Corticosterone Levels In Response Research Articles

Chemogenetic activation of CRF neurons as a model of chronic stress produces sex-specific physiological and behavioral effects

Trauma and chronic stress exposure are the strongest predictors of lifetime neuropsychiatric disease presentation. These disorders often have significant sex biases, with females having higher incidences of affective disorders such as major depression, anxiety, and PTSD. Understanding the mechanisms by which stress exposure heightens disease vulnerability is essential for developing novel interventions. Current rodent stress models consist of a battery of sensory, homeostatic, and psychological stressors that are ultimately integrated by corticotropin-releasing factor (CRF) neurons to trigger corticosteroid release. These stress paradigms, however, often differ between research groups in the type, timing, and duration of stressors utilized. These inconsistencies, along with the variability of individual animals’ perception and response to each stressor, present challenges for reproducibility and translational relevance. Here, we hypothesized that a more direct approach using chemogenetic activation of CRF neurons would recapitulate the effects of traditional stress paradigms and provide a high-throughput method for examining stress-relevant phenotypes. Using a transgenic approach to express the Gq-coupled Designer Receptor Exclusively Activated by Designer Drugs (DREADD) receptor hM3Dq in CRF-neurons, we found that the DREADD ligand clozapine-N-oxide (CNO) produced an acute and robust activation of the hypothalamic-pituitary-adrenal (HPA) axis, as predicted. Interestingly, chronic treatment with this method of direct CRF activation uncovered a novel sex-specific dissociation of glucocorticoid levels with stress-related outcomes. Despite hM3Dq-expressing females producing greater corticosterone levels in response to CNO than males, hM3Dq-expressing males showed significant typical physiological stress sensitivity with reductions in body and thymus weights. hM3Dq-expressing females while resistant to the physiological effects of chronic CRF activation, showed significant increases in baseline and fear-conditioned freezing behaviors. These data establish a novel mouse model for interrogating stress-relevant phenotypes and highlight sex-specific stress circuitry distinct for physiological and limbic control that may underlie disease risk.

THU118 Prefrontal-Medullary Circuit Is Necessary For Chronic Stress-Induced Neuroendocrine And Behavioral Outcomes

Abstract Disclosure: S.A. Pace: None. E. Lukinic: None. P. Barrette: None. T. Wallace: None. B. Myers: None. Chronic stress exposure is a major risk factor for psychiatric and cardiometabolic diseases. Although the pathologies associated with chronic stress are well-documented, the biological mechanisms underlying these physiological changes remain unknown. Human imaging studies indicate the prefrontal cortex is a key site for processing stress-related information. Within the rat prefrontal cortex, the infralimbic area (IL) is critical for regulating physiological stress reactivity in a sex-specific fashion. Here we examined the necessity of an IL downstream circuit for neurogenic regulation of neuroendocrine susceptibility after chronic stress. We focused on an IL to rostral ventrolateral medulla (RVLM) circuit due to the ability of the RVLM to initiate the sympatho-adrenomedullary stress responses and influence HPA axis activity. Critically, the IL-RVLM circuit is structurally positioned to underlie a crucial link between stress appraisal and sympathetic reactivity. To determine the role of the IL-RVLM circuit during chronic stress, an intersectional viral strategy was used to express a light-chain variant of Tetanus Toxin (TeLC) in RVLM-projecting IL neurons, thereby disrupting IL-RVLM signaling. TeLC-expressing IL neurons had less synaptobrevin-2 protein located on terminals and fewer synaptic appositions in the RVLM. This chronic circuit disruption approach was evaluated in the context of a 2-week chronic variable stress (CVS) paradigm in male and female rats. In males, CVS-exposed TeLC rats displayed decreased corticosterone levels in response to a novel stressor compared to control rats. CVS-naïve males showed no significant changes. In females, we similarly observed no differences in unstressed rats. However, CVS TeLC female rats had increased glycemic and corticosterone stress responses compared to CVS control animals. Additionally, female CVS TeLC rats had increased behavioral avoidance indicated by less time spent in the center of an open field arena compared to CVS control rats. This behavioral effect was not present in males. These results suggest that the IL-RVLM circuit is essential for preventing chronic stress outcomes in female rats, but not males. Further, this circuit regulation is necessary only after chronic stress exposure. Future studies will be aimed at determining sex differences in chronic stress effects on IL-RVLM signaling. Presentation: Thursday, June 15, 2023

A subpopulation of agouti-related peptide neurons exciting corticotropin-releasing hormone axon terminals in median eminence led to hypothalamic-pituitary-adrenal axis activation in response to food restriction.

