Corticotropin-releasing Factor Levels Research Articles

Gene expression profiles highlight adaptive brain mechanisms in corticotropin releasing factor overexpressing mice

Corticotropin-releasing factor (CRF) plays an important role in mediating central and peripheral responses to stress. Alterations in CRF system activity have been linked to a number of psychiatric disorders, including anxiety and depression. Aim of this study was to elucidate homeostatic mechanisms induced by lifelong elevated CRF levels in the brain. We therefore profiled gene expression in several brain areas of transgenic mice overexpressing CRF (CRF-OE), a model for chronic stress. Several genes showed altered expression levels in CRF-OE mice when compared to their wild type littermates and were confirmed by quantitative PCR. Differences in gene expression profiles revealed the presence of previously unrecognized homeostatic mechanisms in CRF-OE animals. These included changes in glucocorticoid signaling, as exemplified by changes in 11β-hydroxysteroid dehydrogenase type 1, FK506 binding protein 5 and serum/glucocorticoid kinase. Alterations in expression of genes involved in myelination (myelin, myelin-associated glycoprotein), cell proliferation and extracellular matrix formation (Edg2, Fgfr2, decorin, brevican) suggest changes in the dynamics of neurogenesis in CRF-OE. Pronounced changes in neurotensin (NT) receptors 1 and 2 mRNA were identified. Overall downregulation of NT receptors in CRF-OE animal was substantiated by receptor binding studies. Pronounced neurotensin receptor downregulation was observed for NT type 1 receptors in limbic brain areas, suggesting that NT could be implicated in some of the effects attributed to CRF overexpression. These data show that lifelong exposure to excessive CRF leads to adaptive changes in the brain which could play a role in some of the behavioral and physiological alterations seen in these animals.

Stress induces CRF release in the paraventricular nucleus, and both CRF and GABA release in the amygdala

In the hypothalamus, corticotropin-releasing factor (CRF) initiates the hypothalamic–pituitary–adrenal (HPA) axis response to stress, resulting in the release of glucocorticoids, including cortisol. Extrahypothalamic CRF, particularly in the limbic system, also appears to play a role in the stress response. To further define brain CRF response to stress, immunosensor-based microdialysis probes were used to measure the extracellular levels of CRF in the paraventricular nucleus of the hypothalamus (PVN) and in the amygdala of sheep during a predator (dog) exposure stress. In addition, gamma amino butyric acid (GABA) was measured in the amygdala and cortisol was measured in venous blood. Exposure to the predator stress increased CRF in the PVN and both CRF and GABA in the amygdala. These were followed in time by a rise in venous cortisol. Application of a CRF antagonist to the amygdala, immediately prior to stress, had a small effect on the subsequent observed stress responses. This treatment, however, significantly reduced the responses to a repeat stress administered 2 days later, compared to nontreated animals. Application of a GABA antagonist to the amygdala prior to stress had no effect on the subsequent observed stress response but increased the response to the stress repeated 2 days later. Perfusion with 4-aminopyridine, a neuronal depolarising agent, into the PVN induced a release of CRF accompanied shortly thereafter by a small increase in CRF in the amygdala, and 5–10 min later by an increase in venous cortisol. Perfusion into the amygdala increased the levels of both CRF and GABA but had no effect on either PVN CRF or venous cortisol. These data support roles for both the PVN and amygdala in stress responsiveness. It suggests further that actions at the amygdala can strongly influence subsequent responsiveness to a further stress, mediated in part by both CRF and GABA actions.

Prenatal exposure to interleukin-6 results in hypertension and increased hypothalamic-pituitary-adrenal axis activity in adult rats.

