BACKGROUND

Stressful events during periods of drug abstinence likely contribute to relapse in cocaine-dependent individuals. Excessive cocaine use may increase susceptibility to stressor-induced relapse through alterations in brain corticotropin-releasing factor (CRF) responsiveness.

OBJECTIVE

This study examined stressor- and CRF-induced cocaine seeking and other stress-related behaviors in rats with different histories of cocaine self-administration (SA).

METHODS

Rats self-administered cocaine under short-access (ShA; 2 h daily) or long-access (LgA; 6 h daily) conditions for 14 days or were provided access to saline and were tested for reinstatement by a stressor (electric footshock), cocaine or an icv injection of CRF and for behavioral responsiveness on the elevated plus maze, in a novel environment and in the light-dark box after a 14- to 17-day extinction/withdrawal period.

RESULTS

LgA rats showed escalating patterns of cocaine SA and were more susceptible to reinstatement by cocaine, EFS, or icv CRF than ShA rats. Overall, cocaine SA increased activity in the center field of a novel environment, on the open arms of the elevated plus maze, and in the light compartment of a light-dark box. In most cases, the effects of cocaine SA were dependent on the pattern/amount of cocaine intake with statistically significant differences from saline self-administering controls only observed in LgA rats.

CONCLUSIONS

When examined after several weeks of extinction/withdrawal, cocaine SA promotes a more active pattern of behavior during times of stress that is associated with a heightened susceptibility to stressor-induced cocaine-seeking behavior and may be the consequence of augmented CRF regulation of addiction-related neurocircuitry.

Anxiety disorders are a highly prevalent and disabling class of psychiatric disorders. This review focuses on new directions in neurobiological research and implications for the development of novel psychopharmacological treatments. Neuroanatomical and neuroimaging research in anxiety disorders has centered on the role of the amygdala, reciprocal connections between the amygdala and the prefrontal cortex, and, most recently, alterations in interoceptive processing by the anterior insula. Anxiety disorders are characterized by alterations in a diverse range of neurochemical systems, suggesting ample novel targets for drug therapies. Corticotropin-releasing factor (CRF) concentrations are elevated in a subset of anxiety disorders, which suggests the potential utility of CRF receptor antagonists. Pharmacological blockade of the memory-enhancing effects of stress hormones such as glucocorticoids and noradrenaline holds promise as a preventative approach for trauma-related anxiety. The glutamatergic system has been largely overlooked as a potential pharmacological target, although convergent preclinical, neuroimaging, and early clinical findings suggest that glutamate receptor antagonists may have potent anxiolytic effects. Glutamatergic receptor agonists (e.g., D-cycloserine) also have an emerging role in the treatment of anxiety as facilitators of fear extinction during concurrent behavioral interventions. The neuropeptides substance P, neuropeptide Y, oxytocin, orexin, and galanin are each implicated in anxiety pathways, and neuropeptide analogs or antagonists show early promise as anxiolytics in preclinical and/or clinical research. Each of these active areas of research holds promise for expanding and improving evidence-based treatment options for individuals suffering with clinical anxiety.

The recent identification and differential localization in brain of three binding sites for corticotropin-releasing factor (CRF)-like peptides (CRF1 and CRF2 receptors as well as CRF-binding protein) suggest the existence of functionally distinct neurobiological systems which mediate CRF activation. For instance, evidence from receptor knockdown and pharmacological studies suggest involvement of the CRF1 receptor in anxiogenic-like behavior and the CRF-binding protein in learning and memory processes. The present studies examined the potential functional significance of the CRF2 receptor in relation to the CRF1 receptor using two animal models of anxiety and endocrine reactivity to a stressor. CRF1 and CRF2 receptor knockdown was achieved and confirmed autoradiographically within brain regions relevant to behavioral reactivity to stressors by chronic, central administration of antisense oligonucleotides. CRF1 but not CRF2, know down produced a significant anxiolytic-like effect in the Defensive Withdrawal relative to vehicle-treated and two missense oligonucleotide negative control groups. In contrast, neither antisense treatment altered endocrine or behavioral reactivity to a swim stressor. Thus, the present data support the reported role of CRF1 receptors in the mediation of anxiogenic-like behavior and suggest a functionally distinct for role for CRF2 receptors in brain.

