Age-appropriate acute stress, such as cold exposure, provokes the secretion of corticotropin releasing factor (CRF) from the hypothalamus, leading to a robust increase of plasma corticosterone in the immature rat. This activation of the hypothalamic-pituitary-adrenal system is accompanied by a stress-induced increase of steady-state CRF-mRNA expression in the hypothalamic paraventricular nucleus (PVN). In the current study, we analysed changes in CRF-mRNA expression in the PVN and the central nucleus of the amygdala (ACe) in the immature rat in response to a single episode of cold stress and three repeated exposures to this same stressor. CRF-mRNA expression in the PVN increased after a single, but not repeated exposures to cold stress, while repeated acute stress increased the content of the CRF peptide in the anterior hypothalamus. In the ACe, repeated episodes of cold stress resulted in increased expression of CRF-mRNA. These findings indicate a differential regulation of CRF gene expression in the PVN and ACe of the immature rat by single and repeated acute stress.

OBJECTIVE

To develop a clinical perspective on bilateral massive adrenal hemorrhage and an algorithm for its diagnosis and treatment.

METHODS

Case reports were identified through a computer search using MEDLIN (1976 to 1987), and from bibliographies in review articles (up to 1978).

METHODS

Twelve reports published since 1978 were found.

METHODS

Data from 20 recently reported cases and 5 cases from personal records were compared with data from 142 previously reported, autopsy-proven cases summarized in a 1978 review article.

RESULTS

Thromboembolic disease, coagulopathy, and the postoperative state were the three major risk factors. Except for abdominal pain and remittent fever, clinical features were not helpful in diagnosis. A fall in hemoglobin, and progressive biochemical hypoadrenalism were important clues. Diagnosis was confirmed by computed tomography and an absent cortisol response to intravenous corticotropin. Long-term follow-up showed complete atrophy and functional failure of the adrenal gland.

CONCLUSIONS

Death from bilateral massive adrenal hemorrhage can be prevented by pre-emptive steroid therapy in high-risk patients who have certain clinical and laboratory features.

BACKGROUND

There is an extensive literature describing a central serotonin deficit in alcoholic, impulsive, violent offenders and fire setters. In the present study, we investigated biochemical concomitants of impulsivity and aggressiveness, and the physiological consequences of reduced central serotonin turnover.

METHODS

Forty-three impulsive and 15 nonimpulsive alcoholic offenders and 21 healthy volunteers were studied in the forensic psychiatry ward of a university psychiatric department. The subjects underwent lumbar punctures and oral glucose and aspartame challenges, and their diurnal activity rhythm was measured with physical activity monitors. Discriminant function analyses were used to investigate psychophysiological and biochemical concomitants of aggressive and impulsive behaviors.

RESULTS

Alcoholic, impulsive offenders with antisocial personality disorder had low mean cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) and corticotropin levels and high mean CSF testosterone concentrations. Compared with healthy volunteers, they showed increased physical activity during the daytime. Alcoholic, impulsive offenders with intermittent explosive disorder had a low mean CSF 5-HIAA concentration and blood glucose nadir after an oral glucose challenge, and desynchronized diurnal activity rhythm. Healthy volunteers had mean CSF 5-HIAA concentrations that were intermediate between those of alcoholic, impulsive and nonimpulsive offenders. Alcoholic, nonimpulsive offenders had a significantly higher mean CSF 5-HIAA concentration than all the other groups, including healthy volunteers.

CONCLUSIONS

In the present sample, a low CSF 5-HIAA concentration was primarily associated with impulsivity and high CSF testosterone concentration, with aggressiveness or interpersonal violence.

