Hypothalamic-pituitary-adrenocortical system and mood disorders: highlights from mutant mice

CRF-R1 Antagonist Treatment Exacerbates Circadian Corticosterone Secretion under Chronic Stress, but Preserves HPA Feedback Sensitivity

Despite promising initial reports, corticotropin-releasing factor receptor type-1 (CRF-R1) antagonists have mostly failed to display efficacy in clinical trials for anxiety or depression. Rather than broad-spectrum antidepressant/anxiolytic-like drugs, they may represent an ‘antistress’ solution for single stressful situations or for patients with chronic stress conditions. However, the impact of prolonged CRF-R1 antagonist treatments on the hypothalamic–pituitary–adrenal (HPA) axis under chronic stress conditions remained to be characterized. Hence, our study investigated whether a chronic CRF-R1 antagonist (crinecerfont, formerly known as SSR125543, 20 mg·kg⁻¹·day⁻¹ ip, 5 weeks) would alter HPA axis basal circadian activity and negative feedback sensitivity in mice exposed to either control or chronic stress conditions (unpredictable chronic mild stress, UCMS, 7 weeks), through measures of fecal corticosterone metabolites, plasma corticosterone, and dexamethasone suppression test. Despite preserving HPA axis parameters in control non-stressed mice, the 5-week crinercerfont treatment improved the negative feedback sensitivity in chronically stressed mice, but paradoxically exacerbated their basal corticosterone secretion nearly all along the circadian cycle. The capacity of chronic CRF-R1 antagonists to improve the HPA negative feedback in UCMS argues in favor of a potential therapeutic benefit against stress-related conditions. However, the treatment-related overactivation of HPA circadian activity in UCMS raise questions about possible physiological outcomes with long-standing treatments under ongoing chronic stress.

Endogenous opioids: opposing stress with a cost

The stress response is characterized by the coordinated engagement of central and peripheral neural systems in response to life-threatening challenges. It has been conserved through evolution and is essential for survival. However, the frequent or continual elicitation of the stress response by repeated or chronic stress, respectively, results in the dysfunction of stress response circuits, ultimately leading to stress-related pathology. In an effort to best respond to stressors, yet at the same time maintain homeostasis and avoid dysfunction, stress response systems are finely balanced and co-regulated by neuromodulators that exert opposing effects. These opposing systems serve to restrain certain stress response systems and promote recovery. However, the engagement of opposing systems comes with the cost of alternate dysfunctions. This review describes, as an example of this dynamic, how endogenous opioids function to oppose the effects of the major stress neuromediator, corticotropin-releasing hormone, and promote recovery from a stress response and how these actions can both protect and be hazardous to health.

Role of mecp2 in experience-dependent epigenetic programming

Mutations in the X-linked gene MECP2, the founding member of a family of proteins recognizing and binding to methylated DNA, are the genetic cause of a devastating neurodevelopmental disorder in humans, called Rett syndrome. Available evidence suggests that MECP2 protein has a critical role in activity-dependent neuronal plasticity and transcription during brain development. Moreover, recent studies in mice show that various posttranslational modifications, notably phosphorylation, regulate Mecp2’s functions in learning and memory, drug addiction, depression-like behavior, and the response to antidepressant treatment. The hypothalamic-pituitary-adrenal (HPA) axis drives the stress response and its deregulation increases the risk for a variety of mental disorders. Early-life stress (ELS) typically results in sustained HPA-axis deregulation and is a major risk factor for stress related diseases, in particular major depression. Interestingly, Mecp2 protein has been shown to contribute to ELS-dependent epigenetic programming of Crh, Avp, and Pomc, all of these genes enhance HPA-axis activity. Hereby ELS regulates Mecp2 phosphorylation, DNA binding, and transcriptional activities in a tissue-specific and temporospatial manner. Overall, these findings suggest MECP2 proteins are so far underestimated and have a more dynamic role in the mediation of the gene-environment dialog and epigenetic programming of the neuroendocrine stress system in health and disease.