During pregnancy, systemic inflammatory responses induce cytokines that may stress the fetus and contribute to cardiovascular and neuroendocrine dysfunction in adulthood. We evaluated the effects of early and late prenatal exposure to IL-6 on mean systolic arterial pressure (MSAP) and hypothalamic-pituitary-adrenal (HPA) axis regulation in male and female rats at 5-24 wk of age. MSAP and ACTH and corticosterone levels were measured basally and in response to a novel environment, immobilization stress, and stimulation with corticotropin-releasing factor (CRF) and ACTH. In addition, mRNA expression and protein levels of glucocorticoid receptor, mineralocorticoid receptor, CRF receptor type 1, and CRF were estimated in brain areas thought to mediate central effects of corticosteroids on the HPA axis and on central neuroendocrine regulation of MSAP. Both early and late prenatal IL-6 exposure led to hypertension, which was evident in females at 5 wk of age. In adult rats, basal ACTH and corticosterone levels were elevated, the responses to stress and stimulation tests were of extended duration, and circadian rhythm during the light period was flattened and reversed. Mineralocorticoid receptor and glucocorticoid receptor mRNA expression was reduced in the hippocampus, the CRF level was increased in the hypothalamus, and CRF receptor type 1 mRNA expression was increased in the pituitary. These findings suggest that fetal stress induced by prenatal exposure to IL-6 leads to hypertension and dysregulation of HPA axis activity during adulthood.

Cocaine- and amphetamine-regulated transcript activates the hypothalamic-pituitary-adrenal axis through a corticotropin-releasing factor receptor-dependent mechanism.

Cocaine- and amphetamine-regulated transcript (CART) is a highly expressed hypothalamic transcript that is concentrated in areas associated with the stress response. There is evidence for a role of CART in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis. However, it is not clear whether CART regulates activity of the HPA axis by directly stimulating ACTH release from pituitary corticotropes or through interaction with hypothalamic factors. To address this issue, the effects of central and peripheral administration of CART on the HPA axis were compared. Central administration of CART(55-102) (1 microg) significantly increased circulating levels of ACTH (481 +/- 122 vs. 93 +/- 14 pg/ml; CART vs. vehicle) and corticosterone (460 +/- 29 vs. 179 +/- 62 ng/ml; CART vs. vehicle). In contrast, iv injection of CART(55-102) (0.09-9.0 nmol/kg) did not significantly affect circulating levels of ACTH or corticosterone. The corticotropin-releasing factor (CRF) receptor antagonist Astressin B was used to determine whether CART(55-102) elicits ACTH secretion via a CRF receptor-dependent mechanism. Injection of Astressin B (50 microg/kg, iv) inhibited CART(55-102)-induced ACTH and corticosterone responses. The effects of CART(55-102) on CRF and arginine vasopressin (AVP) expression were also examined in static hypothalamic explants. RT-PCR analysis revealed a significant up-regulation of CRF and AVP mRNA levels after CART(55-102) (10 nm and 1 microm) treatment. Last, the effects of CART(55-102) on CRF- and AVP-mediated ACTH release was investigated in dispersed rat anterior pituitary cells. Incubation of CART(55-102) (10-100 nm) did not significantly affect ACTH release from anterior pituitary cells. Findings from the present study suggest that CART regulates activity of the HPA axis through a CRF-dependent central mechanism and not by means of direct interaction with pituitary corticotropes.

Elevated Blood Lactate Is Not a Primary Causeof Anorexia in Tumor-Bearing Rats

Tumor-bearing (TB) rats exhibit elevated concentrations of lactate in blood contiguous with the development of anorexia. Continuous intravenous infusion of lactate into non-TB rats reduced food intake at plasma concentrations lower than those observed in anorectic TB rats. Levels of neuropeptide Y (NPY) were elevated in the ventromedial (VMH) and dorsomedial hypothalamic regions of lactate-infused rats. The addition of the enhancer of pyruvate dehydrogenase activity, dichloroacetate (DCA), to the drinking water of TB rats (0.1-0.4%) normalized blood lactate concentration but had no significant effect on anorexia. However, the elevated concentration of NPY in the VMH of anorectic TB rats was also normalized by the DCA treatment. No alterations in regional hypothalamic levels of corticotropin-releasing factor were observed within any treatment conditions. These results suggest that, although hyperlactatemia may be involved in maintaining elevated NPY concentrations in anorectic TB rats, it does not appear to be a significant factor in the etiology of experimental cancer anorexia.