Peripheral CRF inhibits gastric emptying and stimulates colonic motor function in rats. We investigated the role of CRF(1) and CRF(2) receptors in i.p. CRF-induced alterations of gut transit in conscious mice using selective CRF(1) and CRF(2) ligands injected i.p. Gastric emptying 2 h after ingestion of a solid chow meal and colonic transit (time to expel a bead inserted into the distal colon) were determined simultaneously. Rat/human (r/h)CRF, which has CRF(1)>> CRF(2) binding affinity, decreased distal colonic transit time at lower doses (6-12 microg/kg) than those inhibiting gastric emptying (20-60 microg/kg). Ovine CRF, a preferential CRF(1) receptor agonist (6-60 microg/kg), reduced significantly the colonic transit time without altering gastric emptying, whereas the selective CRF(2) receptor agonists mouse urocortin II (20-60 microg/kg) and urocortin III (120 microg/kg) inhibited significantly gastric emptying without modifying colonic transit. The CRF(1)/CRF(2) receptor antagonist, astressin (30-120 microg/kg), dose dependently prevented r/hCRF (20 microg/kg)-induced inhibition of gastric emptying and reduction of colonic transit time. The selective CRF(1) receptor antagonists, NBI-27914 (C(18)H(20)Cl(4)N(4)C(7)H(8)O(3)S) and CP-154,526 (butyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]ethylamine) (5-30 mg/kg), dose dependently blocked r/hCRF action on the colon without influencing the gastric response, whereas the CRF(2) receptor antagonist, antisauvagine-30 (30-100 microg/kg), dose dependently abolished r/hCRF-induced delayed gastric emptying and had no effect on colonic response. These data show that i.p. r/hCRF-induced opposite actions on upper and lower gut transit in conscious mice are mediated by different CRF receptor subtypes: the activation of CRF(1) receptors stimulates colonic propulsive activity, whereas activation of CRF(2) receptors inhibits gastric emptying.

The effect of intracerebroventricular injection of the mitosis inhibitor colchicine and of immobilization stress, subcutaneous injection of capsaicin, and intraperitoneal injection of hypertonic salt solution on expression of c-Fos-like immunoreactivity was studied in the rat brain with immunohistochemistry. All the procedures induced c-Fos immunoreactivity in parvocellular neurons of the paraventricular nucleus, and many of these neurons also contained corticotropin-releasing factor immunoreactivity. c-Fos immunoreactivity was also observed, for example, in subpopulations of neurons in the locus coeruleus, the ventrolateral medulla oblongata, and the nucleus tractus solitarii. Many of these cells also expressed catecholamine-synthesizing enzymes. The results suggest that intraventricular injection of colchicine is a stressful stimulus and support the view that several catecholamine cell groups in the lower brainstem are part of the brain circuitry mediating stress reactions, as are the hypothalamic neurons that contain corticotropin-releasing factor.

Alcohol dependence is characterized by excessive consumption, loss of control over intake and the presence of a withdrawal syndrome, including both motivational and physical symptoms. Previous studies have implicated the brain corticotropin-releasing factor (CRF) stress systems in mediating the negative emotional state associated with ethanol withdrawal. CRF(1) receptor-specific antagonists, administered systemically, and CRF receptor subtype nonspecific antagonists, administered into the central nucleus of the amygdala (CeA), selectively decrease the anxiety-like behaviors and increased ethanol self-administration associated with ethanol withdrawal. In the present study, we investigated the role of CRF(2) receptors within the CeA in mediating ethanol self-administration in ethanol-dependent and nondependent animals. Male Wistar rats were made dependent on ethanol using an intermittent ethanol vapor exposure paradigm. Nondependent animals received similar conditions but were exposed to air only. Following 2 h of withdrawal from ethanol vapors, ethanol and water self-administration were measured following administration of urocortin 3, a highly selective CRF(2) agonist, in the CeA. In dependent rats, urocortin 3 (0.1 microg/microl and 0.5 microg/microl) decreased ethanol self-administration, with no effect on water self-administration. In nondependent rats, urocortin 3 (0.5 microg/microl) increased ethanol self-administration, with no effect on water self-administration. These data demonstrate an opposing role of the CRF(2) receptor subtype within the CeA in mediating ethanol self-administration in withdrawn, dependent and nondependent rats.

