Pituitary-adrenal Response Research Articles

The amygdaloid body of the family Delphinidae: a morphological study of its central nucleus through calbindin-D28k.

The amygdala is a noticeable bilateral structure in the medial temporal lobe and it is composed of at least 13 different nuclei and cortical areas, subdivided into the deep nuclei, the superficial nuclei, and the remaining nuclei which contain the central nucleus (CeA). CeA mediates the behavioral and physiological responses associated with fear and anxiety through pituitary-adrenal responses by modulating the liberation of the hypothalamic Corticotropin Releasing Factor/Hormone. Five dolphins of three different species, belonging to the family Delphinidae (three striped dolphins, one common dolphin, and one Atlantic spotted dolphin), were used for this study. For a precise overview of the CeA's structure, thionine staining and the immunoperoxidase method using calbindin D-28k were employed. CeA extended mainly dorsal to the lateral nucleus and ventral to the striatum. It was medial to the internal capsule and lateral to the optic tract and the medial nucleus of the amygdala. The dolphin amygdaloid complex resembles that of primates, including the subdivision, volume, and location of the CeA.

The Pituitary-Adrenal Response to Paradoxical Sleep Deprivation Is Similar to a Psychological Stressor, Whereas the Hypothalamic Response Is Unique.

Stressors of different natures induce activation of the hypothalamic-pituitary-adrenal (HPA) axis at different magnitudes. Moreover, the HPA axis response to repeated exposure is usually distinct from that elicited by a single session. Paradoxical sleep deprivation (PSD) augments ACTH and corticosterone (CORT) levels, but the nature of this stimulus is not yet defined. The purpose of the present study was to qualitatively compare the stress response of animals submitted to PSD to that of rats exposed once or four times to cold, as a physiological stress, movement restraint (RST) as a mixed stressor and predator odour (PRED) as the psychological stressor, whilst animals were submitted for 1 or 4 days to PSD and respective control groups. None of the stressors altered corticotropin releasing factor immunoreactivity in the paraventricular nucleus of the hypothalamus (PVN), median eminence (ME) or central amygdala, compared to control groups, whereas vasopressin immunoreactivity in PSD animals was decreased in the PVN and increased in the ME, indicating augmented activity of this system. ACTH levels were higher after repeated stress or prolonged PSD than after single- or 1 day-exposure and control groups, whereas the CORT response was habituated by repeated stress, but not by 4-days PSD. This dissociation resulted in changes in the CORT : ACTH ratio, with repeated cold and RST decreasing the ratio compared to single exposure, but no change was seen in PRED and PSD groups. Comparing the magnitude and pattern of pituitary-adrenal response to the different stressors, PSD-induced responses were closer to that shown by PRED-exposed rats. In contrast, the hypothalamic response of PSD-exposed rats was unique, inasmuch as this was the only stressor which increased the activity of the vasopressin system. In conclusion, we propose that the pituitary-adrenal response to PSD is similar to that induced by a psychological stressor.

Pituitary-Adrenal Responses and Glucocorticoid Receptor Expression in Critically Ill Patients with COVID-19.

The hypothalamus–pituitary–adrenal (HPA) axis was described as the principal component of the stress response 85 years ago, along with the acute-phase reaction, and the defense response at the tissue level. The orchestration of these processes is essential since systemic inflammation is a double-edged sword; whereas inflammation that is timely and of appropriate magnitude is beneficial, exuberant systemic inflammation incites tissue damage with potentially devastating consequences. Apart from its beneficial cardiovascular and metabolic effects, cortisol exerts a significant immunoregulatory role, a major attribute being that it restrains the excessive inflammatory reaction, thereby preventing unwanted tissue damage. In this review, we will discuss the role of the HPA axis in the normal stress response and in critical illness, especially in critically ill patients with coronavirus disease 2019 (COVID-19). Finally, a chapter will be dedicated to the findings from clinical studies in critical illness and COVID-19 on the expression of the mediator of glucocorticoid actions, the glucocorticoid receptor (GCR).

Offensive Behavior, Striatal Glutamate Metabolites, and Limbic-Hypothalamic-Pituitary-Adrenal Responses to Stress in Chronic Anxiety.