Effects of Early-Life Stress on CRF in Adult Humans

For decades, researchers have studied depression, stress, and associated changes in the hypothalamic-pituitary-adrenal (HPA) axis. Levels of the brain peptide corticotropin-releasing factor (CRF) become elevated in animals responding to stress; adult animals exposed to early developmental stress exhibit altered CRF levels and behavioral-stress responsivity. More recent studies in adult humans show that early-life stress …

Inflammatory response to cardiac bypass in ewe fetuses: effects of steroid administration or continuous hemodiafiltration

Objectives We sought to investigate the effectiveness of glucocorticoid administration or continuous venovenous hemodiafiltration on endothelin and corticotropin-releasing factor release or clearance during prolonged fetal cardiac bypass and on the overall performance of fetuses. Methods Circulating endothelin 1, 2, and 3 and corticotropin-releasing factor levels were measured in fetal ewes during a 60-minute cardiac bypass period performed with an inline axial flow pump. Blood samples were collected before, during, and 90 minutes after cardiac bypass. Animals were divided into 4 groups. The betamethasone group (n = 6) received maternal treatment with 12 mg of betamethasone 1 and 2 days before the experiment. The methylprednisolone group (n = 5) received fetal treatment with 40 mg/kg intravenous methylprednisolone at the beginning of cardiac bypass. The continuous venovenous hemodiafiltration group (n = 4) underwent continuous venovenous hemodiafiltration with a 0.3-m 2 polysulfone filter during cardiac bypass. The final group was the control group (n = 4). Results Maternal steroid pretreatment failed to decrease endothelin or corticotropin-releasing factor production when compared with levels in the control animals. Fetal treatment with methylprednisolone produced a significant decrease in endothelin 2 production during cardiac bypass ( P < .02) and endothelin 1 production at the end of the experiment ( P < .02). Continuous venovenous hemodiafiltration blocked completely the increase of endothelin and corticotropin-releasing factor levels during cardiac bypass ( P < .02), which was maintained 90 minutes after cardiac bypass. Acid-base balance was preserved during cardiac bypass by the continuous venovenous hemodiafiltration but worsened after disconnection of the extracorporeal circuit, whereas animals treated with methylprednisolone had better pH, Pa co 2, and bicarbonate levels by the end of the experiment. The overall tolerance of the procedure was better in the continuous venovenous hemodiafiltration group during cardiac bypass and in the methylprednisolone group at the end of the experiment. Conclusions Continuous venovenous hemodiafiltration provides sustained stability of endothelin levels during fetal cardiac bypass. This technique might help, in association with fetal steroid treatment, to contain the inflammatory response leading to postbypass placental dysfunction.

Corticotropin-releasing factor in posttraumatic stress disorder (PTSD) with secondary psychotic symptoms, nonpsychotic PTSD, and healthy control subjects

BackgroundRecent studies have reported a high comorbidity between posttraumatic stress disorder (PTSD) and psychotic symptoms, and it has been hypothesized that PTSD with comorbid psychosis is a severe form of PTSD. Few studies have examined the neurobiology of PTSD with comorbid psychosis. If PTSD with secondary psychotic symptoms (PTSD-SP) is a severe form of PTSD, then it might be expected to show more extreme perturbations in the neuroendocrine patterns that characterize PTSD. MethodsPatients with PTSD with secondary psychotic symptoms (PTSD-SP), PTSD without psychosis, and healthy comparison subjects were compared for differences in cerebrospinal fluid concentrations of corticotropin-releasing factor (CRF) and somatotropin-release-inhibiting hormone (SRIF). ResultsThe PTSD-SP subjects had significantly higher mean levels of CRF than either the PTSD or control subjects (p < .01). The three groups showed similar SRIF levels. ConclusionsThese data implicate abnormalities in the secretion of CRF with the production of secondary psychotic symptoms in PTSD. This finding supports the validity of PTSD-SP as a PTSD subtype and as a severe form of PTSD.