As a hormone in the hypothalamic-pituitary-adrenocortical (HPA) axis corticotropin-releasing factor (CRF) mediates stress responses. CRF can also act as a neuromodulator of synaptic transmission outside the HPA axis. A major site of extrahypothalamic expression of CRF and its G-protein-coupled receptors is the amygdala, a key player in affect-related disorders such as anxiety. The laterocapsular division of the central nucleus of the amygdala (CeLC) is important for the modulation of pain affect. This study determined the effects of CRF1 and CRF2 receptor antagonists in CeLC neurons in an arthritis pain model. Extracellular single-unit recordings were made from CeLC neurons in anesthetized adult rats. All neurons responded more strongly to noxious than to innocuous mechanical stimulation (compression) of peripheral tissues, including the knee. Evoked responses and background activity were measured before and during the development of a kaolin/carrageenan-induced knee joint arthritis. Drugs were administered into the CeLC by microdialysis before and/or after arthritis induction. All CeLC neurons showed increased responses to mechanical stimuli ("sensitization") 5-6 h postinduction of arthritis. A selective CRF1 receptor antagonist (NBI27914; 1-100 microM, concentration in microdialysis probe; 15 min) inhibited evoked responses and background activity in arthritis (n = 9) but had no effect under normal conditions before arthritis (n = 9). In contrast, a selective CRF2 receptor antagonist (Astressin-2B; 1-100 microM, 15 min) had no effect in arthritis (n = 7) but increased the neurons' responses under normal conditions (n = 8). These data suggest that CRF1 receptors in the amygdala contribute to pain-related sensitization, whereas the normally inhibitory function of CRF2 receptors is lost in the arthritis pain model.

The search for novel drugs for treating psychiatric disorders is driven by the growing medical need to improve on the effectiveness and side-effect profile of currently available therapies. Given the wealth of preclinical data supporting the role of neuropeptides in modulating behaviour, pharmaceutical companies have been attempting to target neuropeptide receptors for over two decades. However, clinical studies with synthetic neuropeptide ligands have been unable to confirm the promise predicted by studies in animal models. Here, we analyse preclinical and clinical results for neuropeptide receptor ligands that have been studied in clinical trials for psychiatric diseases, including agents that target the receptors for tachykinins, corticotropin-releasing factor, vasopressin and neurotensin, and suggest new ways to exploit the full potential of these candidate drugs.

We examined whether corticotropin-releasing factor (CRF) was involved in orexin-induced grooming and face-washing behaviors, and whether orexin was involved in the stress reaction. Administration of alpha-helical CRF, CRF antagonist, alone had no behavioral effect, but it blocked the orexin-induced grooming and face-washing behaviors in rats. The level of corticosterone increased in a dose-dependent manner 15 min after icv injection of orexin, and it remained high for at least 60 min. In 2-month-old rats, 1 h of immobilization stress increased orexin mRNA levels, but not the melanin-concentrating hormone (MCH) mRNA, in the lateral hypothalamic area (LHA). In 6-month-old rats, 30 min of cold stress increased the expression of orexin mRNA in the LHA. Unlike in the 2-month-old rats, immobilization stress did not change orexin mRNA expression in 6-month-old rats. These results suggest that CRF is involved in orexin-induced behaviors, and that orexin may play an important role in some stress reactions.

It has been previously documented that human skin cells including epidermal keratinocytes and dermal fibroblasts produce and process proopiomelanocortin (POMC), corticotropin releasing hormone (CRH), and express functional CRH receptors type-1 (CRH-R1). The skin also has corticosteroidogenic activity, suggesting a functional connection between these elements. In the current study, we found that human dermal fibroblasts (but not normal epidermal keratinocytes) respond to CRH with stimulation of cAMP, with POMC gene and protein expression, and ACTH production and release. Furthermore, CRH and ACTH stimulate production of corticosterone in fibroblasts, with ACTH being more potent. Although cortisol-immunoreactivity accumulation/production in fibroblasts has been detected by ELISA, it appears to be constitutive (not affected by CRH or ACTH). These effects are absent in keratinocytes. Therefore, we propose that fibroblasts but not keratinocytes display a functional CRH-POMC-corticosteroid axis organized similarly to the hypothalamus-pituitary-adrenal (HPA) axis. However, it diverges from the HPA organization in its distal step, where CRH and ACTH stimulate production of corticosterone, instead of cortisol.