The excitatory action of gamma-aminobutyric-acid (GABA) in the median-eminence (ME) led to the steady-state release of corticotropin-releasing hormone (CRH) from CRH axon terminals, which modulates the hypothalamic-pituitary-adrenal (HPA) axis. However, in ME, the source of excitatory GABAergic input is unknown. We examined agouti-related peptide (AgRP) expressing neurons in the arcuate nucleus as a possible source for excitatory GABAergic input. Here, we show that a subpopulation of activated AgRP neurons directly project to the CRH axon terminals in ME elevates serum corticosterone levels in 60% food-restricted mice. This increase in serum corticosterone is not dependent on activation of CRH neuronal soma in the paraventricular nucleus. Furthermore, conditional deletion of Na+-K+-2Cl– cotransporter-1 (NKCC1), which promotes depolarizing GABA action, from the CRH axon terminals results in significantly lower corticosterone levels in response to food restriction. These findings highlight the important role of a subset of AgRP neurons in HPA axis modulation via NKCC1-dependent GABAergic excitation in ME.

Maternal separation induced resilience to depression and spatial memory deficit despite intensifying hippocampal inflammatory responses to chronic social defeat stress in young adult male rats

Early life adversity has been suggested to affect neuroendocrine responses to subsequent stressors and accordingly vulnerability for behavioral disorders. This is the first work to study the effects of maternal separation (MS) stress on the co-occurrence of depression and cognitive impairments along with hippocampal inflammatory response under chronic social defeat stress (CSDS) in young adult male rats. During the first two postnatal weeks, the male pups were either exposed to MS or left undisturbed with their mothers (Std). Subsequently, starting on postnatal day 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent CSDS for three weeks. Totally, there were four groups (n = 10/group), namely Std-Con, Ms-Con, Std-CSDS, and MS-CSDS. Pup retrieval test was performed on daily basis from PND1 to PND14. During the last week of the CSDS exposure, in the light phase, the behavioral tests and the retro-orbital blood sampling were performed to assess basal plasma corticosterone levels. Afterwards, the hippocampus of the animals was removed to measure the interleukin 1β (IL-1β) content. Exposure to CSDS increased the plasma corticosterone levels and induced social avoidance along with memory deficit. Maternal separation intensified hippocampal IL-1β contents as well as the plasma corticosterone levels in response to CSDS. Meanwhile, it facilitated the spatial learning and potentiated resilience to social avoidance and memory deficit. In conclusion, although maternal separation increased the basal plasma corticosterone levels, it could facilitate the learning process and induce resilience to the onset of depression and memory deficit in response to CSDS, probably through the compensatory increase in maternal care and the induction of mild hippocampal inflammatory response.

Maternal separation in the light or dark phase of the circadian cycle has different effects on the corticosterone levels and anxiety-like behavior in male adult rats

Maternal care in early life is essential for the growth and development of an offspring. The light phase of the circadian cycle is the dam's most caring phase for her pups. Therefore, we hypothesized that, in the long term, maternal separation (an early-life stress model) in the light phase can be more deleterious than maternal separation in the dark phase. This study aims to compare the effects of maternal separation in the dark or light phase of the circadian cycle on the behavioral and physiological parameters of adult male Wistar rats. From the first to the fourteenth day of life, litters were separated from their mothers for six hours, forming the following experimental groups: Control (C), Maternal Separation in the Light (MSL), and Maternal Separation in the Dark (MSD). After weaning, these groups were left undisturbed until the start of behavioral tests in adulthood. Behavioral measures (standard diet intake, palatable diet intake, and anxiety-like behavior in the elevated plus maze), as well as retroperitoneal adipose tissue weight, and corticosterone levels in response to feeding stress, were assessed between the ages of 120 and 180 days. The results showed that, in adulthood, the food intake after an eight-hour fast or feeding stress had not changed. Anxiety behavior was analyzed by measuring time in the open or closed arms of the elevated plus-maze. The corticosterone levels were measured after food stress, and quantified by using the enzyme-linked immunosorbent assay (ELISA) method. The retroperitoneal adipose tissue weight was also measured. The MSD group presented higher corticosterone levels (MSD = 173.9 ± 12.7) when compared to the C (4.21 ± 0.3) and MSL (4.25 ± 0.28, p < 0.001) groups. In the anxiety test, we observed that the duration in the open arm was shorter for the MSL group (27.4 ± 3.7) compared to the control (112.9 ± 9.6, p < 00.1). There was no change in the MSD group compared to the control, with regard to the time spent in the open arm of the maze. An effect of maternal separation on the consumption of a palatable diet was observed. There was an increase in the palatable diet intake in the MSL (16.3 ± 1.9) and MSD (15.7 ± 0.5) groups compared to the control (11.4 ± 1.2, p < 0.05). In response to stress and food deprivation, there was no difference between groups in food consumption. The adipose tissue weight was higher in the MSD group (7.12 ± 0.29) compared to the control (4.21 ± 0.3) and MSL (4.25 ± 0.28, p < 0.001) groups. Based on the results observed, we concluded that the light-phase stress is more detrimental to emotional behavior during the first two weeks of life, and the dark-phase stress is more detrimental to Hypothalamus-Pituitary-Adrenal (HPA)-axis functioning. Furthermore, the higher intake of a palatable diet could be interpreted as a coping behavior to these early stress-related modifications.