Variations in anxiety-related behavior are associated with individual allostatic set-points in chronically stressed rats. Actively offensive rats with the externalizing indicators of sniffling and climbing the stimulus and material tearing during 10 days of predator scent stress had reduced plasma corticosterone, increased striatal glutamate metabolites, and increased adrenal 11-dehydrocorticosterone content compared to passively defensive rats with the internalizing indicators of freezing and grooming, as well as to controls without any behavioral changes. These findings suggest that rats that display active offensive activity in response to stress develop anxiety associated with decreased allostatic set-points and increased resistance to stress.

Associations between physiological responses to social-evaluative stress and daily functioning in first-episode schizophrenia

Schizophrenia (SZ) is associated with impaired adaptive functioning, including difficulties managing the demands of independent living, work, school, and interpersonal relationships. Prior studies have linked the physiological stress response with less effective coping in daily life. Differences in stress-response tendencies may also support heterogeneity in daily functioning in SZ. The present study examined two established measures of the stress response in patients with first-episode SZ. Salivary cortisol was included as an index of hypothalamic–pituitary–adrenal response. Vagal suppression (VS), a measure of stress-related reduction in heart rate variability, was used to assess parasympathetic flexibility. Greater cortisol response and VS to social-evaluative stress were predicted to be associated with better functioning in SZ over and above relationships with social cognition and neurocognition, two well-established predictors of functional outcome. Thirty-eight first-episode SZ outpatients and 29 healthy comparison subjects (HC) provided social cognitive, neurocognitive, and physiological measurements before and after the Trier Social Stress Test (TSST). Although SZ and HC did not differ on VS to the TSST, patients exhibited significant associations between VS and functioning across all four domains of the Role Functioning Scale. Furthermore, greater VS predicted more effective functioning with friends, beyond the contributions associated with social cognition and neurocognition, and strengthened the positive effects of higher levels of social cognition on independent living/self-care. VS elicited by social-evaluative stress in the laboratory may reflect stress-response tendencies in daily life that are relevant for daily functioning in first-episode SZ.

Caloric restriction modulates the monoaminergic and glutamatergic systems in the hippocampus, and attenuates age-dependent spatial memory decline.

The beneficial effects of caloric restriction (CR) on health and life expectancy are well documented, although its ability to slow down age-dependent cognitive decline and the underlying biochemical changes remains unclear. Therefore, the aim of this study was to investigate the effects of CR on spatial memory in aged Wistar rats, as well as on monoaminergic and glutamatergic neurotransmission in the hippocampus (HPC). As such, animals maintained on different dietary regimes were trained in the Morris Water Maze (MWM): old rats (24-27 months) maintained on a 30% CR diet from four months of age, old rats (24-27 months) with unrestricted access to food (Ad Libitum); and adult rats (3-4 months) with Ad Libitum access to food. As well as their performance in the spatial memory task, monoamine levels, and NMDA and AMPA receptor subunit expression in the HPC were also assessed in these rats, as was the plasma corticosterone as a measure of the pituitary-adrenal response to stress. Accordingly, it appears that CR attenuates the spatial memory decline in aged rats and the age-associated decrease in the serotonin metabolite 5-HIAA, as well as the expression of the GluA1 and GluA2 AMPA receptor subunits in the HPC. In addition, CR augments the noradrenaline in this structure, although it did not modify the age-associated increase in plasma corticosterone levels. These findings support the positive effect of CR on spatial memory, suggesting that enhancing monoaminergic and glutamatergic neurotransmission in the HPC may help improve learning and memory in aged animals.

Reduction of acute mild stress corticosterone response and changes in stress-responsive gene expression in male Balb/c mice after repeated administration of a Rhodiola rosea L. root extract.