Previous studies have reported elevated concentrations of cerebrospinal fluid (CSF) corticotropin-releasing factor (CRF) in patients with major depression. Elevations of CSF CRF have also been reported in adult laboratory animals exposed to the stress of brief maternal deprivation or maternal neglect in the neonatal or preweaning period. The present study was designed to determine whether major depression and a history of perceived early adversity in childhood are independently associated with elevated CSF CRF concentrations in adults. In this case-control study, 27 medication-free adults with major depression and 25 matched controls underwent standardized lumbar puncture for collection of a single CSF sample at 1200. Subjects provided data about significant adverse early-life experiences and rated their global perceived level of stress during pre-school and preteen years on a six-point Likert scale. The mean difference in CSF CRF between depressed patients and controls did not reach statistical significance. In a regression model, perceived early-life stress was a significant predictor of CSF CRF, but depression was not. Perinatal adversity and perceived adversity in the preteen adversity years (ages 6-13 years) were both independently associated with decreasing CSF CRF concentrations. The relationship observed between perceived early-life stress and adult CSF CRF concentrations in this study closely parallels recent preclinical findings. More work is needed to elucidate the critical nature and timing of early events that may be associated with enduring neuroendocrine changes in humans.

Corticotropin-releasing factor (CRF) acts within the locus coeruleus (LC), to modulate activity of the LC-norepinephrine (NE) system. Combining molecular and cellular approaches, we demonstrate CRF receptor (CRFr) mRNA expression in Sprague-Dawley rat LC and provide the first in vivo evidence for agonist-induced internalization of CRFr. CRFr mRNA was detected in LC micropunches by RT-PCR. In dual labelling immunofluorescence studies, tyrosine hydroxylase (TH) containing neurons exhibited CRFr labelling. At the ultrastructural level, immunogold-silver labelling for CRFr was localized to the plasma membrane of TH-immunoperoxidase labelled dendrites. CRF (100 ng) injection into the LC produced a robust neuronal activation that peaked 10-15 min after injection and was maintained for the duration of the recording. This was associated with CRFr internalization in LC neurons that was apparent at 5 and 30 min after injection. By 5 min after injection the ratio of cytoplasmic to total dendritic CRFr-labelling was 0.81 +/- 0.01 in rats injected with CRF and 0.59 +/- 0.02 in rats injected with artificial cerebrospinal fluid (ACSF; P < 0.0001). Enhanced internalization of CRFr was maintained at 30 min after CRF injection, with the ratio being 0.86 +/- 0.02 for CRF-injected cases and 0.57 +/- 0.03 for ACSF-injected cases (P < 0.0001). Internalized CRFr was associated with early endosomes, indicative of degradation or recycling. Agonist-induced CRFr internalization in LC neurons may underlie acute desensitization to CRF or stress. This process may be a pivotal target by which stressors or pharmacological agents regulate the sensitivity of the LC-NE system to CRF and subsequent stressors.

Immunohistochemical detection of the immediate-early gene c-fos was used to determine the pattern of neuronal activity in the rat brain after exposure to water-avoidance stress known to stimulate fecal output in rats. Avoidance to water for 1 h by standing on a small platform increases pellet output and induces numerous Fos-positive cells in the parvocellular part of the paraventricular nucleus of the hypothalamus (PVN), locus coeruleus (LC) and, to a lesser extent, in the bed nucleus of the stria terminalis, lateral septum, dorsal raphe nucleus and A5 and A1 noradrenergic neurons. The corticotropin-releasing factor (CRF) antagonist, alpha-helical CRF9-41 (50 micrograms i.c.v.) reduced water-avoidance stress-induced c-fos expression mainly in the PVN and the LC (44 and 60%, respectively) and decreased by 60% the stimulated fecal output. These data indicate that water-avoidance stress activates PVN and LC neurons through CRF pathways which contribute to the stimulation of colonic motor function.