Неонатальная воспалительная боль, когнитивная и стресс-реактивная функции у взрослых самцов и самок крыс

Repetitive neonatal pain may cause central nervous system disorders. Existing clinical data on the effect of neonatal pain on learning, memory and stress-reactivity of the hypothalamic-pituitary-adrenal axis (the HPA axis) are limited to adolescence and have mostly been obtained for male individuals. The mechanism of neonatal pain effect has not yet been researched. Ontogenetic studies carried out on different-sex specimen are crucial for prediction, prevention and treatment of adaptive behavioural disorders caused by neonatal pain stress. Lately, this has become even more relevant due to COVID-19 affecting new-borns in need of intensive therapy. In this study, the impact of neonatal inflammatory pain on adult cognition and hormonal stress response was investigated in male and female rats. Continuous neonatal pain was induced by hindpaw formalin injections on days one and two from birth. In adult rats, we assessed spatial learning and memory using the Morris water maze and evaluated HPA reactivity in response to the formalin test. No significant cognitive function differences were found between the experimental group of rats subjected to neonatal pain and the control group. Within the experimental group subjected to neonatal pain, males showed better long-term spatial memory than females. After testing the long-term memory, we evaluated HPA reactivity by corticosterone levels in response to a formalin test. This parameter was higher in males. Only females with neonatal pain showed differences between short-term and long-term memory, with poorer long-term memory. Possible causes of sex differences in the cognitive function and hormonal stress response in adult rats exposed to neonatal inflammatory pain are discussed.

Sex-Dependent Actions of Prenatal Stress on the Activity of the Hypothalamo-Hypophyseal-Adrenocortical System in Rats: The Role of Corticosteroid Receptors in the Brain

Prenatal stress is regarded as a risk factor for the development of diseases such as mental, cardiovascular, and metabolic disorders in later life. Dysregulation of the activity of the hypothalamo-hypophyseal-adrenocortical system (HHAS) is one of the mechanisms producing these disorders. Regulation of the HHAS is mediated by two types of receptor – mineralocorticoid (MR) and glucocorticoid receptors (GR) – in the corticolimbic structures of the brain. The link between prenatal stress, sex, and HHAS activity, as well as the role of central MR and GR in this interaction, has received insufficient study. We have investigated the effects of prenatal stress on HHAS activity in adult male and female rats and the expression of GR and MR in the hippocampus and medial prefrontal cortex (mPFC). Prenatal stress was modeled by subjecting pregnant female Wistar rats to 1-h restraint from days 15 to 19 of pregnancy. Basal HHAS activity and stress corticosterone levels in response to 30-min restraint were studied in their adult offspring. GR and MR expression was assessed by western blotting and also, in the hippocampus, by an immunohistochemical method. Prenatally stressed males displayed prolonged stress responses, while females showed increases in basal and stress reactivity, along with increases in the sensitivity of the HHAS to feedback signals. In males, changes in HHAS activity were accompanied by decreases in GR and MR content in the hippocampus and mPFC with an unaltered GR:MR ratio. Prenatally stressed females showed increased expression of GR protein and decreased quantities of MR protein in the hippocampus and an increased GR:MR ratio in both areas of the brain. The hippocampus of male and female animals showed changes in GR and MR content in field CA3 and the dentate gyrus. These data indicate that sex-dependent changes in GR and MR protein expression in the hippocampus and mPFC contribute to modifications of HHAS activity due to prenatal stress.