Frequency-dependent expression of corticotropin releasing factor in the rat's cerebellum

Corticotropin releasing factor (CRF), localized in extrinsic afferents in the mammalian cerebellum, is defined as a neuromodulator within cerebellar circuits, and appears to be an essential element in the generation of long term depression, a proposed mechanism for motor learning. These physiological studies are based on exogenous application of CRF and do not address potential mechanisms that may influence endogenous release of the peptide. In the present study, immunohistochemistry was used to analyze changes in the lobular distribution of CRF-like immunoreactivity (LIR). In addition radioimmunoassay (RIA) was used to quantify changes in levels of the peptide in the cerebellum following stimulation of the inferior cerebellar peduncle (ICP) at 10 or 40 Hz or the inferior olivary nucleus (ION) at 1, 5, 10, or 20 Hz. Results indicate that there is a greater distribution of CRF-like-immunolabeled climbing fibers, mossy fibers, and astrocytes in all lobules of the cerebellum that is directly related to stimulation frequency. Maximal effects were elicited with 40 Hz ICP and 5–10 Hz ION stimulation. Quantitatively, the RIA studies indicate that there is a significant increase in CRF levels in the vermis, hemispheres and flocculus that correlates closely with stimulation frequency. In conclusion, stimulation of cerebellar afferents induces a significant change in the distribution and levels of CRF-LIR in climbing fibers, mossy fibers and glial cells. This suggests that the modulatory effects ascribed to CRF may influence a greater number of target neurons when levels of activity in afferent systems is increased.

Impaired uterine artery blood flow at mid gestation and low levels of maternal plasma corticotropin-releasing factor.

Corticotropin-releasing factor (CRF) is a placental neuropeptide that plays a role in the control of uteroplacental blood flow regulation. Because CRF has a relaxant effect on uterine vasculature in pregnant rats, we aimed to evaluate mid-gestation plasma CRF levels in women with impaired uterine artery blood flow. Maternal plasma CRF was assayed by specific radioimmunoassay, and uterine artery resistance index (RI) was assessed by Doppler evaluation at 22-24 weeks' gestation in 55 healthy pregnant women, of whom 24 showed a unilateral or bilateral uterine artery notch, reflecting resistance. Statistical analysis was performed by the Kruskal-Wallis test followed by the post hoc Dunn's test and the Spearman rank test. The mean uterine artery RI was significantly (P <.001) higher in women with a notch than in healthy controls. Mean +/- standard error of the mean maternal plasma CRF levels were significantly lower in women with a unilateral (168.45 +/- 27.5 pg/mL; P <.01) or bilateral (186.07 +/- 34.5 pg/mL; P <.001) uterine artery notch than in healthy control pregnant women (375.06 +/- 21.77 pg/mL). Although no difference was found in CRF levels between patients with a unilateral or bilateral uterine artery notch, a significant inverse correlation was found between the mean RI and maternal plasma CRF levels (Spearman r = -0.6540; 95% confidence interval, -0.7865, -0.4640; P <.001). Reduced levels of circulating CRF were associated with increased uterine artery resistance, which supports the hypothesis that CRF may regulate uterine artery tone at mid gestation.

Impaired Uterine Artery Blood Flow at Mid Gestation and Low Levels of Maternal Plasma Corticotropin-Releasing Factor

Impaired Uterine Artery Blood Flow at Mid Gestation and Low Levels of Maternal Plasma Corticotropin-Releasing Factor

Foster litters prevent hypothalamic-pituitary-adrenal axis sensitization mediated by neonatal maternal separation