A polymorphism in the mu-opioid receptor (MOR) (A118G) has been shown to increase beta-endorphin binding affinity, theoretically placing greater inhibitory tone on hypothalamic corticotropin-releasing hormone (CRH) neurons. We hypothesized that the minor allele (G) would predict cortisol responses to both pharmacological (naloxone) and psychological (stress) activation of the hypothalamic-pituitary-adrenal (HPA) axis. Healthy subjects (mean age 25.2 years, SD 9.2 years) completed a naloxone challenge (n=74) and/or the modified Trier Social Stress Test (TSST) (n=86). For the naloxone challenge, two baseline blood samples were obtained. Then, five increasing doses of i.v. naloxone were administered at 30-min intervals and 12 additional blood samples were collected at 15-min intervals. The TSST consisted of 5-min of public speaking and 5-min of mental arithmetic exercises. Three baseline and five post-TSST blood samples were drawn. Both the naloxone and TSST groups had significant adrenocorticotropin (ACTH) and cortisol responses to their respective challenges (P<0.001). There were no differences in baseline ACTH, baseline cortisol, or ACTH response by genotype in either the naloxone or the TSST group. Among subjects expressing a G allele, there was a higher cortisol response to naloxone (P=0.046), but a lower cortisol response to the TSST (P=0.044). In conclusion, the minor allele (G) was associated with a robust cortisol response to naloxone blockade, but a blunted response to psychosocial stress. We speculate that increased opioid avidity of the minor allele receptor contributes to the differential response to naloxone vs stress.

Over the past 40 years, it has been recognised that the maternal hypothalamic-pituitary-adrenal (HPA) axis undergoes adaptations through pregnancy and lactation that might contribute to avoidance of adverse effects of stress on the mother and offspring. The extent of the global adaptations in the HPA axis has been revealed and the underlying mechanisms investigated within the last 20 years. Both basal, including the circadian rhythm, and stress-induced adrenocorticotrophic hormone and glucocorticoid secretory patterns are altered. Throughout most of pregnancy, and in lactation, these changes predominantly reflect reduced drive by the corticotropin-releasing factor (CRF) neurones in the parvocellular paraventricular nucleus (pPVN). An accompanying profound attenuation of HPA axis responses to a wide variety of psychological and physical stressors emerges after mid-pregnancy and persists until the end of lactation. Central to this suppression of stress responsiveness is reduced activation of the pPVN CRF neurones. This is consequent on the reduced effectiveness of the stimulation of brainstem afferents to these CRF neurones (for physical stressors) and of altered processing by limbic structures (for emotional stressors). The mechanism of reduced CRF neurone responses to physical stressors in pregnancy is the suppression of noradrenaline release in the PVN by an up-regulated endogenous opioid mechanism, which is induced by neuroactive steroid produced from progesterone. By contrast, in lactation suckling the young provides a neural stimulus that dampens the HPA axis circadian rhythm and reduces stress responses. Reduced noradrenergic input activity is involved in reduced stress responses in lactation, although central prolactin action also appears important. Such adaptations limit the adverse effects of excess glucocorticoid exposure on the foetus(es) and facilitate appropriate metabolic and immune responses.