Perinatal high fat diet induces early activation of endocrine stress responsivity and anxiety-like behavior in neonates

The maternal environment has a profound effect on the development of offspring, including responses to stress mediated by the hypothalamic-pituitary-adrenal (HPA) axis. In rodents, perinatal high fat diet (HFD) has been shown to program the HPA axis in a manner that persists throughout adulthood, however the effects of perinatal HFD on stress-related behaviors and physiology in neonates are limited. The first two weeks of life in rodents are known as the stress hyporesponsive period, during which animals do not respond to stressors that are otherwise known to elicit behavioral and physiological responses in mature animals. As neonates emerge from the hyporesponsive period, the maturing neural systems mediating the HPA axis leads to the suppression of ultrasonic vocalizations (USVs) and movement in the presence of threatening stimuli, such as male adult rat odor. In this study, we investigated the effects of perinatal HFD exposure, spanning the maternal pregestation, gestation and lactation period, on stress-related behaviors and physiology in neonatal rat offspring throughout the stress hyporesponsive period. During the stress hyporesponsive period, postnatal day (PND) 7, HFD pups had higher corticosterone levels in response to the presence of male odor, produced fewer USVs, and had an increase in basal corticotropin releasing hormone (Crh) transcript levels in the paraventricular nucleus of the hypothalamus. As pup emerged from the stress hyporesponsive period, PND 13, HFD offspring exhibited higher adrenocorticotropic hormone (ACTH) levels in response to male odor, increased anxiety-like behaviors as shown by increased USVs and immobility, and lower glucocorticoid receptor (Nr3c1) transcript abundance in the ventral hippocampus. These results indicate an alteration in the typical physiological and behavioral responses to stress during the hyporesponsive period of the HPA axis as a function of perinatal HFD exposure, which involves changes in the regulation of key genes mediating the HPA axis.

Administration of the Antioxidant N-Acetyl-Cysteine in Pregnant Mice Has Long-Term Positive Effects on Metabolic and Behavioral Endpoints of Male and Female Offspring Prenatally Exposed to a High-Fat Diet.

A growing body of evidence suggests the consumption of high-fat diet (HFD) during pregnancy to model maternal obesity and the associated increase in oxidative stress (OS), might act as powerful prenatal stressors, leading to adult stress-related metabolic or behavioral disorders. We hypothesized that administration of antioxidants throughout gestation might counteract the negative effects of prenatal exposure to metabolic challenges (maternal HFD feeding during pregnancy) on the developing fetus. In this study, female C57BL/6J mice were fed HFD for 13 weeks (from 5-weeks of age until delivery) and were exposed to the N-acetyl-cysteine (NAC) antioxidant from 10-weeks of age until right before delivery. Body weight of the offspring was assessed following birth, up to weaning and at adulthood. The metabolic, neuroendocrine and emotional profile of the adult offspring was tested at 3-months of age. Prenatal HFD increased mother’s body weight and offspring’s weight at the time of weaning, when administered in conjunction with NAC. In females, NAC administration reduced high levels of leptin resulting from prenatal HFD. Prenatal NAC administration also resulted in greater glucose tolerance and insulin sensitivity while increasing adiponectin levels, as well as increasing exploratory behavior, an effect accompanied by reduced plasma corticosterone levels in response to restraint stress. Analysis of glutathione levels in the hypothalamus and in brown adipose tissue indicates that, while HFD administration to pregnant dams led to reduced levels of glutathione in the offspring, as in the male hypothalamus, NAC was able to revert this effect and to increase glutathione levels both in the periphery (Brown Adipose Tissue, both males and females) and in the central nervous system (males). Overall, results from this study indicate that the body redox milieu should be tightly regulated during fetal life and that buffering OS during pregnancy can have important long-term consequences on metabolic and behavioral endpoints.

Nicotinamide phosphoribosyltransferase and the hypothalamic-pituitary-adrenal axis of the rat.