Corticotropin-releasing factor (CRF) has been hypothesized to be involved in the pathophysiology of anxiety, depression, cognitive and feeding disorders. Two distinct CRF receptor subtypes, CRFR1 and CRFR2, are thought to mediate CRF actions in the CNS. However, the role for each receptor subtype in animal models of neuropsychiatric disorders remains to be determined. Using CRFR1 deficient mice, the present study investigated the functional significance of this CRF receptor subtype in anxiety-like and memory processes. CRFR1 knockout mice displayed an increased exploratory behavior in both the Elevated Plus-maze (EPM) and the Black and White (B-W) test box models of anxiety, indicating an anxiolytic-like effect of the CRFR1 gene deletion. In contrast, during the retrieval trial of a two-trial spatial memory task wild type mice made more visits to and spent more time in the novel arm as opposed to the two familiar ones of a Y-maze apparatus. No increase in the level of exploration of the novel arm by the CRFR1 deficient mice was observed. This indicates that CRFR1 knockout mice are impaired in spatial recognition memory. These results demonstrate that genetic deletion of the CRFR1 receptor can lead to impairments in anxiety-like and cognitive behaviors, supporting a critical role for this receptor in anxiety and cognitive biological processes.

CRH is synthesized in the hypothalamus and released in response to stress into the portal hypophyseal blood; an additional site of synthesis, the placenta, is present only during pregnancy. Placental CRH is released into the maternal and fetal circulation during human pregnancy, and we hypothesized that the chronic fetal stress associated with fetal growth retardation may stimulate placental CRH release. We measured plasma CRH concentrations in the umbilical cord blood of 28 growth-retarded fetuses and 28 normally grown fetuses matched for gestational age and mode of delivery. Plasma ACTH, dehydroepiandrosterone sulfate (DHEAS), and cortisol were also measured in the umbilical cord samples to determine if CRH levels were correlated with levels of pituitary and adrenal hormones. The mean umbilical cord plasma CRH level in the growth-retarded fetuses was 206 +/- 25.8 pmol/L, which was significantly higher than that in the normally grown fetuses matched for gestational age, presence or absence of labor, and mode of delivery (49.4 +/- 16.7 pmol/L; P < 0.01). The mean plasma ACTH level in the growth-retarded fetuses (5.7 +/- 1.2 pmol/L) was significantly higher than that in the normally grown fetuses (3.3 +/- 0.7 pmol/L; P < 0.05). The mean cortisol concentration in the growth-retarded fetuses was 260 +/- 32.5 nmol/L, and that in the normally grown fetuses was 220 +/- 40 nmol/L. The mean DHEAS level was significantly lower in the growth-retarded fetuses (4.8 +/- 0.6 mumol/L) than that in the normally grown fetuses (7.7 +/- 0.6 mumol/L; P < 0.001). There was a significant correlation between umbilical cord plasma CRH and both ACTH and cortisol concentrations as well as a significant negative correlation between CRH and DHEAS levels in the growth-retarded fetuses. The umbilical cord plasma CRH level is extremely elevated in growth-retarded fetuses compared to that in normal fetuses. Placental CRH, like hypothalamic CRH, may be stimulated in conditions of chronic stress and may modulate fetal pituitary-adrenal function in high risk pregnancies.

BACKGROUND

Use of etomidate in the critically ill is controversial due to its links with an inadequate response to corticotropin and potential for excess mortality. In a septic shock population, we tested the hypotheses that etomidate administration induces more non-responders to corticotropin and increases mortality and that hydrocortisone treatment decreases mortality in patients receiving etomidate.

METHODS

An a-priori sub-study of the CORTICUS multi-centre, randomised, double-blind, placebo-controlled trial of hydrocortisone in septic shock. Use and timing of etomidate administration were collected. Endpoints were corticotropin response and all-cause 28-day mortality in patients receiving etomidate.