We report the discovery of a new CRF2 receptor splice isoform found in human brain, which we have termed the CRF2gamma receptor. The CRF2gamma cDNA encodes for a 397-amino acid receptor that has an amino terminus with no significant homology to the already reported alpha- and beta-termini. When expressed in 293-EBNA (Epstein-Barr nuclear antigen) cells, the CRF2gamma receptor responds in a dose-dependent manner to CRF and related peptides with a rank order of potency of urocortin>> or = sauvagine>urotensin>r/h CRF, with EC50 values more similar to CRF2alpha than CRF2beta. Equilibrium saturation isotherm analysis with radiolabeled sauvagine reveals a two site/state model for binding to CRF2gamma with a 60 pM Kd high-affinity site and a 5 nM Kd low-affinity site. Analysis of CRF2gamma RNA expression in human brain demonstrates expression in septum and hippocampus, with weaker but detectable expression in amygdala, nucleus accumbens, midbrain, and frontal cortex.

Sebaceous glands may be involved in a pathway conceptually similar to that of the hypothalamic-pituitary-adrenal (HPA) axis. Such a pathway has been described and may occur in human skin and lately in the sebaceous glands because they express neuropeptide receptors. Corticotropin-releasing hormone (CRH) is the most proximal element of the HPA axis, and it acts as central coordinator for neuroendocrine and behavioral responses to stress. To further examine the probability of an HPA equivalent pathway, we investigated the expression of CRH, CRH-binding protein (CRH-BP), and CRH receptors (CRH-R) in SZ95 sebocytes in vitro and their regulation by CRH and several other hormones. CRH, CRH-BP, CRH-R1, and CRH-R2 were detectable in SZ95 sebocytes at the mRNA and protein levels: CRH-R1 was the predominant type (CRH-R1/CRH-R2 = 2). CRH was biologically active on human sebocytes: it induced biphasic increase in synthesis of sebaceous lipids with a maximum stimulation at 10(-7) M and up-regulated mRNA levels of 3 beta- hydroxysteroid dehydrogenase/Delta(5-4) isomerase, although it did not affect cell viability, cell proliferation, or IL-1 beta-induced IL-8 release. CRH, dehydroepiandrosterone, and 17 beta-estradiol did not modulate CRH-R expression, whereas testosterone at 10(-7) M down-regulated CRH-R1 and CRH-R2 mRNA expression at 6 to 24 h, and growth hormone (GH) switched CRH-R1 mRNA expression to CRH-R2 at 24 h. Based on these findings, CRH may be an autocrine hormone for human sebocytes that exerts homeostatic lipogenic activity, whereas testosterone and growth hormone induce CRH negative feedback. The findings implicate CRH in the clinical development of acne, seborrhea, androgenetic alopecia, skin aging, xerosis, and other skin disorders associated with alterations in lipid formation of sebaceous origin.

The promoter regions of the rat corticotropin-releasing factor (CRF), oxytocin (OT), and vasopressin (AVP) genes contain sequences similar to the cis-acting response element identified for NGFI-B, an immediate-early gene structurally related to the steroid hormone receptor superfamily. Combined immuno- and hybridization histochemical approaches were used to determine whether challenges that influence the synthesis and secretion of CRF, OT, and/or AVP result in altered expression in neurosecretory neurons of NGFI-B and another immediate-early gene, c-fos, which is widely used as a marker for functionally activated neurons. NGFI-B mRNA was found to be expressed at constitutively high levels in the telencephalon, but not in the endocrine hypothalamus, of unperturbed controls; basal levels of c-fos expression were uniformly low throughout the CNS. NGFI-B and c-fos mRNAs, and Fos protein, were induced with a similar time course and in similar neuroendocrine cell types in response to acute hypotensive hemorrhage (15% reduction in blood volume), intravenous injection of interleukin-1 beta (IL-1 beta; 1.87 micrograms/kg), chronic salt loading (7 d maintenance on 2% saline), and acute bilateral adrenalectomy. c-fos mRNA and Fos protein were readily demonstrable in afferent pathways that have been implicated as mediating the neuroendocrine responses in the three stress paradigms; these include medullary catecholaminergic cell groups in response to IL-1 beta and hemorrhage, and cell groups lining the lamina terminalis in response to salt loading. Challenge-specific induction of NGFI-B expression was detectable in these extrahypothalamic cell groups, though with a lesser sensitivity than that required to reveal NGFI-B induction in the hypothalamus, or c-fos expression in these related afferents. These results establish NGFI-B as a useful adjunct to c-fos, for revealing synaptic and/or transcriptional activation in the magno- and parvocellular neurosecretory systems. Differences in the sensitivity of the two markers in revealing functionally related activation in extrahypothalamic regions speak to general issues concerning the use of immediate-early genes in mapping functional circuitry in the CNS.