Nicotinamide phosphoribosyltransferase (Nampt), also termed visfatin, catalyses the rate‑limiting step in the nicotinamide adenine dinucleotide (NAD) salvage pathway. In addition to its intracellular function (iNampt), extracellular Nampt (eNampt) also affects numerous intracellular signalling pathways. The current study investigated the role of Nampt in the regulation of the hypothalamic‑pituitary‑adrenal (HPA) axis in rats. At 1h after intraperitoneal administration of eNampt (4µg/100g) in adult male rats, serum adrenocorticotropic hormone(ACTH) and aldosterone levels remained unchanged, while corticosterone levels were notably elevated compared with the control group, as determined by ELISA. The results of reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) demonstrated that, in the hypothalami of eNampt‑treated rats, the mRNA expression levels of Fos proto‑oncogene, which is also termed c‑Fos, were not significantly different compared with the control group; however, the mRNA expression levels of proopiomelanocortin (POMC) were markedly increased in the pituitary gland of eNampt‑treated rats compared with the control group. Furthermore, in hypothalamic explants, ELISA results demonstrated that the addition of the eNampt protein exhibited no effect on corticotropin‑releasing hormone (CRH) release into the incubation medium and prevented potassium ion‑induced CRH release. Additionally, the eNampt‑induced increase in ACTH output by pituitary gland explants was not statistically significant, compared with the control group. However, RT‑qPCR indicated that exposure of pituitary gland explants to eNampt and CRH increased the levels of POMC mRNA expression; the effect of eNampt, but not CRH, was inhibited by FK866, which is a specific Nampt inhibitor. In primary rat adrenocortical cell cultures, eNampt exhibited no effect on basal aldosterone or corticosterone secretion, while increases in aldosterone and corticosterone levels in response to ACTH were retained. To assess the potential role of iNampt in the regulation of adrenal steroidogenesis, experiments involving a specific Nampt inhibitor, FK866, were performed. Exposure of cultured cells to FK866 notably lowered basal aldosterone and corticosterone output compared with the control group, and completely eliminated the response of cultured cells to ACTH. The results of the present study indicated that the injected eNampt may have increased the corticosterone serum levels by acting at the pituitary level. In addition, iNampt may exert a tonic stimulating effect on the secretion of aldosterone and corticosterone from rat adrenocortical cells, as normal iNampt levels were required to retain the response of cultured rat adrenocortical cells to ACTH. Thus, these data suggest an important physiological role of both iNampt and eNampt in the regulation of the HPA axis activity in the rat.

Chronic FAAH inhibition during nicotine abstinence alters habenular CB1 receptor activity and precipitates depressive-like behaviors

The role of the endocannabinoid system in nicotine addiction is being increasingly acknowledged. Acute inhibition of anandamide (AEA) degradation efficiently reduces nicotine withdrawal-induced affective symptoms in rats and fatty acid amide hydrolase (FAAH), the degradation enzyme of AEA, has been proposed as a possible treatment against nicotine addiction. However, it is unclear whether chronic inhibition of AEA during nicotine abstinence will have beneficial or deleterious affective side-effects. Using a rat model of nicotine addiction, we found that, during abstinence, rats injected daily with a FAAH inhibitor (URB597) developed a depressive-like phenotype. Our results show that in the nicotine abstinent rats, URB597 induced low saccharin consumption, persistent immobility in the forced swim test and increased corticosterone levels in response to stress. In addition, URB597decreased CB1 receptor binding and activity in the habenula, a key structure in the control of nicotine-related emotional states. In contrast, non-treated abstinent rats showed increased CB1 receptor activity and behaviors comparable to controls. No FAAH inhibition-induced alterations were observed in animals that had a previous history of saline self-administration. Taken together, our results suggest that chronic FAAH inhibition prevents the homeostatic adaptations of habenular CB1 receptor function that are necessary for the recovery from nicotine dependence.

Pre- and Postnatal Effects of Corticosterone on Fitness-Related Traits and the Timing of Endogenous Corticosterone Production in a Songbird.

Maternally derived corticosterone in the egg and corticosterone produced endogenously by altricial nestling birds play essential roles during development. Although persistently high corticosterone levels can be harmful, moderately elevated levels above baseline can lead to reallocation of resources between growth and maintenance to ensure immediate survival or to enhance the development of fitness-related traits. We tested two hypotheses concerning the fitness consequences of elevated corticosterone during prenatal and postnatal development in altricial house wrens: (1) elevated corticosterone shifts resources away from growth and immune function and (2) elevated corticosterone serves as a signal to allocate resources to fitness-related traits. We also explored the development of the stress response, hypothesizing that early-stage nestlings have little endogenously produced corticosterone, but that their baseline and stress-induced corticosterone levels increase with age. Nestlings hatching from corticosterone-injected eggs were lighter at hatching, but through compensatory growth, ended up heavier than controls near the time of fledging, an important, fitness-related trait. Nestlings that hatched from corticosterone-injected eggs and those given oral doses of corticosterone did not differ from controls in three other fitness-related traits: immunoresponsiveness, size, or haematocrit. Early- and late-stage nestlings had similar baseline corticosterone levels, and all nestlings increased their plasma corticosterone levels in response to a capture-and-restraint protocol, with older nestlings mounting a stronger stress-induced response than younger nestlings. These results suggest that prenatal exposure to corticosterone is important in shaping offspring phenotype and are consistent with the hypothesis that maternally derived corticosterone in the egg can have long-term, fitness-related effects on offspring phenotype.