Neonatal maternal separation of rat pups has been shown to produce long-term increases in hypothalamic-pituitary-adrenal (HPA) axis responsiveness, elevated levels of hypothalamic corticotropin releasing factor (CRF) mRNA in the hypothalamic paraventricular nucleus (PVN), and enhanced anxiety-like behavior. These effects appear to be at least partially mediated by subtle disruptions in the quality of maternal-pup interactions. This hypothesis was tested by providing half the dams with foster litters during the maternal separation paradigm, so that in those litters, only the pups and not the dams were experiencing a period of separation. The separation protocol took place daily from PND2-14 for either 15 min (HMS15, handled) or 180 min (HMS180, maternal separation). During the period of separation dams were either transferred to adjacent cages without any pups present (HMS15, HMS180) or to cages containing an age-matched foster litter (HMS15F, HMS180F). As adults, the HMS180 progeny exhibited the expected increased expression of CRF mRNA in the PVN, stress hyper-responsiveness to airpuff startle and evidence of impaired feedback both in the CORT response, as well as in response to the dexamethasone suppression test. The HMS180F rats, however, appeared to be resistant to these effects of maternal separation as they demonstrated CRF mRNA levels intermediate between HMS15 and HMS180 rats. Their stress responses and feedback regulation of the HPA axis was comparable to that of the HMS15 rats. GR mRNA was elevated in the cortex of HMS180F rats. Overall, these studies support the thesis that the long-term effects of neonatal maternal separation may largely result from alterations in the quality of maternal care rather than from direct effects of the separation per se on the pups.

Social recognition in mice: Behavioral disruption with ketamine and blockade with antipsychotic drug

Withdrawal anxiety following chronic ethanol exposure is often associated with relapse in recovering alcoholics. It is likely that brain regions regulating anxiety-like behaviors adapt during chronic ethanol exposure to ultimately regulate such behaviors. The central amygdala contains numerous neurotransmitter systems that have been implicated in the regulation of anxiety-like behavior, including corticotropin releasing factor (CRF) and NMDA-type glutamate receptors. Chronic ethanol exposure causes functional adaptations in both CRF and NMDA receptors that are likely to regulate anxiety-like behaviors expressed during withdrawal. However, the molecular mechanisms governing these adaptations remain unexplored. We therefore evaluated these neurotransmitter systems in Sprague–Dawley rats during chronic ingestion of an ethanol-containing liquid diet. Quantitative real-time reverse transcription–PCR demonstrated that preproCRF mRNA was significantly upregulated by chronic ethanol exposure, whereas mRNA expression of CRF binding protein did not change. There were also no significant changes observed in any of the NMDA subunit mRNAs, although there was a trend toward greater NR2A mRNA expression during chronic ethanol exposure. Using Western blotting analysis we measured NMDA receptor subunit protein expression. Chronic ethanol exposure did not affect protein levels of the NR1 and NR2B subunits. Like the mRNA measures, chronic ethanol exposure did influence NR2A protein levels but the effects were modest. Our results demonstrate that NMDA receptor subunit mRNA and protein expressions are not strongly influenced by exposure to chronic ethanol. This suggests that the functional NMDA receptor adaptations identified in previous studies [Roberto, M., Schweitzer, P., Madamba, S. G., Stouffer, D. G., Parsons, L. H., & Siggins, G. R. (2004). Acute and chronic ethanol exposure alter glutamatergic transmission in rat central amygdala: an in vitro and in vivo analysis. J Neurosci 24, 1594–1603] are likely to be mediated by post-translational events. In contrast, enhanced levels of CRF during/after chronic ethanol exposure are likely to be mediated by increased levels of prepro CRF mRNA. Together, our findings suggest that adaptations to chronic ethanol exposure by proanxiety factors expressed in the central nucleus appear to be mediated by distinct cellular and molecular mechanisms.

Lipopolysaccharide (LPS) induced activation of the immune system in control rats and rats chronically exposed to a low level of the organothiophosphate insecticide, acephate