A clonal cell line that responds to insulin and to lipolytic hormones has been established from the epididymal fat pad of the C57BL/6J ob/ob mouse. This line, designated ob 17, has a doubling time of 12.5 or 19 hr in 10% or 1% fetal calf serum, respectively. It presents a heterogeneous chromosome number with 40% of the cells containing 35-44 chromosomes and expresses the characteristic H2-LA antigen. After cessation of growth, ob 17 cells accumulate droplets of triglycerides; this accumulation occurs to a significant extent even in the absence of insulin normally added after confluence. Lipoprotein lipase activity is negligible in exponentially growing cells but appears at its maximal level just after confluence with or without insulin. Acid:CoA ligase and acylCoA:diglyceride acyltransferase develop later than lipoprotein lipase. The appearance of lipolytic and lipogenic enzymes, but not of triglycerides, seems to be independent of the presence of lipoproteins or of unesterified fatty acids in the culture medium. Therefore, the differentiation program becomes operative when growth is arrested, and differentiation occurs, providing a source of exogenous lipids. Differentiated ob 17 cells in which endogenous triglycerides have been prelabeled on the fatty acid moiety do respond to epinephrine and corticotropin by release of radioactive fatty acid. This lipolytic response is counteracted by prior addition of insulin. The ob 17 cell line appears to be a useful model for study of growth and differentiation of adipose cells as compared to preadipocyte cell lines from the nongenetically obese mouse.

Corticotropin-releasing factor (CRF) has behavioral activating effects when injected intracerebroventricularly in rats. CRF dose-dependently increased activity in a familiar photocell cage environment. This activation persisted after hypophysectomy, opiate receptor blockade, and low-dose dopamine receptor blockade, which suggests a unique mechanism of action. CRF also improved acquisition of a visual discrimination task. In aversive situations such as an open field test CRF produced behavioral changes consistent with increased emotionality. These results suggest that CRF liberated directly into the central nervous system may have a neurotropic action important for mobilizing behavioral responses to stress.

A growth-hormone-releasing factor has been characterised and sequenced from a pancreatic tumour removed from a patient with acromegaly. It is a 40-residue linear peptide. Synthetic human pancreatic growth-hormone-releasing factor (hpGRF-40), 1 microgram/kg bodyweight, was administered as an intravenous bolus to six healthy men. hpGRF-40 selectively stimulated growth-hormone secretion. Serum growth-hormone concentrations were increased within 5 min, reaching a peak between 30 and 60 min (20 . 4 +/- 6 . 5 ng/ml compared with 2 . 1 +/- 0 . 1 ng/ml after placebo). Serum levels of prolactin, thyrotropin, luteinising hormone, and corticotropin (measured indirectly through plasma cortisol) were not increased after administration of hpGRF-40. Similarly, the concentrations of blood glucose, plasma insulin, glucagon, pancreatic polypeptide, cholecystokinin, gastrin, gastric inhibitory peptide, motilin, and somatostatin were unaffected by hpGRF-40. There were no changes in blood pressure, pulse rate, or body temperature, and no side-effects were noted. The characteristics of this peptide fulfil many of the criteria required of the hypophysiotropic growth-hormone-releasing hormone. hpGRF holds promise for a new approach to the diagnosis and treatment of various disorders of growth-hormone secretion.