Endogenous Opioids: The Downside of Opposing Stress

Our dynamic environment regularly exposes us to potentially life-threatening challenges or stressors. To answer these challenges and maintain homeostasis, the stress response, an innate coordinated engagement of central and peripheral neural systems is initiated. Although essential for survival, the inappropriate initiation of the stress response or its continuation after the stressor is terminated has pathological consequences that have been linked to diverse neuropsychiatric and medical diseases. Substantial individual variability exists in the pathological consequences of stressors. A theme of this Special Issue is that elucidating the basis of individual differences in resilience or its flipside, vulnerability, will greatly advance our ability to prevent and treat stress-related diseases. This can be approached by studying individual differences in "pro-stress" mediators such as corticosteroids or the hypothalamic orchestrator of the stress response, corticotropin-releasing factor. More recently, the recognition of endogenous neuromodulators with "anti-stress" activity that have opposing actions or that restrain stress-response systems suggests additional bases for individual differences in stress pathology. These "anti-stress" neuromodulators offer alternative strategies for manipulating the stress response and its pathological consequences. This review uses the major brain norepinephrine system as a model stress-response system to demonstrate how co-regulation by opposing pro-stress (corticotropin-releasing factor) and anti-stress (enkephalin) neuromodulators must be fine-tuned to produce an adaptive response to stress. The clinical consequences of tipping this fine-tuned balance in the direction of either the pro- or anti-stress systems are emphasized. Finally, that each system provides multiple points at which individual differences could confer stress vulnerability or resilience is discussed.

Unraveling the mechanisms responsible for the comorbidity between metabolic syndrome and mental health disorders

The increased prevalence and high comorbidity of metabolic syndrome (MetS) and mental health disorders (MHDs) have prompted investigation into the potential contributing mechanisms. There is a bidirectional association between MetS and MHDs including schizophrenia, bipolar disorder, depression, anxiety, attention-deficit/hyperactivity disorder, and autism spectrum disorders. Medication side effects and social repercussions are contributing environmental factors, but there are a number of shared underlying neurological and physiological mechanisms that explain the high comorbidity between these two disorders. Inflammation is a state shared by both disorders, and it contributes to disruptions of neuroregulatory systems (including the serotonergic, dopaminergic, and neuropeptide Y systems) as well as dysregulation of the hypothalamic-pituitary-adrenal axis. MetS in pregnant women also exposes the developing fetal brain to inflammatory factors that predispose the offspring to MetS and psychopathologies. Due to the shared nature of these conditions, treatment should address aspects of both mental health and metabolic disorders. Additionally, interventions that can interrupt the transfer of increased risk of the disorders to the next generation need to be developed. © 2013 S. Karger AG, Basel.

The molecular physiology of CRH neurons

Corticotropin releasing hormone (CRH) is essential for stress adaptation by mediating hypothalamic-pituitary-adrenal (HPA) axis, behavioral and autonomic responses to stress. Activation of CRH neurons depends on neural afferents from the brain stem and limbic system, leading to sequential CRH release and synthesis. CRH transcription is required to restore mRNA and peptide levels, but termination of the response is essential to prevent pathology associated with chronic elevations of CRH and HPA axis activity. Inhibitory feedback mediated by glucocorticoids and intracellular production of the repressor, Inducible Cyclic AMP Early Repressor (ICER), limit the magnitude and duration of CRH neuronal activation. Induction of CRH transcription is mediated by the cyclic AMP/protein kinase A/cyclic AMP responsive element binding protein (CREB)-dependent pathways, and requires cyclic AMP-dependent nuclear translocation of the CREB co-activator, Transducer of Regulated CREB activity (TORC). This article reviews current knowledge on the mechanisms regulating CRH neuron activity.

