Cold stress induces metabolic activation of thyrotrophin-releasing hormone-synthesising neurones in the magnocellular division of the hypothalamic paraventricular nucleus and concomitantly changes ovarian sympathetic activity parameters

Multi-Organ Increase in Norepinephrine Levels after Central Leptin Administration and Diet-Induced Obesity

Autonomic innervation is important to regulate homeostasis in every organ of the body. The sympathetic nervous system controls several organs associated with metabolism and reproduction, including adipose tissue, the liver, and the ovaries. The sympathetic nervous system is controlled within the central nervous system by neurons located in the hypothalamus, which in turn are regulated by hormones like leptin. Leptin action in the hypothalamus leads to increased sympathetic activity in the adipose tissue. In this short report, we propose that leptin action in the brain also controls the sympathetic innervation of other organs like the liver and the ovary. We performed two experiments: We performed an intracerebroventricular (ICV) injection of leptin and measured norepinephrine levels in several organs, and we used a validated model of overnutrition and obesity to evaluate whether an increase in leptin levels coexists with high levels of norepinephrine in the liver and ovaries. Norepinephrine was measured by ELISA in adipose tissue and by HPLC-EC in other tissues. Leptin was measured by ELISA. We found that the ICV injection of leptin increases norepinephrine levels in several organs, including the liver and ovaries. Also, we found that diet-induced obesity leads to an increase in leptin levels while inducing an increase in norepinephrine levels in the liver and ovaries. Finally, since hyperactivity of the sympathetic nervous system is observed both in non-alcoholic fatty liver disease and polycystic ovary syndrome, we think that an increase in norepinephrine levels induced by hyperleptinemia could be involved in the pathogenesis of both diseases.

Allostasis in Neuroendocrine Systems Controlling Reproduction

Allostasis provides a supporting role to the homeostatic control of biological variables in mammalian species. While the concept of homeostasis is related to the control of variables within a set point or range that are essential to life, allostasis refers to systems that facilitate adaptation to challenges that the organism faces and the new requirements for survival. Essential for such adaptation is the role played by the brain in eliciting neural and neuroendocrine responses. Reproductive function is fundamental for the survival of species but is costly in energetic terms and requires a synchrony with an ever-changing environment. Thus, in many species reproductive function is blocked or delayed over immediate challenges. This review will cover the physiological systems and neuroendocrine pathways that supply allostatic control over reproductive neuroendocrine systems. Light, hypoxia, temperature, nutrition, psychosocial, and immune mediators influence the neuroendocrine control of reproductive functions through pathways that are confluent at the paraventricular nucleus; however, understanding of the integrative responses to these stimuli has not been clarified. Likely, the ultimate consequence of these allostatic mechanisms is the modification of kisspeptin and gonadotropin-releasing hormone neuronal activity, thus compromising reproduction function in the short term, while preserving species survivability.

Gestational Sympathetic Stress Programs the Fertility of Offspring: A Rat Multi-Generation Study

The exposure to sympathetic stress during the entire period of gestation (4 °C/3 h/day) strongly affects the postnatal reproductive performance of the first generation of female offspring and their fertility capacity. The aim of this work was to determine whether this exposure to sympathetic stress affects the reproductive capacity of the next three generations of female offspring as adults. Adult female Sprague–Dawley rats were mated with males of proven fertility. We studied the reproductive capacity of the second, third, and fourth generations of female offspring (the percentage of pregnancy and the number and weight of female offspring). The estrus cycle activity of the progenies was studied, and a morphological analysis of the ovaries was carried out to study the follicular population. The second generation had a lower number of pups per litter and a 20% decrease in fertile capacity. The estrus cycle activity of the third generation decreased even more, and they had a 50% decrease in their fertile capacity, and their ovaries presented polycystic morphology. The fourth generation however, recovered their reproductive capacity but not the amount of newborns pups. Most probably, the chronic intrauterine exposure to the sympathetic stress programs the female gonads to be stressed in a stressful environment; since the fourth generation was the first born with no direct exposure to stress during development, it opens studies on intrauterine factors affecting early follicular development.

New method of FACS analyzing and sorting of intact whole ovarian fragments (COPAS) after long time (24 h) cooling to 5 °C before cryopreservation

As recently announced by the American Society for Reproductive Medicine (ASRM), human ovarian tissue cryopreservation is an established option for fertility preservation in prepubertal girls and young women undergoing gonadotoxic treatments for cancer as well as some autoimmune diseases. Proper ovarian tissue assessment before and after cryopreservation is essential to increase success rates. Ovarian fragments from 16 patients were divided into small pieces in form of cortex with medulla, and randomly divided into the following two groups. Pieces of Group 1 (n = 16) were frozen immediately after operation, thawed and just after thawing their quality was analyzed. Group 2 pieces (n = 16) after operation were cooled to 5 °C for 24 h, then frozen after 24 h pre-cooling to 5 °C, thawed and just after thawing their quality was analyzed. The effectiveness of the pre-freezing cooling of tissue was evaluated by the development and viability of follicles (Calcein-AM and Propidium Iodide) using complex object parametric analyzer and sorter machine (COPAS). Positive effect of cooling of cells to low supra-zero temperatures on their future development after re-warming has been observed. New flow cytometry- technique is suitable for the evaluation and sorting of cryopreserved whole human whole intact ovarian fragments. Long time (24 h) cooling of ovarian tissue to 5 °C before cryopreservation has a trend of a cell viability increasing.

