressure (FAP) were obtained with CRH under conditions of high oxygen or low oxygen tension, >/=450 mmHg and </=50 mmHg, respectively. Secretion of CRH into the maternal and fetal placental circulations was measured during changes in oxygen tension in normal placentae and placentae from abnormal pregnancies complicated by pre-eclampsia. The change from high to low oxygen perfusion resulted in a small increase in the basal perfusion pressure (21+/-3.6 to 28.3+/-2.6 mmHg; (P</= 0.001, Student's paired t -test). During high oxygen perfusion, CRH (0. 3-3000 p m) caused a concentration dependent reduction of the PGF(2alpha)induced increase in FAP. However, during low oxygen perfusion, the vasodilatory effects of CRH were completely inhibited (P</= 0.05, regression analysis, ANOVA). The effect of the NO synthase inhibitor l -nitro-omega-arginine methyl ester (l -NAME, 1-100 micrometer), on basal FAP during high and low oxygen conditions was also established. Low oxygen perfusion significantly attenuated l -NAME-induced increases in perfusion pressure (P</= 0.05, regression analysis, ANOVA). Low oxygen perfusion was associated with an increase in CRH secretion into the maternal but not fetal circulation. CRH release into either the maternal or fetal circulations of abnormal placentae were not significantly different from normal controls. In conclusion CRH-induced vasodilatation of the fetal placental vasculature in vitro is inhibited during low oxygen perfusion. This effect may be related to reduced NO production. Reduced CRH induced vasodilation is associated with increased secretion of the CRH into the maternal but not fetal circulation.

Oral administration of a corticotropin-releasing hormone receptor antagonist significantly attenuates behavioral, neuroendocrine, and autonomic responses to stress in primates

We evaluated the effects of the lipophilic nonpeptide corticotropin-releasing hormone (CRH) type 1 receptor antagonist antalarmin on the behavioral, neuroendocrine, and autonomic components of the stress response in adult male rhesus macaques. After oral administration, significant antalarmin concentrations were detected in the systemic circulation and the cerebrospinal fluid by a mass spectrometry-gas chromatography assay developed specifically for this purpose. Pharmacokinetic and dose-response studies suggested that an oral dose of 20 mg/kg was optimal for behavioral and endocrine effects. We then administered this dose in a double-blind, placebo-controlled fashion to monkeys exposed to an intense social stressor: namely, placement of two unfamiliar males in adjacent cages separated only by a transparent Plexiglas screen. Antalarmin significantly inhibited a repertoire of behaviors associated with anxiety and fear such as body tremors, grimacing, teeth gnashing, urination, and defecation. In contrast, antalarmin increased exploratory and sexual behaviors that are normally suppressed during stress. Moreover, antalarmin significantly diminished the increases in cerebrospinal fluid CRH as well as the pituitary-adrenal, sympathetic, and adrenal medullary responses to stress. We conclude that CRH plays a broad role in the physiological responses to psychological stress in primates and that a CRH type 1 receptor antagonist may be of therapeutic value in human psychiatric, reproductive, and cardiovascular disorders associated with CRH system hyperactivity.

Effects of gonadotropin-releasing hormones, corticotropin-releasing hormone, and vasopressin on female sexual behavior

The effects of intracerebroventricular (icv) infusion of four neuropeptides on female sexual behavior were examined in the female musk shrew (Suncus murinus). In the first experiment, (icv) infusion of 100 ng of the mammalian form of gonadotropin-releasing hormone (mGnRH) facilitated rapid display of receptivity. Gonadotropin-releasing hormone-infused females had shorter latencies to rump present and tail wag, compared with controls. In a second experiment, icv administration of the other form of GnRH present in musk shrew brain, the chicken GnRH-II form, produced no changes in female behavior relative to the control condition. In Experiment 3, icv delivery of corticotropin-releasing hormone (CRH) facilitated female sexual behavior, relative to vasopressin and controls. The females treated with CRH had shorter latencies to display rump present, tail wag, and for the receipt of the first missed intromission compared with females in the other treatment groups. Vasopressin increased female scent marking relative to that of CRH-treated females. These data indicate that neurohormones of the hypothalamic-pituitary-gonadal and the hypothalamic-pituitary-adrenal axes can facilitate reproductive behavior in S. murinus.