Dysfunction of the hypothalamic-pituitary-adrenal axis in STX1A knockout mice

HPC-1/syntaxin1A (STX1A) is considered to regulate exocytosis in neurones and endocrine cells. Previously, we reported that STX1A null mutant (STX1A KO) mice unexpectedly showed normal glutamatergic and GABAergic fast synaptic transmission but exhibited disturbances in monoaminergic transmission, such as serotonin, 5-hydroxytryptamine (5-HT), which may induce attenuation of latent inhibition. These results suggest that STX1A may contribute to dense-core vesicle exocytosis in vivo. Thus, we hypothesised that the lack of STX1A might affect the secretion of several hormones, as also mediated by dense-core vesicles exocytosis. In the present study, we focused on the hypothalamic-pituitary-adrenal (HPA) axis, which is a neuroendocrine system that regulates responses to stress stimuli and is considered to be associated with neuropsychiatric disorders. Specifically, we examined whether the HPA axis is impaired in STX1A KO mice. Interestingly, plasma concentrations of both corticosterone (CORT) and adrenocorticotrophin hormone (ACTH) during the resting condition decreased in STX1A KO mice compared to WT mice. Additionally, elevated plasma CORT, ACTH and corticotrophin-releasing hormone (CRH) which were usually observed after acute restraint stress, were also reduced in STX1A KO mice. We also observed the suppression of 5-HT-induced CRH release in STX1A KO mice in vitro. Furthermore, an in vivo microdialysis study revealed that the elevation of extracellular 5-HT in the hypothalamus, which was induced by the selective serotonin reuptake inhibitor, fluoxetine, was significantly reduced in STX1A KO mice compared to WT mice. 5-HT elevation in the hypothalamus, which was induced by acute restraint stress, was also reduced in STX1A KO mice. Finally, STX1A KO mice showed abnormal behavioural responses after mild restraint stress. These results indicate that the lack of STX1A could induce dysfunction of the HPA axis, and the deficit may result in abnormal behavioural properties, such as unusual responses to stress stimuli.

Cardiac arrest and cardiopulmonary resuscitation dysregulates the hypothalamic-pituitary-adrenal axis

Cardiac arrest and cardiopulmonary resuscitation (CA/CPR) increase the risk for affective disorders in human survivors. Postischemic anxiety- and depressive-like behaviors have been documented in animal models of CA/CPR; however, the stability of post-CA/CPR anxiety-like behavior over time and the underlying physiologic mechanisms remain unknown. The hypothalamic-pituitary-adrenal (HPA) axis and the corticotropin releasing factor (CRF) system may mediate the pathophysiology of anxiety and depression; therefore, this study measured CA/CPR-induced changes in CRF receptor binding and HPA axis negative feedback. Mice were exposed to CA/CPR or SHAM surgery and assessed 7 or 21 days later. Consistent with earlier demonstrations of anxiety-like behavior 7 days after CA/CPR, increased anxiety-like behavior in the open field was also present 21 days after CA/CPR. On postoperative day 7, CA/CPR was associated with an increase in basal serum corticosterone concentration relative to SHAM, but this difference resolved by postoperative day 21. The Dexamethasone Suppression Test showed that the CA/CPR group had enhanced negative feedback compared with SHAM controls at postoperative day 21. Furthermore, there was a gradual increase in CRF(1) receptor binding in the paraventricular nucleus of the hypothalamus and bed nucleus of the stria terminalis, as well as a transient decrease of both CRF(1) and CRF(2A) receptors in the dorsal hippocampus. Therefore, sustained changes in activity of the HPA axis and the CRF system after CA/CPR may contribute to the postischemic increase in affective disorders.