Huperzine-A administration recovers rat ovary function after sympathetic stress

Chronic cold stress affects ovarian morphology and impairs fertility in rats. It causes an ovarian polycystic ovary (PCOS)-like phenotype, which resembles PCOS in women. The mechanism of cold stress action involves increased ovarian noradrenaline (NA) levels, which remain elevated after cessation of cold stress. By contrast, ovarian acetylcholine (ACh) levels are only transiently elevated and returned to control levels after a 28-day post stress period. Because ACh can exert trophic actions in the ovary, we hypothesised that a sustained elevation of ovarian ACh levels by intraovarian exposure to the ACh-esterase blocker huperzine-A (Hup-A) may interfere with cold stress-induced ovarian changes. This possibility was examined in female Sprague-Dawley rats exposed to cold stress (4°C for 3 h day^-1 for 28 days), followed by a 28-day period without stress. To elevate ACh, in a second group Hup-A was delivered into the ovary of cold stress-exposed rats. A third group was not exposed to cold stress. As expected, cold stress elevated ovarian NA, reduced the number of corpora lutea and increased the number of follicular cysts. It increased plasma testosterone and oestradiol but decreased plasma levels of progesterone. In the Hup-A group, ovarian levels of both, NA and ACh, were elevated, there were fewer cysts and normal testosterone and oestradiol plasma levels were found. However, progesterone levels remained low. Most likely, low progesterone was associated with impaired mating behaviour and low pregnancy rate. We propose that elevated intraovarian levels of ACh are involved in the rescue of ovarian function, opening a target to control ovarian diseases affecting follicular development.

Central Ceramide Signaling Mediates Obesity-Induced Precocious Puberty

Childhood obesity, especially in girls, is frequently bound to earlier puberty, which is linked to higher disease burden later in life. The mechanisms underlying this association remain elusive. Here we show that brain ceramides participate in the control of female puberty and contribute to its alteration in early-onset obesity in rats. Postnatal overweight caused earlier puberty and increased hypothalamic ceramide content, while pharmacological activation of ceramide synthesis mimicked the pubertal advancement caused by obesity, specifically in females. Conversely, central blockade of de novo ceramide synthesis delayed puberty and prevented the effects of the puberty-activating signal, kisspeptin. This phenomenon seemingly involves a circuit encompassing the paraventricular nucleus (PVN) and ovarian sympathetic innervation. Early-onset obesity enhanced PVN expression of SPTLC1, a key enzyme for ceramide synthesis, and advanced the maturation of the ovarian noradrenergic system. In turn, obesity-induced pubertal precocity was reversed by virogenetic suppression of SPTLC1 in the PVN. Our data unveil a pathway, linking kisspeptin, PVN ceramides, and sympathetic ovarian innervation, as key for obesity-induced pubertal precocity.

Evidence of metabolic activity during low-temperature ovarian tissue preservation in different media

PURPOSE

Although ovarian tissue transportation has been validated for up to 24 h, there is no standard protocol to date. We aimed to elucidate how existing media currently used for ovarian tissue transportation affect ovarian tissue metabolism and cell viability.

METHODS

Cow ovarian fragments were immersed in 0.9% NaCl solution, IVF medium, Leibovitz 15 medium (L-15), or PBS for 1, 4, or 24 h at 4 °C. Media were analyzed for pH, lactate dehydrogenase (LDH) activity, and glucose, pyruvate, and lactate concentrations, while apoptosis was assessed by TUNEL assays in fixed fragments. Viability rates were assessed by flow cytometry (FACS).

RESULTS

There were lower pH levels in NaCl at all time points compared with other media. LDH activity increased with time and was lowest in NaCl at 1 and 4 h. There was no significant difference in glucose levels, but a significant pyruvate decrease in L-15 and a significant lactate increase in all media. TUNEL showed apoptosis rates ranging from 0 to 5%. FACS showed a mean of 4% necrotic cells and 15-19% apoptotic cells after 1 h of incubation, but less than 1% necrotic cells and 2-6% apoptotic cells after 24 h in all media.

CONCLUSION

Our results indicate marked metabolic activity in ovarian tissue at 4 °C and suggest that cells use internal sources of energy, which may influence transplantation outcomes. This highlights the importance of better understanding whole tissue dynamics to develop a standard protocol for ovarian tissue transportation. Graphical abstract.

Effect of cold stress on ovarian & uterine microcirculation in rats and the role of endothelin system

BACKGROUND

Cold, an environmental factor, induces many reproductive diseases. It is known that endothelin (ET) is a potent vasoconstrictor, and cold stress can increase the expression of ET and its receptors. The cold stress rat model was developed to examine two parameters: (1) the effects of cold stress on ovarian and uterine morphology, function, and microvascular circulation and (2) possible mechanisms of ET and its receptors involved in cold stress-induced menstruation disorders.

METHODS

The rat cold stress model was prepared with an ice water bath. The estrous cycle was observed by methylene blue and hematoxylin and eosin (H&E) staining. Serum estradiol 2 (E₂), testosterone (T), progesterone (P) were detected by radioimmunoassay. Hemorheology indices were measured. The real-time blood flow of auricle and uterine surfaces was measured. Expressions of CD34 and α-SMA in ovarian and uterine tissues were detected by immunohistochemistry. ET-1 contents in serum were tested, and expressions of ET-receptor types A and B (ET-AR and ET-BR) in ovarian tissues were detected via Western blotting.

RESULTS

Cold stress extended the estrous cycle, thereby causing reproductive hormone disorder, imbalance of local endothelin/nitric oxide expression, and microcirculation disturbance. Cold-stress led to up-regulation of ET-AR expression and protein and down-regulation of ET-BR expression in rats.

CONCLUSIONS

This study suggests that the reason for cold stress-induced dysfunction in reproductive organs may be closely related to the imbalance of ET-1 and its receptor expressions, leading to microvascular circulation disorders in local tissues.

TRH Neurons and Thyroid Hormone Coordinate the Hypothalamic Response to Cold

Thyroid hormone (TH) plays a key role in regulating body temperature in mammals. Cold exposure stimulates the hypothalamus-pituitary-thyroid (HPT) axis at the hypothalamic level by activating hypophysiotropic thyrotropin-releasing hormone (TRH)-producing neurons, ultimately resulting in increased plasma TH concentrations. Importantly, the local TH metabolism within various cold-responsive organs enables tissue-specific action of TH on heat production and adaption to cold independently of the circulating TH levels. In addition to these neuroendocrine effects, TRH neurons in the hypothalamus also have neural connections with brown adipose tissue (BAT), probably contributing to regulation of thermogenesis by the autonomic nervous system. Recent studies have demonstrated that intrahypothalamic TH has profound metabolic effects on BAT, the liver, and the heart that are mediated via the autonomic nervous system. These effects originate in various hypothalamic nuclei, including the paraventricular nucleus (PVN), the ventromedial nucleus, and recently reported neurons in the anterior hypothalamic area, indicating a potential central function for TH on thermoregulation. Finally, although robust stimulation of the thermogenic program in BAT was shown upon TH administration in the ventromedial hypothalamus, the physiological relevance of these neurally mediated effects of TH is unclear at present. This review provides an overview of studies reporting the role of TH in cold defense, with a focus on recent literature evidencing the centrally mediated effects of TRH and TH.