RESULTS

Five hundred patients were recruited, of whom 499 were analysable; 96 (19.2%) were administered etomidate within the 72 h prior to inclusion. The proportion of non-responders to corticotropin was significantly higher in patients who were given etomidate in the 72 h before trial inclusion than in other patients (61.0 vs. 44.6%, P = 0.004). Etomidate therapy was associated with a higher 28-day mortality in univariate analysis (P = 0.02) and after correction for severity of illness (42.7 vs. 30.5%; P = 0.06 and P = 0.03) in our two multi-variant models. Hydrocortisone administration did not change the mortality of patients receiving etomidate (45 vs. 40%).

CONCLUSIONS

The use of bolus dose etomidate in the 72 h before study inclusion is associated with an increased incidence of inadequate response to corticotropin, but is also likely to be associated with an increase in mortality. We recommend clinicians demonstrate extreme caution in the use of etomidate in critically ill patients with septic shock.

Relative adrenal insufficiency is frequent in patients with severe sepsis and is associated with hemodynamic instability, renal failure, and increased mortality. This study prospectively evaluated the effects of steroids on shock resolution and hospital survival in a series of 25 consecutive patients with cirrhosis and septic shock (group 1). Adrenal function was evaluated by the short corticotropin test within the first 24 hours of admission. Patients with adrenal insufficiency were treated with stress doses of intravenous hydrocortisone (50 mg/6 h). Data were compared to those obtained from the last 50 consecutive patients with cirrhosis and septic shock admitted to the same intensive care unit in whom adrenal function was not investigated and who did not receive treatment with steroids (group 2). Incidence of adrenal insufficiency in group 1 was 68% (17 patients). Adrenal dysfunction was frequent in patients with advanced cirrhosis (Child C: 76% vs. Child B: 25%, P = .08). Resolution of septic shock (96% vs. 58%, P = .001), survival in the intensive care unit (68% vs. 38%, P = .03), and hospital survival (64% vs. 32%, P = .003) were significantly higher in group 1. The main causes of death in group 1 were hepatorenal syndrome or liver failure (7 of 9 patients). In contrast, refractory shock caused most of the deaths in group 2 (20 of 34 patients). In conclusion, relative adrenal insufficiency is very frequent in patients with advanced cirrhosis and septic shock. Hydrocortisone administration in these patients is associated with a high frequency of shock resolution and high survival rate.

BACKGROUND

Epidemiologic and clinical studies suggest comorbidity between major depressive disorder (MDD) and obesity. To elucidate the impact of weight on the course of depression beyond comorbidity, we investigated psychopathology, attention, neuroendocrinology, weight change, and treatment response in MDD patients, depending on their weight.

METHODS

Four hundred eight inpatients with MDD participated in the Munich Antidepressant Response Signature Study, designed to discover biomarkers and genotypes that are predictive for clinical outcome. Psychopathology and anthropometric parameters were monitored weekly in 230 patients. In subsamples, combined dexamethasone-corticotropin-releasing hormone and attention tests were conducted at admission and discharge. One thousand twenty-nine diagnosed matched controls served for morphometric comparisons.

RESULTS

Patients with MDD had a significantly higher body mass index (BMI) compared with healthy controls. Patients with high BMI >> or =25) showed a significantly slower clinical response, less improvement in neuroendocrinology and attention, and less weight gain than did patients with normal BMI (18.5 < or = BMI < 25) during antidepressant treatment.

CONCLUSIONS

Our findings suggest that overweight and obesity characterize a subgroup of MDD patients with unfavorable treatment outcome.

Urocortin (Ucn) III, or stresscopin, is a high affinity ligand for the type 2 corticotropin-releasing factor (CRFR2) receptor recently identified in rodents and human. Ucn III was initially identified as a neuropeptide expressed in discrete areas in the brain. In the present study, we demonstrate that Ucn III is expressed in pancreatic beta-cells and in a mouse beta-cell line, MIN6. Ucn III secretion from the cells was measured using a highly specific RIA, and we found that high potassium, forskolin, or high glucose can stimulate Ucn III secretion from these cells. In vivo studies showed that rats receiving an iv Ucn III injection had a significant elevation of plasma glucagon followed by plasma glucose levels compared with rats receiving vehicle. Ucn III injections also result in an increase in plasma insulin levels. The observed effects of Ucn III were blocked by pretreatment with a CRFR2 antagonist, astressin(2)-B. Furthermore, Ucn III stimulated glucagon and insulin release from isolated rat islets, and astressin(2)-B abolished the effects of Ucn III, in keeping with a CRFR2-mediated mechanism. Taken together, the present studies suggest pancreatic Ucn III acting through CRFR2 is involved in the local regulation of glucagon and insulin secretion.