TRH and TRH-like peptide expression in rat following episodic or continuous corticosterone

Sustained abnormalities of glucocorticoid levels have been associated with neuropsychiatric illnesses such as major depression, posttraumatic stress disorder (PTSD), panic disorder, and obsessive compulsive disorder. The pathophysiological effects of glucocorticoids may depend not only on the amount of glucocorticoid exposure but also on its temporal pattern, since it is well established that hormone receptors are down-regulated by continuously elevated cognate hormones. We have previously reported that TRH (pGlu-His-Pro-NH2) and TRH-like peptides (pGlu-X-Pro-NH2) have endogenous antidepressant-like properties and mediate or modulate the acute effects of a single i.p. injection of high dose corticosterone (CORT) in rats. For these reasons, two accepted methods for inducing chronic hyperglucocorticoidemia have been compared for their effects on brain and peripheral tissue levels of TRH and TRH-like peptides in male, 250 g, Sprague-Dawley rats: (1) the dosing effect of CORT hemisuccinate in drinking water, and (2) s.c. slow-release pellets. Overall, there were 93% more significant changes in TRH and TRH-like peptide levels in brain and 111% more in peripheral tissues of those rats ingesting various doses of CORT in drinking water compared to those with 1-3 s.c. pellets. We conclude that providing rats with CORT in drinking water is a convenient model for the pathophysiological effects of hyperglucocorticoidemia in rodents.

Neuroendocrine pathways in benzodiazepine dependence: new targets for research and therapy

Benzodiazepines are known to modulate the activity of the hypothalamo-pituitary-adrenocortical (HPA) axis by antagonizing the effects of corticotropin-releasing factor (CRH). Besides regulating the HPA axis CRH evolves properties of a neurotransmitter in the limbic system that is closely involved in the delivery of the emotional consequences of the stress response. At a superordinated level Neuropeptide Y (NPY) and Cholecystokinin (CCK) affect the release of CRH and modulate thereby the intensity of the physiological stress response. Benzodiazepine treatment interferes not only with the release of CRH but also with the release of NPY and CCK. Alterations in the intracortical ratio of NPY, CCK and CRH are correlated with behavioural changes like increased respectively decreased anxiety and subsequent alterations in the activity of the HPA axis. Recent research offers the possibility that the alterations of plasma levels of these neuropeptides are not only a secondary phenomenon due to drug intake, but that low levels of those neuropeptides that modulate anxiety and fear can possibly explain addiction to substances that counterbalance these deficits. Depending on the available results possible implications of NPY and CCK on benzodiazepine addiction and withdrawal symptoms are reviewed, thereby providing topics for further research.

Localization of glucocorticoid-induced leucine zipper (GILZ) expressing neurons in the central nervous system and its relationship to the stress response

The glucocorticoid-induced leucine zipper (GILZ) is a 137 amino acid protein, which was originally identified as a dexamethasone-inducible gene, and is characterized by a leucine zipper domain, an N-terminal domain and a C-terminal proline and glutamic acid rich domain. In this study, we performed in situ hybridization analyses and found that many neurons from the olfactory bulb to the spinal cord express GILZ mRNA, suggesting that GILZ is involved in fundamental and common cellular events of neurons. In addition, the predominant expression of GILZ mRNA in the motor nuclei indicated a strong relationship between GILZ and the motor nervous system. On the other hand, real-time RT-PCR analyses of brains of animals exposed to water-immersion restraint stress (WRS) showed that WRS significantly up-regulated GILZ expression in the medial prefrontal cortex (mPFC) and hippocampus, which are known to be mental stress-related areas, suggesting the multiple roles of GILZ in the brain. This up-regulation was not observed in adrenalectomized mice, confirming its dependency on hypothalamic-pituitary-adrenal axis activation.