Inspiratory-Activated Airway Vagal Preganglionic Neurones Excited by Thyrotropin-Releasing Hormone via Multiple Mechanisms in Neonatal Rats

The airway vagal preganglionic neurons (AVPNs) providing projections to intrinsic tracheobronchial ganglia are considered to be crucial to modulation of airway resistance in physiological and pathological states. AVPNs classified into inspiratory-activated AVPNs (IA-AVPNs) and inspiratory-inhibited AVPNs (II-AVPNs) are regulated by thyrotropin-releasing hormone (TRH)-containing terminals. TRH causes a direct excitatory current and attenuates the phasic inspiratory glycinergic inputs in II-AVPNs, however, whether and how TRH influences IA-AVPNs remains unknown. In current study, TRH regulation of IA-AVPNs and its mechanisms involved were investigated. Using retrogradely fluorescent labeling method and electrophysiology techniques to identify IA-AVPNs in brainstem slices with rhythmic inspiratory hypoglossal bursts recorded by a suction electrode, the modulation of TRH was observed with patch-clamp technique. The findings demonstrate that under voltage clamp configuration, TRH (100 nM) caused a slow excitatory inward current, augmented the excitatory synaptic inputs, progressively suppressed the inhibitory synaptic inputs and elicited a distinctive electrical oscillatory pattern (OP). Such a current and an OP was independent of presynaptic inputs. Carbenoxolone (100 μM), a widely used gap junction inhibitor, fully suppressed the OP with persistence of TRH-induced excitatory slow inward current and augment of the excitatory synaptic inputs. Both tetrodotoxin (1 μM) and riluzole (20 μM) functioned to block the majority of the slow excitatory inward current and prevent the OP, respectively. Under current clamp recording, TRH caused a slowly developing depolarization and continuously progressive oscillatory firing pattern sensitive to TTX. TRH increased the firing frequency in response to injection of a square-wave current. The results suggest that TRH excited IA-AVPNs via the following multiple mechanisms: (1) TRH enhances the excitatory and depresses the inhibitory inputs; (2) TRH induces an excitatory postsynaptic slow inward current; (3) TRH evokes a distinctive OP mediated by gap junction.

High salt intake enhances swim stress-induced PVN vasopressin cell activation and active stress coping

PURPOSE

Stress contributes to many psychiatric disorders; however, responsivity to stressors can vary depending on previous or current stress exposure. Relatively innocuous heterotypic (differing in type) stressors can summate to result in exaggerated neuronal and behavioral responses. Here we investigated the ability of prior high dietary sodium chloride (salt) intake, a dehydrating osmotic stressor, to enhance neuronal and behavioral responses of mice to an acute psychogenic swim stress (SS). Further, we evaluated the contribution of the osmo-regulatory stress-related neuropeptide arginine vasopressin (VP) in the hypothalamic paraventricular nucleus (PVN), one of only a few brain regions that synthesize VP. The purpose of this study was to determine the impact of high dietary salt intake on responsivity to heterotypic stress and the potential contribution of VPergic-mediated neuronal activity on high salt-induced stress modulation, thereby providing insight into how dietary (homeostatic) and environmental (psychogenic) stressors might interact to facilitate psychiatric disorder vulnerability.

APPROACH

Salt loading (SL) with 4% saline for 7 days was used to dehydrate and osmotically stress mice prior to exposure to an acute SS. Fluid intake and hematological measurements were taken to quantify osmotic dehydration, and serum corticosterone levels were measured to index stress axis activation. Immunohistochemistry (IHC) was used to stain for the immediate early gene product c-Fos to quantify effects of SL on SS-induced activation of neurons in the PVN and extended amygdala - brain regions that are synaptically connected and implicated in responding to osmotic stress and in modulation of SS behavior, respectively. Lastly, the role of VPergic PVN neurons and VP type 1 receptor (V1R) activity in the amygdala in mediating effects of SL on SS behavior was evaluated by quantifying c-Fos activation of VPergic PVN neurons and, in functional experiments, by nano-injecting the V1R selective antagonist dGly[Phaa1,d-tyr(et), Lys, Arg]-VP bilaterally into the amygdala prior to the SS.

FINDINGS

SL increased serum osmolality (P < 0.01), which positively correlated with time spent mobile during, and time spent grooming after a SS (P < 0.01, P < 0.01), and SL increased serum corticosterone levels (P < 0.01). SL alone increased c-Fos immunoreactivity among PVN neurons (P = .02), including VP positive neurons (P < 0.01). SL increased SS-induced c-Fos activation of PVN neurons as well (P < 0.01). In addition, SL and SS each increased the total number of PVN neurons that were immunoreactive for VP (P < 0.01). An enhancing effect of SL and SS was observed on c-Fos positive cell counts in the central (P = .02) and basolateral (P < 0.01) nuclei of the amygdala and bilateral nano-injections of V1R antagonist into the amygdala reduced time spent mobile both in salt loaded and control mice during SS (P < 0.05, P < 0.05).

SUMMARY

Taken together, these data indicate that neuronal and behavioral responsivity to an acute psychogenic stressor is potentiated by prior exposure to high salt intake. This synergistic effect was associated with activation of PVN VP neurons and depended, in part, on activity of V1 receptors in the amygdala. Findings provide novel insight into neural mechanisms whereby prior exposure to a homeostatic stressor such as osmotic dehydration by excessive salt intake increases responsivity to a perceived stress. These experiments show that high dietary salt can influence stress responsivity and raise the possibility that excessive salt intake could be a contributing factor in the development of stress-related psychiatric disorders.