Estrogen stimulates a transient increase in the number of new neurons in the dentate gyrus of the adult female rat

To determine whether a sex difference exists in the production of hippocampal cells during adulthood, we examined proliferating cells and their progeny in adult rats using the thymidine analog bromodeoxyuridine (BrdU) combined with immunohistochemistry for markers of neurons and glia. Additionally, to determine whether ovarian hormones affect cell proliferation, we examined the numbers of BrdU-labeled cells at different estrous cycle stages and after ovarian steroid manipulation. Stereological analyses of the numbers of BrdU-labeled cells revealed that females produced more cells than males in the dentate gyrus but not in the subventricular zone. The production of new hippocampal cells in females appears to be affected by ovarian hormone levels; ovariectomy diminished the number of BrdU-labeled cells, an effect reversed by estrogen replacement. A natural fluctuation in cell proliferation was also noted; females produced more cells during proestrus (when estrogen levels are highest) compared with estrus and diestrus. Many of these cells acquired neuronal characteristics, including the formation of dendrites and expression of Turned-On-After-Division 64 kDa, a marker of immature granule neurons, and the calcium-binding protein calbindin, a marker of mature granule neurons. However, examination of the numbers of pyknotic cells and the numbers of BrdU-labeled cells at longer survival times revealed that many new cells in the dentate gyrus eventually degenerate. Consistently the number of labeled cells in females is no longer higher than that observed in males by 2 weeks after the last BrdU injection. These findings suggest that estrogen-enhanced cell proliferation during proestrus results in more immature neurons in the hippocampal formation of females compared with males and present the possibility that these new cells exert an important influence on hippocampal function.

Electrophysiological responses to oxytocin and ATP in monolayers of a human sweat gland cell line

It was shown that oxytocin (OT) elicits electrophysiological responses in cultured monolayers of NCL-SG3, a human immortalized sweat gland cell line. The response to OT was greater for basal applications. It was also found that monolayers respond to ATP with a transient transepithelial-potential change, with a more pronounced response to apical than to basal applications. The IC50 for the response to OT was 180 nM at room temperature. The response to OT was not due to effects of OT on vasopressin (AVP) receptors as evidenced by three tests: (a) The response was completely blocked by the selective OT-receptor antagonist [Mpa1,D-Tyr(Et)2,Thr4,Orn8]-OT (CAP) applied at equal concentrations (100-1000 nM) to that of OT. (b) The response to OT was similar to that of ionomycin (2 microM) or ATP (150 microM). In contrast, the response to AVP (500 nM) or cAMP (2 mM) were smaller and of a different time course. (c) OT increased but AVP had no effect on the intracellular free calcium. It is suggested that OT may have a role in the regulation of salt balance in sweating.

Somatostatin treatment reduces the exaggerated response of adrenocorticotropin hormone and cortisol to corticotropin-releasing hormone in polycystic ovary syndrome

OBJECTIVE

To evaluate the influence of somatostatin analogue (octreotide) in the function of hypothalamic-pituitary-adrenal (HPA) axis in women with polycystic ovary syndrome (PCOS).

SETTING

Women referred to the Department of Obstetrics and Gynecology, Università Cattolica del Sacro Cuore.

PATIENT(S)

Twelve PCOS women and 12 normo-ovulatory controls.

INTERVENTION(S)

In early follicular phase, I microgram/kg human corticotrophin-releasing hormone (CRH) was injected at 9:00 A.M. and blood samples were collected for 90 minutes after stimulus; ACTH and cortisol plasma levels were measured. The following day at 8:00 A.M., PCOS patients received an ACTH test (250 micrograms IV) and samples were collected 60 minutes after injection. After 6 weeks of octreotide treatment (100 mg s.c. twice daily), PCOS patients repeated the same study.

MAIN OUTCOME MEASURE(S)

Plasma cortisol and ACTH concentrations.

RESULT(S)

The ACTH and cortisol baseline levels were similar in PCOS and control patients. The responses to human CRH of ACTH (incremental area = 437.86 +/- 188.7 versus 175.78 +/- 87.6 pmol/L; mean +/- SD) and cortisol (incremental area = 17,293.6 +/- 4,320.3 versus 5,885 (912.1 nmol/L) were significantly greater in PCOS with respect to control subjects. After octreotide treatment, ACTH response significantly decreased and no difference was observed with respect to controls (incremental area = 176.94 +/- 91.4). Cortisol responses were decreased by treatment. However, they remained significantly higher than in controls. Treatment did not modify adrenal response to IV ACTH.