Rhodiola rosea L. (R. rosea) is an adaptogenic plant increasing body resistance to stress. Its efficacy has been evidenced mainly in chronic stress models, data concerning its effect in acute stress and underlying mechanisms being scarce. The objective was to investigate the effect of repeated doses of a R. rosea hydroethanolic root extract (HRE) on hypothalamic pituitary adrenal response in a murine model of acute mild stress and also the mechanisms involved. Stress response was measured in Balb/c mice having received by gavage HRE (5 g/kg) or vehicle daily for 2 weeks before being submitted to an acute mild stress protocol (open‐field test then elevated plus maze). Corticosterone was measured in plasma from mandibular vein blood drawn before and 30, 60, and 90 min after initiation of the stress protocol. Mice were sacrificed at 90 min, and the hippocampus, prefrontal cortex, and amygdala were excised for high‐frequency RT‐PCR gene expression analysis. At 30 min after acute mild stress induction, corticosterone level in mice having received the HRE was lower than in control mice and comparable to that in nonstressed mice in the HRE group. HRE administration induced brain structure‐dependent changes in expression of several stress‐responsive genes implicated in neuronal structure, HPA axis activation, and circadian rhythm. In the acute mild stress model used, R. rosea HRE decreased corticosterone level and increased expression of stress‐responsive genes, especially in the hippocampus and prefrontal cortex. These findings suggest that R. rosea HRE could be of value for modulating reactivity to acute mild stress.

Sex- and Stress-Dependent Effects on Dendritic Morphology and Spine Densities in Putative Orexin Neurons

We recently found that non-stressed female rats have higher basal prepro-orexin expression and activation of orexinergic neurons compared to non-stressed males, which lead to impaired habituation to repeated restraint stress at the behavioral, neural, and endocrine level. Here, we extended our study of sex differences in the orexin system by examining spine densities and dendritic morphology in putative orexin neurons in adult male and female rats that were exposed to 5 consecutive days of 30-min restraint. Analysis of spine distribution and density indicated that putative orexinergic neurons in control non-stressed females had significantly more dendritic spines than those in control males, and the majority of these were mushroom spines. This morphological finding may suggest more excitatory input onto orexin neurons in female rats. As orexin neurons are known to promote the hypothalamic–pituitary–adrenal response, this morphological change in orexin neurons could underlie the impaired habituation to repeated stress in female rats. Dendritic complexity did not differ between non-stressed males and females, however repeated restraint stress decreased total dendritic length, nodes, and branching primarily in males. Thus, reduced dendritic complexity of putative orexinergic neurons is observed in males but not in females after 5days of repeated restraint stress. This morphological change might be reflective of decreased orexin system function, which may allow males to habituate more fully to repeated restraint than females. These results extend our understanding of the role of orexin neurons in regulating habituation and demonstrate changes in putative orexin cell morphology and spines that may underlie sex differences in habituation.

Relationship between sympathoadrenal and pituitary-adrenal response during colorectal distention in the presence of corticotropin-releasing hormone in patients with irritable bowel syndrome and healthy controls.

Corticotropin-releasing hormone (CRH) mediates stress responses in the brain-gut axis. Administration of CRH modulates brain activation, for example by controlling the autonomic nervous system in response to colorectal distention. Here, we investigated the relationship between sympathoadrenal and hypothalamic-pituitary-adrenal (HPA) responses to colorectal distention in patients with irritable bowel syndrome (IBS). We enrolled 32 patients with IBS (16 women and 16 men) and 32 healthy subjects (16 women and 16 men), and randomly divided them between CRH and saline injection groups. The patients randomly underwent no (0 mmHg), mild (20 mmHg), or strong (40 mmHg) colorectal distension. CRH (2 μg/kg) or saline was then administered via injection, and the distention protocol was repeated. The heart rate (HR) and HR variability (HRV; calculated as the low [LF] to high frequency [HF] peak ratio, LF/HF) were analyzed using electrocardiography. Plasma noradrenaline, adrenaline, adrenocorticotropic hormone (ACTH), and cortisol levels were measured at the time of each distention. Plasma adrenaline levels were shown to be associated with plasma ACTH levels in HCs injected with CRH during distention using structural equation modeling analysis. Patients with IBS injected with placebo during distention displayed a closer association between these two parameters than those injected with CRH. Generalized estimating equation analysis revealed a significant distention × group × drug interaction for HF power. Moreover, there was a strong correlation between adrenaline and HRV upon CRH injection in controls, but not patients with IBS. The relationship between HPA-sympathoadrenal responses and CRH levels during colorectal distention differs between patients with IBS and controls. Modulation of adrenal gland activity in response to ACTH stimulation may contribute to the brain-gut pathophysiology characteristic of IBS.