Administration of Thyrotropin-Releasing Hormone in the Hypothalamic Paraventricular Nucleus of Male Rats Mimics the Metabolic Cold Defense Response

BACKGROUND

Cold exposure increases thyrotropin-releasing hormone (TRH) expression primarily in the hypothalamic paraventricular nucleus (PVN). The PVN is a well-known hypothalamic hub in the control of energy metabolism. TRH terminals and receptors are found on PVN neurons. We hypothesized that TRH release in the PVN plays an important role in the control of thermogenesis and energy mobilization during cold exposure.

METHODS

Male Wistar rats were exposed to a cold environment (4°C) or TRH retrodialysis in the PVN for 2 h. We compared the effects of cold exposure and TRH administration in the PVN on plasma glucose, corticosterone, and thyroid hormone concentrations, body temperature, locomotor activity, as well as metabolic gene expression in the liver and brown adipose tissue.

RESULTS

Cold exposure increased body temperature, locomotor activity, and plasma corticosterone concentrations, but blood glucose concentrations were similar to that of room temperature control animals. TRH administration in the PVN also promptly increased body temperature, locomotor activity and plasma corticosterone concentrations. However, TRH administration in the PVN markedly increased blood glucose concentrations and endogenous glucose production (EGP) compared to saline controls. Selective hepatic sympathetic or parasympathetic denervation reduced the TRH-induced increase in glucose concentrations and EGP. Gene expression data indicated increased gluconeogenesis in liver and lipolysis in brown adipose tissue, both after cold exposure and TRH administration.

CONCLUSIONS

We conclude that TRH administration in the rat PVN largely mimics the metabolic and behavioral changes induced by cold exposure indicating a potential link between TRH release in the PVN and cold defense.

A screen for modulators reveals that orexin-A rapidly stimulates thyrotropin releasing hormone expression and release in hypothalamic cell culture

In the paraventricular nucleus of the mammalian hypothalamus, hypophysiotropic thyrotropin releasing hormone (TRH) neurons integrate metabolic information and control the activity of the thyroid axis. Additional populations of TRH neurons reside in various hypothalamic areas, with poorly defined connections and functions, albeit there is evidence that some may be related to energy balance. To establish extracellular modulators of TRH hypothalamic neurons activity, we performed a screen of neurotransmitters effects in hypothalamic cultures. Cell culture conditions were chosen to facilitate the full differentiation of the TRH neurons; these conditions had permitted the characterization of the effects of known modulators of hypophysiotropic TRH neurons. The major end-point of the screen was Trh mRNA levels, since they are generally rapidly (0.5-3h) modified by synaptic inputs onto TRH neurons; in some experiments, TRH cell content or release was also analyzed. Various modulators, including histamine, serotonin, β-endorphin, met-enkephalin, and melanin concentrating hormone, had no effect. Glutamate, as well as ionotropic agonists (kainate and N-Methyl-d-aspartic acid), increased Trh mRNA levels. Baclofen, a GABA_B receptor agonist, and dopamine enhanced Trh mRNA levels. An endocannabinoid receptor 1 inverse agonist promoted TRH release. Somatostatin increased Trh mRNA levels and TRH cell content. Orexin-A rapidly increased Trh mRNA levels, TRH cell content and release, while orexin-B decreased Trh mRNA levels. These data reveal unaccounted regulators, which exert potent effects on hypothalamic TRH neurons in vitro.

Long-Time Cooling before Cryopreservation Decreased Translocation of Phosphatidylserine (Ptd-L-Ser) in Human Ovarian Tissue

Objectives

To translocation (externalization) of phosphatidylserine lead at least the five negative effects observed during cells cryopreservation: hypoxia, increasing of intracellular Ca²⁺, osmotic disruption of cellular membranes, generation of reactive oxygen species (ROS) and lipid peroxidation. The aim of this study was to test the intensiveness of the phosphatidylserine translocation immediately after thawing and after 45 d xenografting of human ovarian tissue, which was either frozen just after operative removal from patient or cooled before cryopreservation to 5°C for 24 h and then frozen.

Materials and Methods

Ovarian fragments from twelve patients were divided into small pieces in form of cortex with medulla, and randomly divided into the following four groups. Pieces of Group 1 (n=30) were frozen immediately after operation, thawed and just after thawing their quality was analyzed. Group 2 pieces (n=30) after operation were cooled to 5°C for 24 h, then frozen after 24 h pre-cooling to 5°C, thawed and just after thawing their quality was analyzed. Group 3 pieces (n=30) were frozen immediately after operation without pre-cooling, thawed, transplanted to SCID mice and then, after 45 d of culture their quality was analyzed. Group 4 pieces (n=30) were frozen after 24 h pre-cooling to 5°C, thawed, transplanted to SCID mice and then, after 45 d their quality was analyzed. The effectiveness of the pre-freezing cooling of tissuewas evaluated by the development of follicles (histology) and by intensiveness of translocation of phosphatidylserine (FACS with FITC-Annexin V and Propidium Iodide).

Results

For groups 1, 2, 3 and 4 the mean densities of follicles per 1 mm³ was 19.0, 20.2, 12.9, and 12.2, respectively (P_{1-2, 3-4} >0.1). For these groups, 99%, 98%, 88% and 90% preantral follicles, respectively were morphologically normal (P_{1-2, 3-4} >0.1). The FACS analysis showed significantly decreased intensiveness of translocation of phosphatidylserine after pre-cooling of frozen tissue (46.3% and 33.6% in Groups 2 and 4, respectively), in contrast with tissue frozen without pre-cooling (77.1% and 60.2 % in Groups 1 and 3, respectively, P_{1, 3-2, 4} <0.05).

Conclusions

Long time (24 h) cooling of ovarian tissue to 5°C before cryopreservation decreased translocation of phosphatidylserine that evidences about increases the viability of the cells in the tissue after thawing.