Conditional gene targeting in the mouse nervous system: Insights into brain function and diseases

Conditional gene knockout represents an extremely powerful approach to study the function of single genes in the nervous system. The Cre-LoxP system is the most advanced technology for spatial and temporal control of genetic inactivation, and there is rapid progress using this methodology in neuroscience research. In this approach, mice with LoxP sites flanking the gene of interest (floxed mice) are bred with transgenic mice expressing Cre recombinase under the control of a selected promoter (Cre mice). This promoter is critical in that it determines the time and site of Cre expression. Cre enzyme, in turn, recombines the floxed gene and produces gene knockout. Here we review Cre mouse lines that have been developed to target either the entire brain, selected brain areas, or specific neuronal populations. We then summarize phenotypic consequences of conditional gene targeting in the brain for more than 40 genes, as reported to date. For many broadly expressed genes, brain-restricted knockout has overcome lethality of conventional knockout (KO) and has highlighted a specific role of the encoded protein in some aspect of brain function. In the case of neural genes, data from null mutants in specific brain sites or neurons has refined our understanding of the role of individual molecules that regulate complex behaviors or synaptic plasticity within neural circuits. Among the many developing functional genomic approaches, conditional gene targeting in the mouse has become an excellent tool to elucidate the function of the approximately 5000 known or unknown genes that operate in the nervous system.

Glucocorticoids: exemplars of multi-tasking

Well over 80 years ago Philip Smith described the beneficial clinical effects of adrenocortical extracts in animal models of adrenal insufficiency. In the ensuing years, scientists across the globe have sought to understand the mechanisms by which adrenal hormones and their synthetic analogues produce their complex and varied actions. Particular attention has focused on the glucocorticoids, partly because they have a vital place in the treatment of inflammatory and autoimmune disorders but also because dysregulation of the secretion and/or activity of endogenous glucocorticoids is increasingly implicated in a number of common disorders that pose a growing clinical burden, such as obesity, type II diabetes, the metabolic syndrome, hypertension and depression. This review considers some of the key advances that have been made in our understanding of the physiology, pathology and pharmacology of the glucocorticoids. Emphasis is placed on the molecular mechanisms of glucocorticoid signalling and the complex mechanisms that regulate the access of steroids in the systemic circulation to their receptors in their various target cells and tissues. In addition, consideration is given to the irreversible 'organisational' actions of glucocorticoids in perinatal life and to the potential role of the steroids in the aetiology of disease.

Prediction of treatment response by HPA-axis and glucocorticoid receptor polymorphisms in major depression

OBJECTIVE

We investigated whether treatment response is predicted by hypothalamus-pituitary-adrenal (HPA) axis parameters, or by genetic polymorphisms in the glucocorticoid receptor (GR), that regulates its feedback.

METHODS

Ninety-eight outpatients completed 8 weeks of paroxetine treatment. Treatment response was defined as a 50% decrease in Hamilton Rating Scale for depression (HRSD) ratings. At baseline, 24h urinary cortisol excretion, and cortisol and ACTH concentrations in a DEX/CRH test were measured. The presence of polymorphisms in the GR DNA sequence (BclI, ER22/23EK, N363S) was determined. Prediction of treatment response was analysed by calculating response rates per tertile of an HPA-axis parameter and per GR genotype.

RESULTS

The response rate in the high ACTH tertile was significantly lower as compared to the intermediate tertile, but not compared to the low tertile (response rates from high to low tertile: 33%, 67% and 42%). Carriers of the BclI polymorphism had higher ACTH values than non-carriers (baseline ACTH: 3 versus 5ng/l, p=0.02) and showed a trend towards lower decrease of HRSD rates than non-carriers (HRSD decrease: 8 versus 11, respectively, p=0.07). In a subgroup of BclI carriers, patients in the high ACTH tertile had a lower decrease in HRSD and lower response rates than patients in the low ACTH tertiles (HRSD decrease from high to low tertile: 5, 9 and 11, p<0.01).

CONCLUSION

The results suggest that hyperactivity of the HPA-axis predict worse treatment outcome. The BclI polymorphism explains, in part, DEX/CRH test results and tends to be associated with worse treatment outcome.