The purpose of the study was to determine the specific periods during pregnancy in which human fetal exposure to stress hormones affects newborn physical and neuromuscular maturation. Blood was collected from 158 women at 15, 19, 25, and 31 weeks' gestation. Levels of placental corticotropin-releasing hormone (CRH) and maternal cortisol were determined from plasma. Newborns were evaluated with the New Ballard Maturation Score. Results indicated that increases in maternal cortisol at 15, 19, and 25 weeks and increases in placental CRH at 31 weeks were significantly associated with decreases in infant maturation among males (even after controlling for length of gestation). Results also suggested that increases in maternal cortisol at 31 weeks were associated with increases in infant maturation among females, although these results were not significant after controlling for length of gestation. Findings suggest that stress hormones have effects on human fetal neurodevelopment that are independent of birth outcome.

Studies of the ontogeny of immunity in a limited number of representative amphibians have shown that while the immune systems of the larval forms are competent to defend against potential pathogens in the temporary ponds they inhabit, they are not equivalent to the mature immune systems that develop after metamorphosis. Metamorphosis is a critical time of transition when increased concentrations of metamorphic hormones, principally thyroid hormones (TH) and corticosteroid hormones (CH), orchestrate the loss or reorganization of many tissues and organ systems, including the immune system. Immune system reorganization may serve to eliminate unnecessary lymphocytes that could be destructive if they recognized newly emerging adult-specific antigens on the adult tissues. Increased corticosteroids during metamorphosis appear to induce apoptosis of susceptible lymphocytes. This cell death can be inhibited in vitro or in vivo by the corticosteroid receptor antagonist, RU486. A coordinate increase in both TH and CH at metamorphosis may be common to all amphibians that undergo metamorphosis. Current evidence suggests that the central hypothalamic mediator that induces pituitary production of both thyroid-stimulating hormone and adrenocorticotropic hormone in larval amphibians is corticotropin-releasing hormone. Most amphibians probably survive the temporary immunosuppression associated with metamorphosis with no deleterious effects. However, it is hypothesized that if environmental stressors result in the induction of metamorphosis at a less than optimal body size and state of immune maturation, the immune system destruction would be more significant, and the amphibians could be at greater risk of infection and death.

Corticotropin-releasing hormone (CRH) excites hippocampal neurons and induces death of selected CA3 pyramidal cells in immature rats. These actions of CRH require activation of specific receptors that are abundant in CA3 during early postnatal development. Given the dramatic effects of CRH on hippocampal neurons and the absence of CRH-containing afferents to this region, we hypothesized that a significant population of CRHergic neurons exists in developing rat hippocampus. This study defined and characterized hippocampal CRH-containing cells by using immunocytochemistry, ultrastructural examination, and colocalization with gamma-aminobutyric acid (GABA)-synthesizing enzyme and calcium-binding proteins. Numerous, large CRH-immunoreactive (ir) neurons were demonstrated in CA3 strata pyramidale and oriens, fewer were observed in the corresponding layers of CA1, and smaller CRH-ir cells were found in stratum lacunosum-moleculare of Ammon's horn. In the dentate gyrus, CRH-ir somata resided in the granule cell layer and hilus. Ultrastructurally, CRH-ir neurons had aspiny dendrites and were postsynaptic to both asymmetric and symmetric synapses. CRH-ir axon terminals formed axosomatic and axodendritic symmetric synapses with pyramidal and granule cells. Other CRH-ir terminals synapsed on axon initial segments of principal neurons. Most CRH-ir neurons were coimmunolabeled for glutamate decarboxylase (GAD)-65 and GAD-67 and the majority also contained parvalbumin, but none were labeled for calbindin. These results confirm the identity of hippocampal CRH-ir cells as GABAergic interneurons. Further, a subpopulation of neurons immunoreactive for both CRH and parvalbumin and located within and adjacent to the principal cell layers consists of basket and chandelier cells. Thus, axon terminals of CRH-ir interneurons are strategically positioned to influence the excitability of the principal hippocampal neurons via release of both CRH and GABA.