Stress and the reproductive axis

There exists a reciprocal relationship between the hypothalamic-pituitary-adrenal (HPA) and the hypothalamic-pituitary-gonadal (HPG) axes, wherein the activation of one affects the function of the other and vice versa. For example, both testosterone and oestrogen modulate the response of the HPA axis, whereas activation of the stress axis, especially activation that is repeating or chronic, has an inhibitory effect upon oestrogen and testosterone secretion. Alterations in maternal care can produce significant effects on both HPG and HPA physiology, as well as behaviour in the offspring at adulthood. For example, changes in reproductive behaviour induced by altered maternal care may alter the expression of sex hormone receptors such as oestrogen receptor (ER)α that govern sexual behaviour, and may be particularly important in determining the sexual strategies utilised by females. Stress in adulthood continues to mediate HPG activity in females through activation of a sympathetic neural pathway originating in the hypothalamus and releasing norepinephrine into the ovary, which produces a noncyclic anovulatory ovary that develops cysts. In the opposite direction, sex differences and sex steroid hormones regulate the HPA axis. For example, although serotonin (5-HT) has a stimulatory effect on the HPA axis in humans and rodents that is mediated by the 5-HT1A receptor, only male rodents respond to 5-HT1A antagonism to show increased corticosterone responses to stress. Furthermore, oestrogen appears to decrease 5-HT1A receptor function at presynaptic sites, yet increases 5-HT1A receptor expression at postsynaptic sites. These mechanisms could explain the heightened stress HPA axis responses in females compared to males. Studies on female rhesus macaques show that chronic stress in socially subordinate female monkeys produces a distinct behavioural phenotype that is largely unaffected by oestrogen, a hyporesponsive HPA axis that is hypersensitive to the modulating effects of oestrogen, and changes in 5-HT1A receptor binding in the hippocampus and hypothalamus of social subordinate female monkeys that are restored or inverted by oestrogen replacement. This review summarises all of these studies, emphasising the profound effect that the interaction of the reproductive and stress axes may have on human reproductive health and emotional wellbeing.

Maternal sympathetic stress impairs follicular development and puberty of the offspring

Chronic cold stress applied to adult rats activates ovarian sympathetic innervation and develops polycystic ovary (PCO) phenotype. The PCO syndrome in humans originates during early development and is expressed before or during puberty, which suggests that the condition derived from in utero exposure to neural- or metabolic-derived insults. We studied the effects of maternal sympathetic stress on the ovarian follicular development and on the onset of puberty of female offspring. Timed pregnant rats were exposed to chronic cold stress (4 °C, 3 h/daily from 1000 to 1300 h) during the entire pregnancy. Neonatal rats exposed to sympathetic stress during gestation had a lower number of primary, primordial, and secondary follicles in the ovary and a lower recruitment of primary and secondary follicles derived from the primordial follicular pool. The expression of the FSH receptor and response of the neonatal ovary to FSH were reduced. A decrease in nerve growth factor (NGF) mRNA was found without change in the low-affinity NGF receptor. The FSH-induced development of secondary follicles was decreased. At puberty, estradiol plasma levels decreased without changes in LH plasma levels. Puberty onset (as shown by the vaginal opening) was delayed. Ovarian norepinephrine (NE) was reduced; there was no change in its metabolite, 3-methoxy-4-hydroxyphenylglycol, in stressed rats and no change in NE turnover. The changes in ovarian NE in prepubertal rats stressed during gestation could represent a lower development of sympathetic nerves as a compensatory response to the chronically increased NE levels during gestation and hence participate in delaying reproductive performance in the rat.

Prenatal maternal stress exposure and immune function in the offspring

The intra-uterine environment provides the first regulatory connection for the developing fetus and shapes its physiological responses in preparation for postnatal life. Psychological stress acts as a programming determinant by setting functional parameters to abnormal levels, thus inducing postnatal maladaptation. The effects of prenatal maternal stress (PNMS) on the developing immune system have been documented mostly through animal studies, but inconsistent results and methodological differences have hampered the complete understanding of these findings. As the immune system follows a similar ontogenic pattern in all mammals, a translational framework based on the developmental windows of vulnerability proposed by immunotoxicology studies was created to integrate these findings. The objective of this review is to examine the available literature on PNMS and immune function in the offspring through the above framework and gain a better understanding of these results by elucidating the moderating influence of the stressor type, timing and duration, and the offspring species, sex and age at assessment. The evaluation of the literature through this framework showed that the effects of PNMS are parameter specific: the moderating effects of timing in gestation were relevant for lymphocyte population numbers, Natural Killer cell function and mitogen-induced proliferation. The presence of an important and directional sexual dimorphism was evident and the influence of the type or duration of PNMS paralleled that of stress in non-pregnant animals. In conclusion, PNMS is a relevant factor in the programming of immune function. Its consequences may be related to disorders with an important immune component such as allergies.

Increasing Follicular and Stromal Cell Proliferation in Cryopreserved Human Ovarian Tissue after Long-Term Precooling Prior to Freezing: In Vitro versus Chorioallantoic Membrane (CAM) Xenotransplantation

A positive effect on the future development of cells, which have been cooled to low suprazero temperatures and then thawed, has been observed before and is not new. The aim of this study was to test the effectiveness of postthawing culture of human ovarian tissue, which was either frozen just after operative removal or cooled after removal to 5°C for 24 h before cryopreservation. Ovarian fragments from six patients were divided into small pieces in the form of cortex with medulla and randomly divided into the following four groups: Group 1 consisted of pieces that just after removal had been cultured in vitro for 8 days in a big volume of medium with mechanical agitation; Group 2 included pieces cooled after operation to 5°C for 24 h and then cultured in vitro for 8 days; Group 3 was comprised of pieces frozen–thawed just after operation and then cultured for 5 days in the chorioallantoic membrane (CAM) culture system; and the pieces in Group 4 were cooled after operation to 5°C for 24 h, frozen–thawed, and then cultured in the CAM system for 5 days. The effectiveness of the tissue culture was evaluated by the development of follicles and by the intensiveness of proliferation in the tissue (by expression of cytokeratin and Ki-67). For Groups 1, 2, 3, and 4, the mean densities of follicles per 1 mm3 was 12.9, 12.2, 12.4, and 16.1, respectively ( p1–2 > 0.1; p3–4 < 0.05). For these groups, 87%, 95%, 71%, and 84% of the preantral follicles were morphologically normal ( p1–2, 3–4 < 0.05). The immunohistochemical analysis showed increased proliferation after cooling of fresh and cryopreserved tissue. Long-term (24 h) cooling of ovarian tissue to 5°C before cryopreservation increases the viability of the cells in the tissue after thawing. Additionally, the efficacy of the CAM system for the culture of thawed human ovarian tissue was demonstrated.