CONCLUSION(S)

Data suggest that, in the HPA axis, hyperfunction of PCOS somatostatin could be involved partially.

Elevation of plasma beta-endorphin levels of shy elderly in response to novel laboratory experiences

Heightened psychophysiological reactivity to the novel or unfamiliar is a leading characteristic of sky or behaviorally inhibited individuals. To assess one aspect of the physiological stress response in shyness, the authors compared the morning plasma beta-endorphin levels of 15 extremely sky, healthy elderly individuals with beta-endorphin levels of 15 extremely outgoing persons on three pairs of 2 successive days. The primary finding was that sky participants exhibited significantly higher levels of beta-endorphin on the 1st days of each pair of days, compared with the 2nd days in the laboratory. No main effect for shyness or interaction between shyness and diet on endorphin levels was found. The findings are consistent with a peripheral opioid hyperreactivity to novelty in shy elderly persons. Shyness may constitute a risk factor for panic disorder in younger adults and for nasal allergies and certain cancers in older adults. Experimental design and interpretation of future studies of shy individuals' stress responses may need to consider novelty versus familiarity of the procedures and setting.

Ascorbic acid augments the adenylyl cyclase-cAMP system mediated POMC mRNA expression and beta-endorphin secretion from hypothalamic neurons in culture

Besides acting as an important cofactor in the biosynthesis of catecholamine, ascorbic acid (AA) also modulates the activity of peptidylglycine-alpha-amidating monooxygenase for the post-translational modification of neuropeptides such as alpha-MSH and TRH. We report here a novel action of AA in modulating the secretion of immunoreactive beta-endorphin (ir-beta EP) and mRNA expression of proopiomelanocortin (POMC) following the activation of cAMP-dependent protein kinase A pathway in rat hypothalamic neurons. Primary cultures of hypothalamic neurons from neonatal rats as previously described were employed in the present studies. Six days after plating, cultures were replenished with serum-free media and incubated with vehicle or various doses of AA in the presence or absence of forskolin, 3-isobutyl-1-methylxanthine (IBMX), N6,2'-O-dibutyryladenosine 3'5'-(cyclic)monophosphate [(Bu)2cAMP]. Whereas the basal ir-beta EP release was 22.0 +/- 0.4 pg/well (mean +/- S.E.; n = 3), 10 microM of forskolin treatment increased ir-beta EP release approximately 4.2-fold. Co-incubation with AA enhanced forskolin induced ir-beta EP release and that this enhancing effect of AA was both time related and dose-dependent, with an ED50 of approximately 10 microM and an Emax of 100 microM. At the concentration of 10 microM, AA augmented ir-beta EP release approximately 6.1-fold that of cultures treated with forskolin alone. A similar potentiating effect of AA was also seen in cultures co-treated with IBMX or with (Bu)2cAMP. These enhancing effects of AA were similarly found in the abundance of total cAMP and of POMC mRNA of cultures which received identical treatments. However, it is important to point out that AA alone did not modulate ir-beta EP release or the abundance of POMC mRNA or total cAMP levels of the hypothalamic cultures when protein kinase A pathway was not activated. We thus conclude that AA augments cAMP-dependent protein kinase A pathway-induced production and release of beta EP from rat hypothalamic neurons in culture. Furthermore, this biological effect of AA is, at least in part, mediated through enhancing the responsiveness of the adenylyl cyclase-cAMP system.

Neuroendocrine ageing

Ageing is followed by an involution of neuroendocrine functions, resulting in a decreased secretion of sex steroids and growth hormone. In addition, cortisol secretion may be inadequately elevated upon stress challenges, due to deficient braking functions by central glucocorticoid receptors. In combination, these endocrine perturbations will probably result in changes in psychological factors such as energy and well-being, altered body composition, and insulin resistance, as well as other risk factors for diseases characteristic of the ageing human, such as cardiovascular disease, non-insulin-dependent diabetes mellitus and stroke. This cluster of phenomena is frequently seen before the period of normal ageing, indicating premature ageing processes. The background factors in these conditions probably include psychosocial stressors, which are perceived differently depending on individual coping abilities. Socio-economic and other environmental factors, such as smoking and alcohol abuse, may well be responsible for the expression of this syndrome of premature ageing. Preventive and therapeutic trials with hormonal substitution therapy to treat these aberrations have been promising, and encourage further studies aimed at elucidating potential risks in relation to potential improvement of quality of life and, perhaps, longevity.