Amphetamine withdrawal differentially affects hippocampal and peripheral corticosterone levels in response to stress

Amphetamine withdrawal is associated with heightened anxiety-like behavior, which is directly driven by blunted stress-induced glucocorticoid receptor-dependent serotonin release in the ventral hippocampus. This suggests that glucocorticoid availability in the ventral hippocampus during stress may be reduced during amphetamine withdrawal. Therefore, we tested whether amphetamine withdrawal alters either peripheral or hippocampal corticosterone stress responses. Adult male rats received amphetamine (2.5mg/kg, ip) or saline for 14 days followed by 2 weeks of withdrawal. Contrary to our prediction, microdialysis samples from freely-moving rats revealed that restraint stress-induced corticosterone levels in the ventral hippocampus are enhanced by amphetamine withdrawal relative to controls. In separate groups of rats, plasma corticosterone levels increased immediately after 20min of restraint and decreased to below stress-naïve levels after 1h, indicating negative feedback regulation of corticosterone following stress. However, plasma corticosterone responses were similar in amphetamine-withdrawn and control rats. Neither amphetamine nor stress exposure significantly altered protein expression or enzyme activity of the steroidogenic enzymes 11β-hydroxysteroid dehydrogenase (11β-HSD1) or hexose-6-phosphate dehydrogenase (H6PD) in the ventral hippocampus. Our findings demonstrate for the first time that amphetamine withdrawal potentiates stress-induced corticosterone in the ventral hippocampus, which may contribute to increased behavioral stress sensitivity previously observed during amphetamine withdrawal. However, this is not mediated by either changes in plasma corticosterone or hippocampal steroidogenic enzymes. Establishing enhanced ventral hippocampal corticosterone as a direct cause of greater stress sensitivity may identify the glucocorticoid system as a novel target for treating behavioral symptoms of amphetamine withdrawal.

Paternal retrievals increase testosterone levels in both male and female California mouse (Peromyscus californicus) offspring

The importance of maternal care on offspring development has received considerable attention, although more recently, researchers have begun to focus on the significance of paternal contributions. In the monogamous and bi-parental California mouse, fathers provide high levels of care, and therefore serve as a model system for studying paternal effects on behavior and underlying neuroendocrine mechanisms. Paternal retrievals in this species influence long term changes in brain (expression of arginine vasopressin—AVP) and behavior (aggression and parenting) in adult male offspring. Further, paternal retrievals induce a transient increase in testosterone (T) in male offspring, which is thought to mediate the relationship between paternal retrievals and AVP expression. Although the father–son relationship has been well characterized, few studies have examined father–daughter interactions. In California mice, paternal retrievals increase aggression in female offspring. Although T has been implicated in the regulation of female aggression, it remains unclear whether T may underlie long-term changes in female offspring aggression in response to paternal retrievals. In the current study, we examined the influence of paternal retrievals on T in both male and female offspring. Retrievals were manipulated experimentally by displacement of the pup and trunk blood was collected from retrieved, non-retrieved, and non-manipulated (baseline) pups. We found that fathers expressed similar levels of retrievals towards sons and daughters, and that T levels were elevated in retrieved, as compared to non-retrieved offspring. Similar to what has been previously described in male offspring and replicated here, female offspring that were retrieved had higher T levels than non-retrieved females. Neither females nor males experienced a change in corticosterone levels in response to retrievals suggesting offspring do not mount a stress response to paternal care. Therefore, our data suggest that paternal retrievals may serve similar functions in shaping adult behavior in both male and female offspring via modulation of hormone levels.