The Noradrenergic Innervation and Steroidogenic Activity of Porcine Cystic Ovaries

The aim of the present study was to investigate the distribution and density of noradrenergic nerve fibres (NNFs), content of catecholamines (CATs) and steroids in the cystic ovaries of gilts receiving DXM from middle luteal phase. Cystic status of ovaries was induced by i.m. DXM injections on days 7-21 of the estrous cycle. During the same time, gilts in the control group received saline. The ovaries were collected on predicted day 11 of the second studied estrous cycle. The cystic ovaries were supplied by more numerous NNFs than the control gonads. Moreover after DXM injections, the content of CATs and progesterone and androstendione (A4) in the cystic wall were elevated, while the levels of A4, testosterone and estradiol-17β in the cystic fluid were lowered. Our results show that in the porcine cystic ovaries, induced by DXM injections from middle phase of estrous cycle, increased the density of NNFs and level of CATs, and that it was accompanied by changes in the content of steroids. Moreover, this study is a further confirmation that the morphological and functional changes of cystic ovaries are partly dependent on phase of the estrous cycle in which the induction of the ovarian cysts was initiated.

Transitory activation of the central and ovarian norepinephrine systems during cold stress-induced polycystic ovary in rats

Cold stress-induced ovarian sympathetic activation is associated with the development of ovarian cysts in rats. Although we have hypothesised that polycystic ovary (PCO) features induced by cold stress, as prevented by lesion of the noradrenergic nucleus locus coeruleus (LC), were a result of the increased activity of the ovarian norepinephrine (NE) system, this was not evident after 8 weeks of stress. In the present study, we investigated the temporal changes in LC and ovarian NE activities and steroid secretion in rats exposed to single (SS) or repeated (RS) cold stress. SS and 4 week (4W)-RS but not 8 week (8W)-RS increased c-Fos expression in the LC and ovarian NE release. Plasma oestradiol, testosterone and progesterone levels tended to increase in 4W-RS and were elevated in 8W-RS rats, which displayed PCO morphology. β-adrenergic receptor agonist increased steroid hormone release from the ovary of unstressed (US) but not from 8W-RS rats. To determine whether increased activity of noradrenergic system during the initial 4 weeks of RS would be sufficient to promote PCO, rats were exposed to 4 weeks of cold stress and kept in ambient temperature for the next 4 weeks (4W-RS/4W-US). Accordingly, PCO morphology, increased steroid secretion and decreased ovulation rate were found in 4W-RS/4W-US rats, strengthening the hypothesis that the initial increase in NE release triggers the development of PCO. The correlated activity of LC neurones and ovarian noradrenergic terminals and the induction of PCO in 4W-RS/4W-US rats provide functional evidence for a major role of NE in disrupting follicular development and causing the long-lasting endocrine abnormalities found in stress-induced PCO.

Cryopreservation of Ovarian Tissue: Detailed Description of Methods for Transport, Freezing and Thawing

Purpose: In many cases cancer therapy leads to an irreversible reduction or even loss of ovarian reserve. Cryopreservation of ovarian tissue with subsequent thawing and re-transplantation of tissue after the cancer is in remission constitutes a promising method to preserve fertility in women. To date, more than 25 cases of live births after re-transplantation of cryopreserved ovarian tissue have been published worldwide. In Germany the first live birth after re-transplantation of cryopreserved tissue was in 2011. Material and Methods: After surgical removal of ovarian tissue in the Gynaecological Clinic of Dresden University, the tissue was sent to the Gynaecological Clinic of Bonn University in a special transport container at 5 °C and was frozen the next day using 1.5 M dimethyl sulfoxide cryosolution. In 2010 this ovarian tissue was thawed using a sucrose solution in the Gynaecological Clinic of Erlangen University Clinical Centre and was laparoscopically re-transplanted into the patient. Results: The patient became pregnant, the pregnancy was uneventful, and she gave birth to a healthy boy. Conclusion: Freezing of ovarian tissue with subsequent re-transplantation as described here is a viable method to preserve fertility in cancer patients.

Evidence for a celiac ganglion-ovarian kisspeptin neural network in the rat: intraovarian anti-kisspeptin delays vaginal opening and alters estrous cyclicity

Kisspeptin and its receptor GPR54 have been described as key hypothalamic components in the regulation of GnRH secretion. Kisspeptin is also present in several regions of the central nervous system and the peripheral organs and has recently been identified in the superior ganglion. Herein, we tested the possibility that ovarian kisspeptin is regulated by the sympathetic nervous system and participates locally in the regulation of ovarian function. Both ovarian and celiac ganglion kisspeptin mRNA levels increase during development, whereas kisspeptin peptide levels and plasma levels decrease during development. In the celiac ganglion, kisspeptin colocalized with tyrosine hydroxylase, indicating potential kisspeptin synthesis and transport within the sympathetic neurons. A continuous (64 h) cold stress induced marked changes within the kisspeptin neural system along the celiac ganglion-ovary axis. In vitro incubation with the β-adrenergic agonist isoproterenol increased ovarian kisspeptin mRNA and peptide levels, and this increase was inhibited by treatment with the β-antagonist propranolol. Sectioning the superior ovarian nerve altered the feedback information within the kisspeptin celiac ganglion-ovary axis. In vivo administration of a kisspeptin antagonist to the left ovarian bursa of 22- to 50-d-old unilaterally ovariectomized rats delayed the vaginal opening, decreased the percentage of estrous cyclicity, and decreased plasma, ovarian, and celiac ganglion kisspeptin concentrations but did not modify the LH plasma levels. These results indicate that the intraovarian kisspeptin system may be regulated by sympathetic nerve activity and that the peptide, either from a neural or ovarian origin, is required for proper coordinated ovarian function.