Glutamate enhances the adenylyl cyclase-cAMP system-induced beta-endorphin secretion and POMC mRNA expression in rat hypothalamic neurons in culture: NMDA receptor-mediated modulation

L-Glutamate, a major excitatory amino acid of the central nervous system, plays important roles as neurotransmitter and neuromodulator in the brain. Increasing evidence suggests that glutamate may also involve in the regulation of the neuroendocrine system at the hypothalamus. Employing long term monolayer hypothalamic cell cultures prepared from neonatal rats, we reported here that whereas glutamate significantly enhanced forskolin-, or N6,2'-O-dibutyryladenosine-3'5'-cyclic monophosphate [(Bu)2cAMP]-stimulated immunoreactive (ir)-beta EP release from cultures treated daily for 4 consecutive days, the excitatory amino acid alone produced little effect. This potentiation of glutamate was time-related and dose-dependent with an Emax value of the amino acid being approximately 50 microM; at this concentration glutamate augmented ir-beta EP secretion about 1.8 times (P < 0.05) that induced by 2 microM forskolin alone. Similar effects were also observed for POMC mRNA levels in cultures subjected to 6 h of the above treatment regime. This potentiating effect of glutamate appears to be mediated specifically through NMDA receptor as it can be mimicked by NMDA but not by kainic acid or quisqualic acid, and blocked by the NMDA receptor antagonist 2-amino-5-phosphonovalerate (APV), but not by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-NMDA glutamate receptor antagonist. Interestingly, glutamate was found not to enhance high doses of forskolin (10 microM) or (Bu)2cAMP (100 microM) stimulated beta EP release and POMC mRNA levels in hypothalamic cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

The potential for oxytocin (OT) to prevent breast cancer: a hypothesis

This hypothesis proposes that carcinogens in the breast are generated by the action of superoxide free radicals released when acinal gland distension, under the influence of unopposed prolactin, causes microvessel ischaemia. Inadequate nipple care in the at-risk years leads to ductal obstruction preventing the elimination of carcinogens from the breast. The regular production of oxytocin (OT) from nipple stimulation would cause contraction of the myoepithelial cells, relieving acinal gland distension and aiding the active elimination of carcinogenic fluid from the breast. Mechanical breast pump stimulation causes an increase in plasma OT levels in the luteal but not in the follicular phase of the menstrual cycle. OT production upon nipple stimulation in the luteal phase of premenopausal, non-lactating women may be protective against the high rates of mitotic breast cell division noted at this time via the potential to block the effect of oestrogen. The epidemiology of breast cancer suggests that lengthy lactation time is beneficial. Sexual activity in nulliparous women also protects and OT levels have been shown to rise with orgasm in women and in men. OT systems in the brain are intricately linked to oestrogen and progesterone levels, and it is possible that these hormones may modify the OT secretory response both centrally and through an effect on the sensitivity of the breast. OT production with nipple care and in sex and lactation, and the reduction in cycling ovarian hormones that occurs with pregnancy, may all be important preventative factors in the development of breast cancer both pre- and post-menopausally.

Corticotropin-releasing hormone induces an exaggerated response of adrenocorticotropic hormone and cortisol in polycystic ovary syndrome

OBJECTIVE

To evaluate pituitary-adrenal responsive to corticotropin-releasing hormone (CRH) stimulus in polycystic ovary syndrome (PCOS).

DESIGN

Controlled clinical study.

PATIENTS

Twelve women aged 17 to 32 years, who had been diagnosed as having PCOS, were studied. Fifteen appropriately age- and weight-matched ovulatory patients served as the control.

INTERVENTION

In the early follicular phase or after progestin-induced menses, human CRH was injected at 8:00 A.M. and blood samples were collected at 0, 15, 30, 60, and 90 minutes after stimulus. Plasma levels of ACTH and cortisol were measured.