Approaching the shared biology of obesity and depression: the stress axis as the locus of gene-environment interactions

Obesity and depression are serious public health problems and also constitute cardiovascular disease risk factors. Research organizations have called for efforts to explore the interrelationship between obesity and depression. A useful starting point is the fact that in both disorders there is dysregulation of stress systems. We review molecular and clinical evidence indicating that the mediators of the stress response are a key locus for gene-environment interactions in the shared biology of depression and obesity. Scientific milestones include translational paradigms such as mice knockouts, imaging and pharmacogenomic approaches that can identify new therapeutic strategies for those burdened by these two afflictions of contemporary civilization. Perspectives for the future are promising. Our ability to dissect the underpinnings of common and complex diseases with shared substrates will be greatly enhanced by the Genes and Environment Initiative, the emerging Large Scale Studies of Genes and Environment in Common Disease, and the UK Biobank Project.

Role of drug efflux transporters in the brain for drug disposition and treatment of brain diseases

The blood-brain barrier (BBB) serves as a protective mechanism for the brain by preventing entry of potentially harmful substances from free access to the central nervous system (CNS). Tight junctions present between the brain microvessel endothelial cells form a diffusion barrier, which selectively excludes most blood-borne substances from entering the brain. Astrocytic end-feet tightly ensheath the vessel wall and appear to be critical for the induction and maintenance of the barrier properties of the brain capillary endothelial cells. Because of these properties, the BBB only allows entry of lipophilic compounds with low molecular weights by passive diffusion. However, many lipophilic drugs show negligible brain uptake. They are substrates for drug efflux transporters such as P-glycoprotein (Pgp), multidrug resistance proteins (MRPs) or organic anion transporting polypeptides (OATPs) that are expressed at brain capillary endothelial cells and/or astrocytic end-feet and are key elements of the molecular machinery that confers the special permeability properties to the BBB. The combined action of these carrier systems results in rapid efflux of xenobiotics from the CNS. The objective of this review is to summarize transporter characteristics (cellular localization, specificity, regulation, and potential inhibition) for drug efflux transport systems identified in the BBB and blood-cerebrospinal fluid (CSF) barrier. A variety of experimental approaches available to ascertain or predict the impact of efflux transport on brain access of therapeutic drugs also are described and critically discussed. The potential impact of efflux transport on the pharmacodynamics of agents acting in the CNS is illustrated. Furthermore, the current knowledge about drug efflux transporters as a major determinant of multidrug resistance of brain diseases such as epilepsy is reviewed. Finally, we summarize strategies for modulating or by-passing drug efflux transporters at the BBB as novel therapeutic approaches to drug-resistant brain diseases.

Colocalization of corticotropin-releasing hormone and oestrogen receptor-alpha in the paraventricular nucleus of the hypothalamus in mood disorders

Oestrogens may modulate the activity of the hypothalamic-pituitary-adrenal (HPA) axis. The present study was to investigate whether the activity of the HPA axis in mood disorders might be directly modulated by oestrogens via oestrogen receptors (ORs) in the corticotropin-releasing hormone (CRH) neurons of the human hypothalamic paraventricular nucleus (PVN). Brains of 13 subjects ranging in age between 45 and 79 years suffering from major depression/major depressive disorder (eight cases) or bipolar disorder (five cases) and of 13 controls, matched for sex, age, brain weight, post-mortem delay, fixation time and season and clock time at death, were studied with double-label immunocytochemistry. The total number of CRH-immunoreactive (IR) neurons, CRH neurons that colocalized ORalpha in the neuronal nucleus and the number of only nuclear ORalpha-containing neurons in the PVN were measured using an image analysis system. In addition, the volume of the PVN delineated on the basis of CRH neurons was determined. It was found that the total number of CRH-IR neurons in patients with mood disorders was nearly 1.7 times higher than in controls (P = 0.034). A novel finding was that the total number of CRH-IR neurons and the number of CRH-nuclear ORalpha double-staining neurons in the PVN were strongly correlated both in controls and in patients with mood disorders (P < 0.001 and P = 0.022, respectively). The ratio of the CRH-nuclear-ORalpha double-staining neurons to the total CRH-IR neurons in patients with mood disorders was similar to that in the controls (P = 0.448). The volume of the sub-region of the PVN that was delineated on the basis of CRH neurons was significantly larger in patients with mood disorders than in controls (P = 0.022). Another novel finding was the large population of extra-hypothalamic CRH neurons that was found in the thalamus. In summary, oestrogens may directly influence CRH neurons in the human PVN. The increased numbers of neurons expressing CRH in mood disorders is accompanied by increased ORalpha colocalization in the nucleus of these neurons. These changes seem to be trait- rather than state-related.