Hormonal programming across the lifespan

Hormones influence countless biological processes across an animal's lifespan. Many hormone-mediated events occur within developmental sensitive periods, during which hormones have the potential to cause permanent tissue-specific alterations in anatomy and physiology. There are numerous selective critical periods in development with different targets being affected during different periods. This review outlines the proceedings of the Hormonal Programming in Development session at the US-South American Workshop in Neuroendocrinology in August 2011. Here we discuss how gonadal steroid hormones impact various biological processes within the brain and gonads during early development and describe the changes that take place in the aging female ovary. At the cellular level, hormonal targets in the brain include neurons, glia, or vasculature. On a genomic/epigenomic level, transcription factor signaling and epigenetic changes alter the expression of critical hormone receptor genes across development and following ischemic brain insult. In addition, organizational hormone exposure alters epigenetic processes in specific brain nuclei and may be an important mediator of sexual differentiation of the neonatal brain. Brain targets of hormonal programming, such as the paraventricular nucleus of the hypothalamus, may be critical in influencing the development of peripheral targets, such as the ovary. Exposure to excess hormones can cause abnormalities in the ovary during development leading to polycystic ovarian syndrome (PCOS). Exposure to excess androgens during fetal development also has a profound effect on the development of the male reproductive system. In addition, increased activity of the sympathetic nerve and stress during early life have been linked to PCOS symptomology in adulthood. Finally, we describe how age-related decreases in fertility are linked to high levels of nerve growth factor (NGF), which enhances sympathetic nerve activity and alters ovarian function.

Thyrotropin-releasing hormone causes a tonic excitatory postsynaptic current and inhibits the phasic inspiratory inhibitory inputs in inspiratory-inhibited airway vagal preganglionic neurons

The airway vagal preganglionic neurons (AVPNs) in the external formation of the nucleus ambiguus (eNA), which include the inspiratory-activated AVPNs (IA-AVPNs) and inspiratory-inhibited AVPNs (II-AVPNs), predominate in the control of the trachea and bronchia. The AVPNs receive particularly dense inputs from terminals containing thyrotropin-releasing hormone (TRH). TRH microinjection into the nucleus ambiguus (NA) caused constriction of the tracheal smooth muscles. However, it is unknown whether TRH affects all subtypes of the AVPNs in the eNA, and as a result affects the control of all types of target tissues in the airway (smooth muscles, submucosal glands, and blood vessels). It is also unknown how TRH affects the AVPNs at neuronal and synaptic levels. In this study, the AVPNs in the eNA were retrogradely labeled from the extrathoracic trachea, the II-AVPNs were identified in rhythmically firing brainstem slices, and the effects of TRH were examined using patch-clamp. TRH (100 nmol L(-1)) enhanced both the rhythm and the intensity of the hypoglossal bursts, and caused a tonic excitatory inward current in the II-AVPNs at a holding voltage of -80 mV. The frequency of the spontaneous excitatory postsynaptic currents (EPSCs) in the II-AVPNs, which showed no respiratory-related change in a respiratory cycle, was not significantly changed by TRH. At a holding voltage of -50 mV, the II-AVPNs showed both spontaneous and phasic inspiratory (outward) inhibitory postsynaptic currents (IPSCs). TRH had no effect on the spontaneous IPSCs but significantly attenuated the phasic inspiratory outward currents, in both the amplitude and area. After focal application of strychnine, an antagonist of glycine receptors, to the II-AVPNs, the spontaneous IPSCs were extremely scarce and the phasic inspiratory inhibitory currents were abolished; and further application of TRH had no effect on these currents. Under current clamp configuration, TRH caused a depolarization and increased the firing rate of the II-AVPNs during inspiratory intervals. These results demonstrate that TRH affects the II-AVPNs both postsynaptically via a direct excitatory current and presynaptically via attenuation of the phasic glycinergic synaptic inputs.

Sympathetic nerve activity in normal and cystic follicles from isolated bovine ovary: local effect of beta-adrenergic stimulation on steroid secretion

Cystic ovarian disease (COD) is an important cause of abnormal estrous behavior and infertility in dairy cows. COD is mainly observed in high-yielding dairy cows during the first months post-partum, a period of high stress. We have previously reported that, in lower mammals, stress induces a cystic condition similar to the polycystic ovary syndrome in humans and that stress is a definitive component in the human pathology. To know if COD in cows is also associated with high sympathetic activity, we studied isolated small antral (5 mm), preovulatory (10 mm) and cystic follicles (25 mm). Cystic follicles which present an area 600 fold greater compared with preovulatory follicles has only 10 times less concentration of NE as compared with small antral and preovulatory follicles but they had 10 times more NE in follicular fluid, suggesting a high efflux of neurotransmitter from the cyst wall. This suggestion was reinforced by the high basal release of recently taken-up 3H-NE found in cystic follicles. While lower levels of beta-adrenergic receptor were found in cystic follicles, there was a heightened response to the beta-adrenergic agonist isoproterenol and to hCG, as measured by testosterone secretion. There was however an unexpected capacity of the ovary in vitro to produce cortisol and to secrete it in response to hCG but not to isoproterenol. These data suggest that, during COD, the bovine ovary is under high sympathetic nerve activity that in addition to an increased response to hCG in cortisol secretion could participate in COD development.