RESULTS

Baseline levels of ACTH and cortisol were similar in PCOS and control patients. Both ACTH and cortisol response to CRH were markedly greater in the PCOS population as compared with controls. Moreover, ACTH- and cortisol-stimulated secretion was prolonged for the whole period of the study in hyperandrogenic patients with respect to controls, where baseline levels were attained 60 minutes after the stimulus.

CONCLUSIONS

Our results are consistent with the hypothesis that women with PCOS may demonstrate hyperfunction of the hypothalamic-pituitary-adrenal axis, which may be involved in the physiopathologic events leading to the complexity of the syndrome.

Opioid precursor gene expression in the human hypothalamus

Using in situ hybridization histochemistry, we studied the distribution of neurons that express preproopiomelanocortin (pre-POMC), preprodynorphin (pre-PDYN), and preproenkephalin (pre-PENK) gene transcripts within the human hypothalamus and surrounding structures. Of the three opioid systems, pre-POMC neurons have the most restricted distribution. Pre-POMC cells are most numerous in the infundibular nucleus and retrochiasmatic area of the mediobasal hypothalamus; a few labeled cells are present within the boundaries of the ventromedial nucleus and infundibular stalk. Pre-POMC message was not found in the limited samples of structures adjacent to the hypothalamus. In contrast to neurons that express pre-POMC, neurons expressing pre-PDYN and pre-PENK are more widely represented throughout the hypothalamus and extrahypothalamic structures. However, pre-PDYN and pre-PENK cells differ from one another in distribution. Pre-PDYN message is especially abundant in neurons of the tuberal and mammillary regions, with a distinct population of labeled cells in the premammillary nucleus and dorsal posterior hypothalamus. Pre-PDYN gene expression also is found in neurons of the dorsomedial nucleus, ventromedial nucleus, caudal magnocellular portion of the paraventricular nucleus, dorsolateral supraoptic nucleus, tuberomammillary nucleus, caudal lateral hypothalamus, and retrochiasmatic area. In structures immediately adjacent to the hypothalamus, pre-PDYN neurons were observed in the caudate nucleus, putamen, cortical nucleus of the amygdala, and bed nucleus of the stria terminalis. Pre-PENK neurons occur in varying numbers in all hypothalamic nuclei except the mammillary bodies. The chiasmatic region is particularly rich in pre-PENK neurons, with the highest packing density in the intermediate nucleus [the intermediate nucleus (Braak and Braak [1987] Anat. Embryol. 176:315-330) has also been termed the sexually dimorphic nucleus of the preoptic area (SDA-POA; Swaab and Fliers [1985] Science 228:1112-1115) or the interstitial nucleus of the anterior hypothalamus 1 (Allen et al. [1989] J. Neurosci. 9:497-506)], dorsal suprachiasmatic nucleus, medial preoptic area, and rostral lateral hypothalamic area. Pre-PENK neurons are numerous in the infundibular nucleus, ventromedial nucleus, dorsomedial nucleus, caudal parvicellular portion of the paraventricular nucleus, tuberomammillary nucleus, lateral hypothalamus, and retrochiasmatic area. Only a few lightly labeled cells were found in the periphery of the supraoptic nucleus and lateral tuberal nucleus. In areas adjacent to the hypothalamus, cells that contain pre-PENK message occur in the nucleus basalis of Meynert, central nucleus of amygdala, bed nucleus of the stria terminalis, caudate nucleus, and putamen.(ABSTRACT TRUNCATED AT 400 WORDS)

Relationship of anxiety, stress, and psychosocial development to reproductive health

In this review of articles on prenatal stress, anxiety, development, and reproductive health outcomes in pregnancy, the focus is on recent research in which the relationships among the major types of stressors, anxiety, and development, on the one hand, and maternal, fetal, and neonatal problems or complications, on the other hand, were examined. Available and effective treatment measures, although limited, are introduced and discussed at length in a follow-up article. Recommendations for policy development based on current research and treatment methods and directions for future research and treatment studies are presented in a third article.