Lipopolysaccharide (LPS), a key inflammatory component of gram-negative bacteria, induces a distinctive pattern of cytokine release that regulates inflammation. An alteration in the LPS response may play a fundamental role in the pathogenesis of a number of inflammatory diseases. Therefore, this study was conducted to determine whether chronic exposure to a low level of acephate (Ace), a commonly used organophosphate insecticide, impaired the LPS response in rats. This study showed that LPS injection in control rats caused (1) a time-dependent increase in blood lymphocyte enumeration and differentiation, and (2) a sequential increase the pro-inflammatory (interleukin-1beta (IL1beta), tumor necrosis factor-alpha (TNFalpha), interferon-gamma (INTgamma), and inducible nitric oxide synthase (iNOS)) and anti-inflammatory (interleukin-4 (IL-4), corticotropin-releasing factor (CRF), and blood corticosterone (Cort)) cytokines. The pro-inflammatory cytokines increased after 30 min, while the anti-inflammatory cytokines increased 3 h after LPS injection. An increase in proinflammatory cytokines increased lymphocyte enumeration and differentiation, while the increase in anti-inflammatory cytokines re-established homeostasis. In comparison to the control rats, the Ace-exposed rats exhibited (1) lower levels of IL1beta, TNFalpha and iNOS, (2) higher levels of CRF and Cort, and (3) lower levels of IL-4 in blood and/or brain samples. The abnormal cytokine production may be associated with abnormal phenotypic distribution of B and T cells. Blood IgMhi IgDhi, IgMlo IgDlo and CD8+ CD45RA- CCR7+ cells were elevated, while IgMlo IgDhi, IgMhi IgDlo, IgMin IgDlo, CD8+ CD45RA+ CCR7+ and CD8+ CD45RA- CCR7 cells were depressed in Ace-exposed rats. Thus, chronic low-level Ace exposure may impair the lineage commitment in lymphocytes, possibly by altering cytokine signaling in the brain.

Stereotaxic localization of corticosterone to the amygdala enhances hypothalamo-pituitary–adrenal responses to behavioral stress

The amygdala is involved in behavioral, autonomic, and neuroendocrine responses to stressful stimuli. The goal of the current study was to determine the effect of directly elevating glucocorticoids in the amygdala on hypothalamo-pituitary–adrenocortical (HPA) responses to the elevated plus maze, a behavioral stressor known to activate the amygdala. Micropellets (30 μg) of crystalline corticosterone or cholesterol (control) were implanted bilaterally at the dorsal margin of the CeA in male Wistar rats; vascular catheters were also placed at this time. Five days post-surgery, blood samples were drawn at 07:00 and 19:00 h to assess diurnal rhythm of plasma corticosterone. At 7 days post-implantation, rats were subjected to behavioral stress using an elevated plus maze and blood was collected 15 min prior to stress, and at 15, 45, and 90 min after the initiation of the stressor. Corticotropin releasing factor (CRF) and arginine vasopressin (AVP) mRNA levels were analyzed by in situ hybridization in the medial parvocellular division of the hypothalamic paraventricular nucleus (mpPVN) in corticosterone- and cholesterol-implanted rats either not exposed to the elevated plus maze (control) or 4 h post-behavioral stress. Localization of corticosterone to the amygdala had no effect on diurnal rhythm of corticosterone secretion. Behavioral stress significantly increased peak plasma corticosterone levels in both groups to a similar level. However, in the corticosterone implanted rats, plasma corticosterone concentrations at 45 and 90 min post-stress were significantly greater compared to control rats indicating a prolonged corticosterone response to behavioral stress. In non-stressed rats, corticosterone delivery to the amygdala elevated basal CRF mRNA in the mpPVN to levels similar to those observed post-stress in control animals; no further increase was observed in CRF mRNA following stress. Behavioral stress resulted in a significant elevation in CRF mRNA in cholesterol controls. Basal AVP mRNA levels were unaffected by corticosterone implants. AVP mRNA did not increase in cholesterol implanted rats in response to behavioral stress. However, AVP mRNA levels were higher in corticosterone implanted rats post stress compared to cholesterol treated controls. In conclusion, direct administration of corticosterone to the amygdala increases plasma corticosterone in response to a behavioral stressor without altering the diurnal rhythm in plasma corticosterone. Elevated basal levels of mpPVN CRF mRNA, and the induction of a mpPVN AVP mRNA response to the behavioral stressor implicate enhanced ACTH secretagogue expression in the increased HPA response to corticosterone modulation of amygdala function.

Intracerebroventricular corticotropin-releasing factor increases limbic glucose metabolism and has social context-dependent behavioral effects in nonhuman primates.