Cold-induced glutamate release in vivo from the magnocellular region of the paraventricular nucleus is involved in ovarian sympathetic activation

We previously reported that centrally-induced sympathetic activation in response to cold stress is associated with a polycystic ovarian condition in rats, and thyrotrophin-releasing hormone (TRH) released locally from the magnocellular region of the paraventricular nucleus (PVN) appears to be involved in this activation. Because TRH neurones express NMDA glutamate receptors, in the present study, we investigated the role of glutamate in the increased release of TRH from magnocellular neurones induced by cold stress and its relationship to ovarian neurotransmission. Animals with a push-pull cannula stereotaxically implanted into the magnocellular portion of the PVN were exposed to cold stress (4 degrees C for 64 h) and subjected to intracerebral perfusion. Perfusate fractions were obtained and analysed by high-performance liquid chromatography to measure glutamate and GABA levels. Glutamate, but not GABA, release increased significantly in animals perfused under cold exposure. In vivo administration of glutamate to the PVN increased TRH release. Injection of MK-801 into the magnocellular portion of the PVN reduced ovarian noradrenaline turnover and led to an increase in catecholamine concentration from the adrenal glands and celiac ganglia. Taken together, the results obtained in the present study strongly suggest that glutamate release from the magnocellular PVN is sensitive to cold stress and that glutamate acts through the NMDA receptor to mediate cold-induced TRH release. This in turn triggers hypothalamic-ovarian pathway activation, which might be responsible for the polycystic condition induced by cold stress and other ovarian pathologies characterised by increased sympathetic discharge.

Desipramine prevents stress-induced changes in depressive-like behavior and hippocampal markers of neuroprotection

Extracellular signal-regulated kinases (ERKs) are widely implicated in multiple physiological processes. Although ERK1/2 has been proposed as a common mediator of antidepressant action in naive rodents, it remains to be determined whether the ERK1/2 pathway plays a role in depressive disorder. Here, we investigated whether chronic restraint stress (14 days) and antidepressant treatment [desipramine (DMI), 10 mg/kg intraperitoneally] induce changes in animal behavior and hippocampal levels of phospho-ERK1/2 and its substrate phospho-cAMP response element-binding protein (CREB). The results indicated that stress-induced depressive-like behaviors were correlated with an increase in P-ERK1/2 and P-CREB in the hippocampus evaluated by immunoblot analysis. As an indication of CREB activity, we evaluated changes in mRNA levels of its target genes. Brain-derived neurotrophic factor (BDNF) mRNA was reduced by stress, an effect prevented by DMI only in the CA3 area of hippocampus. Bcl-2 mRNA was reduced in all hippocampal regions by stress, an effect independent of DMI treatment. However, immunoblot from hippocampal extracts revealed that stress increased BCL-2 levels, an effect prevented by chronic DMI. These results suggest that ERKs and BDNF may be altered in depressive disorder, modifications that are sensitive to DMI action. In contrast, the stress-induced increase in BCL-2 may correspond to a neuroprotective response.

Selective activation of the sympathetic ganglia by centrally administered corticotropin-releasing factor in rats

The sympathetic efferent pathway projects to the sympathetic ganglia and the adrenal medulla. In this study, we examined centrally administered corticotropin-releasing factor (CRF)-induced neuronal activation of noradrenergic postganglionic neurons in several kinds of the sympathetic ganglia (superior cervical, stellate and celiac ganglia) in anesthetized rats. CRF significantly increased c-Fos expression in the celiac and stellate ganglia, with more pronounced effect on the celiac ganglion. On the other hand, CRF had no effect on c-Fos expression in the superior cervical ganglion even at a higher dose. These results suggest that brain CRF selectively regulates neuronal activity of each sympathetic ganglion.

Chronic-intermittent cold stress in rats induces selective ovarian insulin resistance

In rat ovary chronic cold stress increases sympathetic nerve activity, modifies follicular development, and initiates a polycystic condition. To see whether there is a relationship between the previously described changes in follicular development and metabolic changes similar to those in women with polycystic ovary, we have studied the effect of chronic cold stress (4 degrees C for 3 h/day, Monday to Friday, for 4 wk) on insulin sensitivity and the effect of insulin on sympathetic ovarian activity. Although cold-stressed rats ate more than the controls, they did not gain more weight. Insulin sensitivity, determined by hyperinsulinemic-euglycemic clamp, was significantly increased in the stressed animals. Insulin in vitro increased the basal release of norepinephrine from the ovaries of control rats but not from those of stressed rats, suggesting a local neural resistance to insulin in stressed rats. The levels of mRNA and protein for IRS1 and SLC2A4 (also known as GLUT4), molecules involved in insulin signaling, decreased significantly in the ovaries but not in the muscle of stressed rats. This decrease was preferentially located in theca-interstitial cells compared with granulosa cells, indicating that theca cells (the only cells directly innervated by sympathetic nerves) are responsible for the ovarian insulin resistance found in stressed rats. These findings suggest that ovarian insulin resistance produced by chronic stress could be in part responsible for the development of the polycystic condition induced by stress.

Locus coeruleus mediates cold stress-induced polycystic ovary in rats

Previous reports about the rat ovary have shown that cold stress promotes ovarian morphological alterations related to a polycystic ovary (PCO) condition through activation of the ovarian sympathetic nerves. Because the noradrenergic nucleus locus coeruleus (LC) is activated by cold stress and synaptically connected to the preganglionic cell bodies of the ovarian sympathetic pathway, this study aimed to evaluate the LC's role in cold stress-induced PCO in rats. Ovarian morphology and endocrine and sympathetic functions were evaluated after 8 wk of chronic intermittent cold stress (4 C, 3 h/d) in rats with or without LC lesion. The effect of acute and chronic cold stress upon the LC neuron activity was confirmed by Fos protein expression in tyrosine hydroxylase-immunoreactive neurons. Cold stress induced the formation of follicular cysts, type III follicles, and follicles with hyperthecosis alongside increased plasma estradiol and testosterone levels, irregular estrous cyclicity, and reduced ovulation. Considering estradiol release in vitro, cold stress potentiated the ovarian response to human chorionic gonadotropin. Ovarian norepinephrine (NE) was not altered after 8 wk of stress. However, LC lesion reduced NE activity in the ovary of cold-stressed rats, but not in controls, and prevented all the cold stress effects evaluated. Cold stress increased the number of Fos/tyrosine hydroxylase-immunoreactive neurons in the LC, but this effect was more pronounced for acute stress as compared with chronic stress. These results show that cold stress promotes PCO in rats, which apparently depends on ovarian NE activity that, under this condition, is regulated by the noradrenergic nucleus LC.