The impact of peri-operative dexamethasone administration on the normal hypothalamic pituitary adrenal response to major surgical procedures.

Surgical procedures are associated with activation of the hypothalamic-pituitary-adrenal axis (HPA). Studies examining HPA dynamics peri-operatively are limited and the modulating influence of peri-operatively administered glucocorticoids on that is not well established. This investigation examined alterations in HPA function and the impact of dexamethasone (DEX) administration during the peri-operative period. We examined HPA function in 297 patients with normal function who had surgical procedures including pituitary mass resection (n = 191), craniotomy (n = 17) and other thoracic/ abdominal/ pelvic surgeries (n = 89). HPA function was assessed by frequent measurements of parameters defining adrenal function: ACTH, cortisol, DHEA and DHEA-S levels for 48 h. DEX was administered as a single dose (2-10 mg) to 30 and as multiple doses (12-36 mg) to 21 patients. The data of DEX-treated subjects within each group were similar and were combined together. Pre-operative data were similar for patients having different surgical procedures. Without DEX exposure, ACTH increased to 225 ± 100 ng/L at 2-4 h and gradually declined to baseline values by 36 h while cortisol levels peaked (39.2 ± 13.2 ug/dL) at 6-8 h declining gradually thereafter. Cortisol rise was paralleled by an equimolar increase in DHEA and a subsequent increase in DHEA-S levels. Single doses of DEX did not influence ACTH or cortisol secretion but suppressed the expected rise in DHEA and DHEA-S levels. Multiple doses of DEX suppressed ACTH and cortisol after the 15th postoperative hour and completely blocked the expected rise in DHEA and DHEA-S levels. The data provide a detailed overview of HPA function in a large number of subjects who had major surgical procedures. Single and large doses of DEX did not suppress ACTH or cortisol secretion but suppressed adrenal androgen secretion. It took multiple doses of DEX to partially suppress ACTH and cortisol secretion in the peri-operative period.

50 Years Ago in The Journal of Pediatrics: Pituitary-Adrenal Responsiveness after Corticosteroid Therapy in Children with Nephrosis

50 Years Ago in The Journal of Pediatrics: Pituitary-Adrenal Responsiveness after Corticosteroid Therapy in Children with Nephrosis

The Role of ACTH and Corticosteroids for Sepsis and Septic Shock: An Update.

Sepsis is a common disorder associated with high morbidity and mortality. It is now defined as an abnormal host response to infection, resulting in life-threatening dysfunction of organs. There is evidence from in vitro and in vivo experiments in various animal models and in patients that endotoxin or sepsis may directly and indirectly alter the hypothalamic–pituitary–adrenal response to severe infection. These alterations may include necrosis or hemorrhage or inflammatory mediator-mediated decreased ACTH synthesis, steroidogenesis, cortisol delivery to tissues, clearance from plasma, and decreased sensitivity of tissues to cortisol. Disruption of the hypothalamic–pituitary–adrenal axis may translate in patients with sepsis into cardiovascular and other organ dysfunction, and eventually an increase in the risk of death. Exogenous administration of corticosteroids at moderate dose, i.e., <400 mg of hydrocortisone or equivalent for >96 h, may help reversing sepsis-associated shock and organ dysfunction. Corticosteroids may also shorten the duration of stay in the ICU. Except for increased blood glucose and sodium levels, treatment with corticosteroids was rather well tolerated in the context of clinical trials. The benefit of treatment on survival remains controversial. Based on available randomized controlled trials, the likelihood of survival benefit is greater in septic shock versus sepsis patients, in sepsis with acute respiratory distress syndrome or with community-acquired pneumonia versus patients without these conditions, and in patients with a blunted cortisol response to 250 μg of ACTH test versus those with normal response.