Do acupuncture needle size and needling depth matter? A laser Doppler imaging study

Purpose: Acupuncture has been used to relieve stress. Although recent studies have shown that acupuncture can reduce stress, its mechanism remains unclear. The present study investigated the effect of acupuncture on immobilization stressinduced neuroinflammation in the rat hypothalamus. Methods: Rats were immobilized for 60min. Manual acupuncturewas performed atHT7 during the immobilization period. Gene expression of several pro-inflammatory factors and serum level of stress hormone and PGE2 were evaluated using real-time PCR and ELISA, respectively. Results: The stress-alleviating effect of acupuncture was confirmed by inhibiting hypothalamic CRFmRNA expressions as well as serum corticosterone levels in response to immobilization stress. The mRNA expression of pro-inflammatory mediators including TNFand IL-1 in the hypothalamus increased significantly after immobilization stress. Acupuncture treatment at HT7 during the immobilization significantly suppressed the immobilization stress-induced increase of pro-inflammatory mediators in the hypothalamus. Also, acupuncture inhibited significant increases in hypothalamic COX-2 mRNA as well as serum PGE2 levels in response to immobilization stress. Conclusion: These data clearly suggest a stress-relieving effect of acupuncture and the inhibition of neuroinflammation as a possible action mechanism for its anti-stress effect. Contact: Mijung Yeom, myeom@khu.ac.kr

Effect of acupuncture stimulation on scopolamine-induced impairment of spatial working memory via activation of cholinergic system and regulation of BDNF and CREB expressions in rats

Purpose: Acupuncture has been used to relieve stress. Although recent studies have shown that acupuncture can reduce stress, its mechanism remains unclear. The present study investigated the effect of acupuncture on immobilization stressinduced neuroinflammation in the rat hypothalamus. Methods: Rats were immobilized for 60min. Manual acupuncturewas performed atHT7 during the immobilization period. Gene expression of several pro-inflammatory factors and serum level of stress hormone and PGE2 were evaluated using real-time PCR and ELISA, respectively. Results: The stress-alleviating effect of acupuncture was confirmed by inhibiting hypothalamic CRFmRNA expressions as well as serum corticosterone levels in response to immobilization stress. The mRNA expression of pro-inflammatory mediators including TNFand IL-1 in the hypothalamus increased significantly after immobilization stress. Acupuncture treatment at HT7 during the immobilization significantly suppressed the immobilization stress-induced increase of pro-inflammatory mediators in the hypothalamus. Also, acupuncture inhibited significant increases in hypothalamic COX-2 mRNA as well as serum PGE2 levels in response to immobilization stress. Conclusion: These data clearly suggest a stress-relieving effect of acupuncture and the inhibition of neuroinflammation as a possible action mechanism for its anti-stress effect. Contact: Mijung Yeom, myeom@khu.ac.kr

β-Endorphin neuronal transplantation into the hypothalamus alters anxiety-like behaviors in prenatal alcohol-exposed rats and alcohol-non-preferring and alcohol-preferring rats.

Alcohol exposure has adverse effects on stress physiology and behavioral reactivity. This is suggested to be due, in part, to the effect of alcohol on β-endorphin (β-EP)-producing neurons in the hypothalamus. In response to stress, β-EP normally provides negative feedback to the hypothalamic-pituitary-adrenal axis and interacts with other neurotransmitter systems in the amygdala to regulate behavior. We examined whether β-EP neuronal function in the hypothalamus reduces the corticosterone response to acute stress, attenuates anxiety-like behaviors, and modulates alcohol drinking in rats. To determine whether β-EP neuronal transplants modulate the stress response, anxiety behavior, and alcohol drinking, we implanted differentiated β-EP neurons into the paraventricular nucleus (PVN) of the hypothalamus of normal, prenatal alcohol-exposed, and alcohol-preferring (P) and alcohol-non-preferring (NP) rats. We then assessed corticosterone levels in response to acute restraint stress and other markers of stress response in the brain and anxiety-like behaviors in the elevated plus maze and open-field assays. We showed that β-EP neuronal transplants into the PVN reduced the peripheral corticosterone response to acute stress and attenuated anxiety-like behaviors. Similar transplants completely reduced the hypercorticosterone response and elevated anxiety behaviors in prenatal alcohol-exposed adult rats. Moreover, we showed that β-EP reduced anxiety behavior in P rats with minimal effects on alcohol drinking during and following restraint stress. These data further establish a role of β-EP neurons in the hypothalamus for regulating physiological stress response and anxiety behavior and resemble a potential novel therapy for treating stress-related psychiatric disorders in prenatal alcohol-exposed children and those genetically predisposed to increased alcohol consumption.