Endogenous opioid peptide level changes under electrostimulation and their assessment by the EEG

Endogenous opioid peptide (EOP) system plays an important role in the interaction of human organism with different stress factors, providing stress-limiting and stress-protective functions. Different kinds of electrostimulation seem to produce anti-stress and pain relief effects due to EOP system activation. The presented paper reviews recent literature concerning EOP system activation under electrostimulation and its reflections in the EEG characteristics. The results and opportunities of high resolution EEG structure analysis utilization for EOP level control, as well as for stress-induced state assessment and correction via resonance activation of brain EEG oscillators by means of frequency-tuned external stimulation are presented.

Glucocorticoids potentiate the adenylyl cyclase-cAMP system mediated immunoreactive beta-endorphin production and secretion from hypothalamic neurons in culture

Beta-endorphin(beta EP)1-31, a potent opioid peptide of proopiomelanocortin (POMC) derivatives, is produced and released from neurons at arcuate nuclei of the rat hypothalamus. Although dexamethasone (DM) suppresses the production and secretion of POMC related peptides from rat pituitary corticotrophs, the effect of glucocorticoids on the function of hypothalamic beta EP neurons remains unclear. Employing long term monolayer cultures of neonatal rat hypothalamic cells, we report here that 4 day treatment with 10 microM of forskolin increased ir-beta EP levels in cell content and culture media by approximately 1.7 (P < 0.05) and 4.1 times (P < 0.01) above vehicle treated control cultures (mean +/- S.E.M., 47.3 +/- 2.6 pg/well and 40.4 +/- 3.0 pg/well; n = 3) respectively. Although 4 day treatment with DM alone had little effect on the release and the cell content of ir-beta EP, it significantly enhanced forskolin-induced elevation of ir-beta EP levels in cell content and in culture media. The effect of DM was dose-related and time-dependent, with an EC50 of about 1 nM; at this concentration DM enhanced ir-beta EP secretion about 2.1 times (P < 0.01) above that induced by 10 microM of forskolin alone. Furthermore, the potentiating effect of DM was specifically suppressed by 100 nM of RU38486 (P < 0.01), a glucocorticoid receptor antagonist, but not by an equivalent dose of RU28318, a mineralocorticoid receptor antagonist. In addition, Northern blot analysis showed that forskolin (10 microM) increased the abundance of POMC mRNA 1.4 fold above that of vehicle treated control cultures. Whereas by itself, DM (10 nM) had little effect on the level of POMC mRNA, it enhanced forskolin-stimulated increase of the abundance of POMC mRNA approximately 2.6 times. Moreover, DM also augmented 1.6 times (P < 0.05) forskolin-induced but not 3-isobutyl-1-methylxanthine (IBMX)-induced increase of cAMP production (5.5 +/- 0.4 pmol/well; mean +/- S.E.M., n = 3) in the cultures. Taken together, our findings suggest that in contrast to the inhibitory effect on pituitary corticotrophs, glucocorticoids enhance the production and secretion of beta EP from rat hypothalamic neurons by facilitating the stimulatory effect mediated, in part, through the adenylyl cyclase-cAMP system.

Buprenorphine: dose-related effects on cocaine and opioid use in cocaine-abusing opioid-dependent humans

Fifteen subjects dependent on both opioids and cocaine completed an ascending and tapering schedule of buprenorphine dosing, with maintenance for 21 days at each dose of buprenorphine (4, 8, 12, 16 mg sublingual daily) during both ascending and tapering phases. Higher doses of buprenorphine led to greater reductions in opioid use: 64.7% of subjects were opioid abstinent for 3 weeks at the 16-mg dose compared to 27.3% at the 4-mg ascending dose. The proportion of cocaine-positive urine toxicologies was significantly lower during buprenorphine tapering (12 mg, 8 mg, 4 mg) compared to ascending doses up to 8 mg, with intermediate results at 12 mg and 16 mg during the ascending phase (F value = 6.6, df = 8,813, p < 0.001). Self-reported days, times, and quantity of cocaine used per week showed a similar pattern of intermediate reductions at the 12-mg and 16-mg dose during the ascending phase and significantly reduced values during the descending schedule. There were no significant buprenorphine dose effects on cocaine euphoria. This study indicates that buprenorphine dose has a significant and substantial impact on opioid use and a significant but less robust impact on cocaine use, with higher doses and longer time on buprenorphine leading to attenuated cocaine use.