PSD-95 regulates CRFR1 localization, trafficking and β-arrestin2 recruitment

Corticotropin-releasing factor (CRF) is a neuropeptide commonly associated with the hypothalamic–pituitary adrenal axis stress response. Upon release, CRF activates two G protein-coupled receptors (GPCRs): CRF receptor 1 (CRFR1) and CRF receptor 2 (CRFR2). Although both receptors contribute to mood regulation, CRFR1 antagonists have demonstrated anxiolytic and antidepressant-like properties that may be exploited in the generation of new pharmacological interventions for mental illnesses. Previous studies have demonstrated CRFR1 capable of heterologously sensitizing serotonin 2A receptor (5-HT2AR) signaling: another GPCR implicated in psychiatric disease. Interestingly, this phenomenon was dependent on Postsynaptic density 95 (PSD-95)/Disc Large/Zona Occludens (PDZ) interactions on the distal carboxyl termini of both receptors. In the current study, we demonstrate that endogenous PSD-95 can be co-immunoprecipitated with CRFR1 from cortical brain homogenate, and this interaction appears to be primarily via the PDZ-binding motif. Additionally, PSD-95 colocalizes with CRFR1 within the dendritic projections of cultured mouse neurons in a PDZ-binding motif-dependent manner. In HEK 293 cells, PSD-95 overexpression inhibited CRFR1 endocytosis, whereas PSD-95 shRNA knockdown enhanced CRFR1 endocytosis. Although PSD-95 does not appear to play a significant role in CRF-mediated cAMP or ERK1/2 signaling, PSD-95 was demonstrated to suppress β-arrestin2 recruitment: providing a potential mechanism for PSD-95's inhibition of endocytosis. In revisiting previously documented heterologous sensitization, PSD-95 shRNA knockdown did not prevent CRFR1-mediated enhancement of 5-HT2AR signaling. In conclusion, we have identified and characterized a novel functional relationship between CRFR1 and PSD-95 that may have implications in the design of new treatment strategies for mental illness.

Mo2048 Altered Relation of Autonomic Response and Pituitary-Adrenal Response During Colorectal Distention With Corticotropin-Releasing Hormone in Irritable Bowel Syndrome

Background Searching biomarkers of irritable bowel syndrome (IBS) is emerging topic. Previous studies searched limited biomarkers and largely ignored real exacerbation of IBS symptoms in patient's life. We hypothesized that we can identify biomarkers of IBS which are associated with changes in IBS symptoms using urinary metabolomics.Methods Subjects were 25 IBS patients (33.0 ± 2.1 y.o., 15 male, 10 female) diagnosed with Rome III criteria (12 with diarrhea, 11 mixed, and 2 with constipation) and ageand sexmatched healthy controls. Subjects completed ordinate scales containing abdominal pain and discomfort everyday for 28 days. Simultaneously urinary samples were collected at the first day, the day with exacerbation, and the 28th day with questionnaires including IBS Severity Index (IBS-SI) and IBS Quality of Life (IBS-QOL). Urinary samples were immediately frozen, stored, and later analyzed with ultraperformance liquid chromatography and mass spectrometry. After correction with creatinine, data were analyzed statistically with generalized estimating equation (GEE) using SPSS ver. 21.0 followed by multiple regression analysis with IBS symptoms as dependent variables and metabolites as independent variables. Results We first identified 191 metabolome markers. GEE revealed significant 44 markers with group (IBS vs controls) effect and/or time effect and/or group time interaction. IBS patients showed significantly lower kynurenic acid (p < 0.005), xanthurenic acid (p < 0.001), homovanillic acid (p < 0.005), vanillylmandelic acid (p < 0.005) and glycylglycine (p < 0.001) than controls. IBS patients showed significantly higher quinolinic acid (p < 0.01), 3-methoxytyamine (p < 0.05), xylose (p < 0.005), 2'-deoxyguanosine (p < 0.001), 2'-deoxyadenosine (p < 0.05), and N-acetylarginine (p < 0.05) than controls. Multiple regression analysis disclosed xylose as significant predictor of abdominal pain (R2 = 0.859, b = 0.59, p < 0.0001). Conclusion These findings support our hypothesis and suggest that increased urinary xylose level reflects increased mucosal permeability in IBS patients. Moreover, increased quinolinic acid and decreased kynurenic and xanthurenic acids in IBS patients may cause toxicity of the glutamatergic neurons expressing NMDA receptors both in the brain and the gut.