Bisphenol-A exposure during adolescence leads to enduring alterations in cognition and dendritic spine density in adult male and female rats

We have previously demonstrated that adolescent exposure of rats to bisphenol-A (BPA), an environmental endocrine disrupter, increases anxiety, impairs spatial memory, and decreases dendritic spine density in the CA1 region of the hippocampus (CA1) and medial prefrontal cortex (mPFC) when measured in adolescents in both sexes. The present study examined whether the behavioral and morphological alterations following BPA exposure during adolescent development are maintained into adulthood. Male and female, adolescent rats received BPA, 40μg/kg/bodyweight, or control treatments for one week. In adulthood, subjects were tested for anxiety and locomotor activity, spatial memory, non-spatial visual memory, and sucrose preference. Additionally, stress-induced serum corticosterone levels and dendritic spine density in the mPFC and CA1 were measured. BPA-treated males, but not females, had decreased arm visits on the elevated plus maze, but there was no effect on anxiety. Non-spatial memory, object recognition, was also decreased in BPA treated males, but not in females. BPA exposure did not alter spatial memory, object placement, but decreased exploration during the tasks in both sexes. No significant group differences in sucrose preference or serum corticosterone levels in response to a stress challenge were found. However, BPA exposure, regardless of sex, significantly decreased spine density of both apical and basal dendrites on pyramidal cells in CA1 but had no effect in the mPFC. Current data are discussed in relation to BPA dependent changes, which were present during adolescence and did, or did not, endure into adulthood. Overall, adolescent BPA exposure, below the current reference safe daily limit set by the U.S.E.P.A., leads to alterations in some behaviors and neuronal morphology that endure into adulthood.

A secretagogin locus of the mammalian hypothalamus controls stress hormone release.

A hierarchical hormonal cascade along the hypothalamic-pituitary-adrenal axis orchestrates bodily responses to stress. Although corticotropin-releasing hormone (CRH), produced by parvocellular neurons of the hypothalamic paraventricular nucleus (PVN) and released into the portal circulation at the median eminence, is known to prime downstream hormone release, the molecular mechanism regulating phasic CRH release remains poorly understood. Here, we find a cohort of parvocellular cells interspersed with magnocellular PVN neurons expressing secretagogin. Single-cell transcriptome analysis combined with protein interactome profiling identifies secretagogin neurons as a distinct CRH-releasing neuron population reliant on secretagogin's Ca(2+) sensor properties and protein interactions with the vesicular traffic and exocytosis release machineries to liberate this key hypothalamic releasing hormone. Pharmacological tools combined with RNA interference demonstrate that secretagogin's loss of function occludes adrenocorticotropic hormone release from the pituitary and lowers peripheral corticosterone levels in response to acute stress. Cumulatively, these data define a novel secretagogin neuronal locus and molecular axis underpinning stress responsiveness.

Adolescent bisphenol-A exposure decreases dendritic spine density: role of sex and age.

Bisphenol-A (BPA), a common environmental endocrine disruptor, modulates estrogenic, androgenic, and antiandrogenic effects throughout the lifespan. We recently showed that low dose BPA exposure during adolescence increases anxiety and impairs spatial memory independent of sex. In this study, six week old Sprague Dawley rats (n=24 males, n=24 females) received daily subcutaneous injections (40 µg/kg bodyweight) of BPA or vehicle for one week. Serum corticosterone levels in response to a 1 h restraint stress and spine density were examined at age 7 (cohort 1) and 11 (cohort 2) weeks. Adolescent BPA exposure did not alter stress dependent corticosterone responses but decreased spine density on apical and basal dendrites of pyramidal cells in the medial prefrontal cortex (mPFC) and hippocampal CA1 region (CA1). Sex differences in spine density were observed on basal dendrites of the mPFC and CA1 with females having greater spine density than males. This sex difference was further augmented by both age and treatment, with results indicating that BPA-dependent decreases in spine density were more pronounced in males than females on mPFC basal dendrites. Importantly, the robust neuronal alterations were observed in animals exposed to BPA levels below the current U.S.E.P.A. recommended safe daily limit. These results are the first demonstrating that BPA given during adolescence leads to enduring effects on neural morphology at adulthood. Given that humans are routinely exposed to low levels of BPA through a variety of sources, the decreased spine density reported in both male and female rats after BPA exposure warrants further investigation.