Effects of chronic social stress on neuroendocrine responsiveness to challenge with ethanol, dexamethasone and corticotropin-releasing hormone

Neuroendocrine and behavioral profiles of group-housed rodents differ from those of singly-housed ones. Subordinate rats have elevated plasma corticosterone (CORT) concentration and impaired activity of the hypothalamic-pituitary-adrenal (HPA) axis compared to dominant cagemates. However, little is known about the effects of social hierarchy on other stress-related hormones. We examined plasma prolactin (PRL) and CORT responses to saline and ethanol (EtOH) injections, and 1 month later to dexamethasone (DEX) and corticotropin-releasing hormone (CRH) challenges of group- (triad) and single-housed male rats over a period of 225 days. Social status was determined from behaviors displayed upon initial triad housing. Subordinate rats had lower basal PRL and higher CORT compared to dominant rats. The injection of EtOH (1.25 g/kg) depressed PRL and elevated CORT levels significantly more than the saline injection only in dominant and singly-housed rats. DEX increased PRL levels, most strikingly in dominant rats, and suppressed CORT only in dominant rats. After CRH challenge, plasma CORT increased in all groups, subdominant and subordinate rats displaying blunted responses. Our data demonstrate that social rank and housing conditions affect plasma PRL and CORT concentrations, and modify responses to EtOH, possibly reflecting impairments of HPA axis regulation in socially-housed rats.

Nonpeptide corticotropin-releasing hormone receptor type 1 antagonists and their applications in psychosomatic disorders

Overproduction of corticotropin-releasing hormone (CRH) and stress system abnormalities are seen in psychiatric diseases such as depression, anxiety, eating disorders, and addiction. Investigations of CRH type 1 receptor (CRHR1) nonpeptide antagonists suggest therapeutic potential for treatment of these and other neuropsychiatric diseases. However, overproduction of CRH in the brain and on its periphery and disruption of the hypothalamic-pituitary-adrenal axis are also found in 'somatic' disorders. Some rare forms of Cushing's disease and related pituitary/adrenal disorders are obvious applications for CRHR1 antagonists. In addition, however, these antagonists may also be effective in treating more common somatic diseases. Patients with obesity and metabolic syndrome who often have subtle, but chronic hypothalamic-pituitary-adrenal hyperactivity, which may reflect central dysregulation of CRH and consequently glucocorticoid hypersecretion, could possibly be treated by administration of CRHR1 antagonists. Hormonal, autonomic, and immune aberrations are also present in chronic inflammatory, autoimmune, and allergic diseases, with considerable evidence linking CRH with the observed abnormalities. Furthermore, autonomic dysregulation is a prominent feature of common gastrointestinal disorders, such as irritable bowel syndrome and peptic ulcer disease. Patients with irritable bowel syndrome and other gastrointestinal disorders frequently develop altered pain perception and affective symptoms. CRH acts peripherally to modulate bowel activity both directly through the autonomic system and centrally by processing viscerosensory and visceromotor neural signals. This review presents clinical and preclinical evidence for the role of CRH in the pathophysiology of these disorders and for potential diagnostic and therapeutic applications of CRHR1 antagonists. Recognition of a dysfunctional stress system in these and other diseases will alter the understanding and treatment of 'psychosomatic' disorders.