Corticotropin-releasing factor (CRF) is a neuropeptide involved in integrating the behavioral, autonomic, and hormonal responses to stress within the central nervous system. Patients suffering from depression have abnormal activity in stress responsive brain regions and elevated cerebrospinal fluid CRF. The DSM-IV criteria for major depressive disorder include behavioral changes such as depressed mood, anhedonia, and psychomotor agitation/retardation. We studied the effects of 434 microgram of CRF given intracerebroventricularly over 40 min in group and individually housed monkeys to examine the role of elevated levels of central CRF on behavior. CRF elicited a wide range of behaviors, which fell into three broad categories: anxiety-like, depressive-like, and externally oriented. Externally oriented behaviors decreased, and anxiety-like behaviors increased regardless of how the animals were housed. Interestingly, increased depressive-like behaviors were only observed when the animals were socially housed. In a separate experiment, we examined the effects of the same dose of CRF on the regional cerebral glucose metabolism of lightly anesthetized monkeys by using positron emission tomography and [(18)F]fluorodeoxyglucose. CRF infusion increased glucose metabolism in the pituitary/infundibulum, the amygdala, and hippocampus. These results indicate that increased central CRF tone affects primate behavior in a context-dependent manner, and that it activates limbic and stress-responsive regions. The fact that intracerebroventricular CRF increases depressive-like behavior in socially housed animals and increases activity in limbic brain regions may help explain the behavioral and metabolic alterations in humans with affective disorders, and this model could therefore have significant value in the development of novel antidepressant treatments.

Non-peptidic CRF1 receptor antagonists for the treatment of anxiety, depression and stress disorders.

Anxiety and depression are psychiatric disorders that constitute a major health concern worldwide, and new pharmacological approaches with the potential for improved efficacy and decreased side effect profiles relative to currently marketed drugs are desired. Since the identification of corticotropin releasing factor (CRF) by Vale and colleagues in 1981, an extensive research effort has solidified the importance of this 41 amino acid peptide in mediating the body's behavioral, endocrine, and autonomic responses to stress. The further identification of CRF receptor subtypes has provided compelling targets for novel pharmaceutical agents. The present review focuses on the potential of non-peptidic antagonists of the CRF(1) receptor subtype as a novel therapeutic approach for the treatment of anxiety and depression. The first section reviews preclinical and clinical evidence implicating CRF, in general, and CRF(1) receptors, in particular, in anxiety and depression. Clinical studies have demonstrated a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis and/or elevated CRF levels in depression and in some anxiety disorders. Preclinical data utlilizing correlational methods, genetic models, and exogenous CRF administration techniques in rodents and non-human primates supports a link between hyperactive CRF pathways and anxiogenic and depressive-like symptoms. Studies employing the use of receptor knockouts and selective, non-peptidic antagonists of the CRF(1) receptor have demonstrated anxiolytic and antidepressant effects under certain types of laboratory conditions. A Phase II, open-label, clinical trial in major depressive disorder has reported that a CRF(1) receptor antagonist was safe and effective in reducing symptoms of anxiety and depression. In the second section, a topological approach is used to describe the design strategies employed to produce potent, non-peptidic CRF(1) receptor antagonists. Two main topologies, featuring a center core, a top side-chain, and a pending aromatic ring, can be used to characterize the vast majority of currently known CRF(1) receptor antagonists. By exploiting some of these structural elements, pharmacological, physicochemical, and pharmacokinetic properties can be modulated and optimized. However, as a result of a relatively conservative iteration process during the structural optimization, the chemical space presently defined by the existing CRF(1) receptor antagonists still remains fairly narrow. Expanding these structural and topological boundaries, while optimizing the "drug-like" properties of the CRF(1) receptor antagonists, seems to be a common objective across pharmaceutical companies to maximize the chances for a clinical success in the near future.