Sex differences in the behavioural and hypothalamic–pituitary–adrenal response to contextual fear conditioning in rats

In recent years, special attention is being paid to sex differences in susceptibility to disease. In this regard, there is evidence that male rats present higher levels of both cued and contextual fear conditioning than females. However, little is known about the concomitant hypothalamic–pituitary–adrenal (HPA) axis response to those situations which are critical in emotional memories. Here, we studied the behavioural and HPA responses of male and female Wistar rats to context fear conditioning using electric footshock as the aversive stimulus. Fear-conditioned rats showed a much greater ACTH and corticosterone response than those merely exposed to the fear conditioning chamber without receiving shocks. Moreover, males presented higher levels of freezing whereas HPA axis response was greater in females. Accordingly, during the fear extinction tests, female rats consistently showed less freezing and higher extinction rate, but greater HPA activation than males. Exposure to an open-field resulted in lower activity/exploration in fear-conditioned males, but not in females, suggesting greater conditioned cognitive generalization in males than females. It can be concluded that important sex differences in fear conditioning are observed in both freezing and HPA activation, but the two sets of variables are affected in the opposite direction: enhanced behavioural impact in males, but enhanced HPA responsiveness in females. Thus, the role of sex differences on fear-related stimuli may depend on the variables chosen to evaluate it, the greater responsiveness of the HPA axis in females perhaps being an important factor to be further explored.

Neonatal amygdala lesions lead to increased activity of brain CRF systems and hypothalamic-pituitary-adrenal axis of juvenile rhesus monkeys.

The current study examined the long-term effects of neonatal amygdala (Neo-A) lesions on brain corticotropin-releasing factor (CRF) systems and hypothalamic-pituitary-adrenal (HPA) axis function of male and female prepubertal rhesus monkeys. At 12-months-old, CSF levels of CRF were measured and HPA axis activity was characterized by examining diurnal cortisol rhythm and response to pharmacological challenges. Compared with controls, Neo-A animals showed higher cortisol secretion throughout the day, and Neo-A females also showed higher CRF levels. Hypersecretion of basal cortisol, in conjunction with blunted pituitary-adrenal responses to CRF challenge, suggest HPA axis hyperactivity caused by increased CRF hypothalamic drive leading to downregulation of pituitary CRF receptors in Neo-A animals. This interpretation is supported by the increased CRF CSF levels, suggesting that Neo-A damage resulted in central CRF systems overactivity. Neo-A animals also exhibited enhanced glucocorticoid negative feedback, as reflected by an exaggerated cortisol suppression following dexamethasone administration, indicating an additional effect on glucocorticoid receptor (GR) function. Together these data demonstrate that early amygdala damage alters the typical development of the primate HPA axis resulting in increased rather than decreased activity, presumably via alterations in central CRF and GR systems in neural structures that control its activity. Thus, in contrast to evidence that the amygdala stimulates both CRF and HPA axis systems in the adult, our data suggest an opposite, inhibitory role of the amygdala on the HPA axis during early development, which fits with emerging literature on "developmental switches" in amygdala function and connectivity with other brain areas.

Coping and glucocorticoid receptor regulation by stress inoculation.

Intermittent exposure to mildly stressful situations provides opportunities to practice coping in the context of exposure psychotherapies and stress inoculation training. Previously, we showed that stress inoculation modeled in juvenile monkeys enhances subsequent indications of resilience. Here we examine stress inoculation effects in adult female monkeys. We found that stress inoculation prevents social separation stress induced anhedonia measured using sucrose preference tests and reduces the hypothalamic pituitary adrenal (HPA) axis stress hormone response to a novel environment. Stress inoculation also increases glucocorticoid receptor (NR3C1) gene expression in anterior cingulate cortex but not hippocampus. Increased anterior cingulate cortex NR3C1 expression induced by stress inoculation is not associated with significant changes in GR1F promoter DNA methylation. On average, low levels of promoter DNA methylation and limited GR1F expression were evident in monkey anterior cingulate cortex as observed in corticolimbic brain regions of adult humans. Taken together these findings suggest that stress inoculation in adulthood enhances behavioral and hormonal aspects of coping without significantly influencing GR1F promoter DNA methylation as a mechanism for NR3C1 transcription regulation.