Neonatal maternal separation reduces hippocampal mossy fiber density in adult Long Evans rats

Neonatal maternal separation of rat pups leads to a stable stress hyper-responsive phenotype characterized by increased basal levels of corticotropin releasing factor (CRF) mRNA in the hypothalamic and extra-hypothalamic nuclei, increased hypothalamic CRF release, and enhanced adrenocorticotrophin hormone (ACTH) and corticosterone (CORT) responses to psychological stressors. Stress and exposure to glucocorticoids either early in life or in adulthood have been associated with hippocampal atrophy and impairments in learning and memory. In this study, male Long Evans rat pups were exposed to daily 3-h (HMS180) or 15-min (HMS15) periods of maternal separation on postnatal days (PND) 2–14 or normal animal facility rearing. Maternal separation and subsequent reunion with the dam resulted in elevated plasma CORT levels versus HMS15 animals at PND7, a time when rat pups are normally hyporesponsive to stressors and show limited pituitary–adrenal responses. As adults, HMS180 rats exhibited elevated indices of anxiety, startle-induced pituitary–adrenal hyper-responsiveness, and slight, but significant impairment on acquisition in the Morris water maze task. In addition, HMS180 rats exhibited decreased mossy fiber density in the stratum oriens region of the hippocampus as measured by Timm’s staining, but no change in volume of the dentate gyrus. These changes may be the result of neonatal exposure to elevated glucocorticoids and/or changes in other signaling systems in response to maternal separation. Overall the results suggest that repeated, daily, 3-h maternal separations during critical periods of hippocampal development can disrupt hippocampal cytoarchitecture in a stable manner. The resulting change in morphology may contribute to the subtle, but consistent learning deficit and overall stress hyper-responsive phenotype observed in these animals.

Levels of maternal plasma corticotropin-releasing factor and urocortin during labor

Corticotropin-releasing factor (CRF) is produced by the placenta and intrauterine tissues and secreted in increasing amounts from early to term pregnancy. In the presence of labor, a more incisive increase in CRF levels has been described, and women with preterm labor or those destined to have premature delivery have higher midpregnancy CRF levels than those who deliver at term. Urocortin is a 40-amino acid peptide belonging to the CRF family, expressed by human trophoblast and fetal membranes, which has the same biologic effects as CRF. Acting on the same CRF receptors, urocortin stimulates myometrial contractility and ACTH and prostaglandin release from cultured human placental cells. Because no data exist about urocortin levels in the maternal circulation at parturition, we investigated whether maternal plasma urocortin and CRF levels change according to cervical dilatation in healthy pregnant women at term labor. In a cross-sectional study of labor, a single maternal blood sample was collected from healthy pregnant women at term (n = 40); in a second longitudinal study, plasma samples were collected longitudinally in a subset of patients (n = 8) throughout labor, according to a Bishop score evaluation. Both maternal plasma CRF and urocortin levels were higher in labor than those previously reported during pregnancy, but they did not change significantly during the different stages of labor when evaluated longitudinally. Some patients showed a trend toward increasing levels, whereas others had variable concentrations. Neither CRF nor urocortin levels changed during the progression of spontaneous labor.

The Role of Corticotropin-Releasing Factor Receptors in Stress and Anxiety

Corticotropin releasing factor (CRF) is a critical integrator of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress. CRF and its related molecule urocortin (UCN) bind CRF receptor 1 (CRFR1) and CRFR2 with distinct affinities. Mice deficient for CRFR1 or CRFR2 were generated in order to determine the physiological role of these receptors. While CRFR1-mutant mice show a depleted stress response and display anxiolytic-like behavior, CRFR2-mutant mice are hypersensitive to stress and display anxiogenic-like behavior. Both CRFR1- and CRFR2-mutant mice show normal basal feeding and weight gain, but CRFR2-mutant mice exhibit decreased food intake following a stress of food deprivation. While CRFR2-mutant mice display increased levels of CRF mRNA in the central nucleus of the amygdala (cAmyg) but not in the paraventricular nucleus of the hypothalamus (PVN), the CRFR1-mutant mice express high levels of CRF in the PVN but normal levels in the cAmyg. CRFR2-mutant mice also display increased levels of Ucn mRNA and protein in the edinger westphal nucleus (EW) as well as an increased number of cells expressing Ucn. The levels of these CRF-receptor ligands reflect the state of the receptor-deficient mice. These results demonstrate a possible modulatory function of CRFR2 in response to CRFR1 stimulation of the HPA axis or anxiety.