Expression of maternal behavior and activation of the bed nucleus of the stria terminalis during predatory threat exposure: Modulatory effects of transport stress

Past work has established that levels of maternal care provided to rat pups during the postpartum period plays an important role in shaping development of the stress response system, such that high levels of pup licking and grooming and active nursing behaviors are associated with more efficient hypothalamic–pituitary–adrenal responses to stressors in adulthood. Furthermore, a prior study from our laboratory has demonstrated facilitation of maternal care for five days following a one-hour predator odor exposure on the day of giving birth. The present study was an investigation of the effects on maternal care during a one-hour predator odor exposure administered on the day of giving birth, with or without the addition of transport stress immediately prior to the odor exposure. Stress-induced activation of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST), two brain regions involved in regulating maternal behaviors, were also quantified using c-Fos immunohistochemistry. Our results show that predator odor exposure soon after birth does not significantly alter expression of maternal behaviors during the hour-long exposure period, unless the dams are also exposed to transport stress, in which case maternal behaviors are reduced during the first 10min of the exposure but not significantly different during the final 10min. Predator odor exposure (with or without additional transport stress) increased c-Fos immunoreactivity in the BNST, but not the MPOA, relative to control odor exposure, suggesting that the BNST may play an important role in integration of threat cues and transduction of their meaning into long-term effects on expression of maternal care. Future experiments should be designed to test the effects of temporary inactivation of the BNST during postpartum predator odor exposure.

Effects of age on ACTH, corticosterone, glucose, insulin, and mRNA levels during intermittent hypoxia in the neonatal rat

Apnea, the temporary cessation of respiratory airflow, is a common cause of intermittent hypoxia (IH) in premature infants. We hypothesized that IH elicits a stress response and alters glucose homeostasis in the neonatal rat. Rat pups were studied on postnatal day (PD) 2, 8, 10, 12, and 14. Pups were exposed to normoxia (control) or six cycles consisting of 30-s exposures to hypoxia (FiO2 = 3%) over a 60-min period. Blood samples were obtained at baseline, after the third cycle (~30 min), and after the sixth cycle (~60 min). Tissue samples were collected following the sixth cycle. Plasma ACTH, corticosterone, glucose, and insulin were analyzed at all ages. Hypothalamic, pituitary, and adrenal mRNA expression was evaluated by quantitative PCR in PD2, PD8, and PD12 pups. Exposure to IH elicited significant increases in plasma ACTH and corticosterone at all ages studied. The largest increase in corticosterone occurred in PD2 pups, despite only a very small increase in plasma ACTH. This ACTH-independent increase in corticosterone in PD2 pups was associated with increases in adrenal Ldlr and Star mRNA expression. Additionally, IH caused hyperglycemia and hyperinsulinemia at all ages. We conclude that IH elicits a significant pituitary-adrenal response and significantly alters glucose homeostasis. Furthermore, the quantitative and qualitative characteristics of these responses depend on developmental age.

Early postnatal handling alters glucocorticoid receptor concentrations in selected brain regions.

Norway rat pups were either handled (H) or undisturbed (nonhandled, NH) in the period between birth and weaning on Day 21. Following weaning, half of the animals in each group were housed socially (Soc), and half were housed in isolation (Isol). At 120-150 days of age, all animals were sacrificed, and the following regions were dissected and frozen at -70 °C until the time of assay: frontal cortex, hippocampus, hypothalamus, amygdala, septum, and pituitary. [3H]Dexamethasone (3H Dex) binding in each region was examined by an in vitro, cytosol, receptor assay. 3H Dex binding was significantly higher in the hippocampus of both H-Soc and H-Isol than in NH groups. In the frontal cortex, 3H Dex binding was higher in the H-Soc animals than in the H-Isol and NH-Isol animals. There were no significant handling or housing effects found in the amygdala, hypothalamus, septum, or pituitary. Thus, early postnatal handling appears to influence the development of the glucocorticoid receptor system in the hippocampus and frontal cortex. These results are discussed as providing a possible mechanism for some of the previously reported effects of early handling on the development of the pituitary-adrenal response to stress.