There is compelling evidence for the involvement of hypothalamic-pituitary-adrenal (HPA) axis abnormalities in depression. Growing evidence has suggested that the combined dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test is highly sensitive to detect HPA axis abnormalities. We organized a multicenter study to assess the DEX/CRH test as a state-dependent marker for major depressive episode in the Japanese population. We conducted the DEX/CRH test in 61 inpatients with major depressive episode (Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV)) and 57 healthy subjects. In all, 35 patients were repeatedly assessed with the DEX/CRH test on admission and before discharge. The possible relationships between clinical variables and the DEX/CRH test were also examined. Significantly enhanced pituitary-adrenocortical responses to the DEX/CRH test were observed in patients on admission compared with controls. Such abnormalities in patients were significantly reduced after treatment, particularly in those who underwent electroconvulsive therapy (ECT) in addition to pharmacotherapy. Age and female gender were associated with enhanced hormonal responses to the DEX/CRH test. Severity of depression correlated with DEX/CRH test results, although this was explained, at least in part, by a positive correlation between age and severity in our patients. Medication per se was unrelated to DEX/CRH test results. These results suggest that the DEX/CRH test is a sensitive state-dependent marker to monitor HPA axis abnormalities in major depressive episode during treatment. Restoration from HPA axis abnormalities occurred with clinical responses to treatment, particularly in depressed patients who underwent ECT.

We report the first isolation of progenitor cells from the hypothalamus, a derivative of the embryonic basal plate that does not exhibit neurogenesis postnatally. Neurons derived from hypothalamic progenitor cells were compared with those derived from progenitor cultures of hippocampus, an embryonic alar plate derivative that continues to support neurogenesis in vivo into adulthood. Aside from their different embryonic origins and their different neurogenic potential in vivo, these brain regions were chosen because they are populated with cells of three different categories: Category I cells are generated in both hippocampus and hypothalamus, Category II cells are generated in the hypothalamus but are absent from the hippocampus, and Category III is a cell type generated in the olfactory placode that migrates into the hypothalamus during development. Stem-like cells isolated from other brain regions, with the ability to generate neurons and glia, produce neurons of several phenotypes including gabaergic, dopaminergic, and cholinergic lineages. In the present study, we extended our observations into neuroendocrine phenotypes. The cultured neural precursors from 7-week-old rat hypothalamus readily generated neuropeptide-expressing neurons. Hippocampal and hypothalamic progenitor cultures converged to indistinguishable populations and produced neurons of all three categories, confirming that even short-term culture confers or selects for immature progenitors with enough plasticity to elaborate neuronal phenotypes usually inhibited in vivo by the local microenvironment. The range of phenotypes generated from neuronal precursors in vitro now includes the peptides found in the neuroendocrine system: corticotropin-releasing hormone, growth hormone-releasing hormone, gonadotropin-releasing hormone, oxytocin, somatostatin, thyrotropin-releasing hormone, and vasopressin.

Seventy-two long-surviving liver transplant recipients were evaluated prospectively, including a baseline allograft biopsy for weaning off of immunosuppression. Thirteen were removed from candidacy because of chronic rejection (n = 4), hepatitis (n = 2), patient anxiety (n = 5), or lack of cooperation by the local physician (n = 2). The other 59, aged 12-68 years, had stepwise drug weaning with weekly or biweekly monitoring of liver function tests. Their original diagnoses were PBC (n = 9), HCC (n = 1), Wilson's disease (n = 4), hepatitides (n = 15), Laennec's cirrhosis (n = 1), biliary atresia (n = 16), cystic fibrosis (n = 1), hemochromatosis (n = 1), hepatic trauma (n = 1), alpha-1-antitrypsin deficiency (n = 9), and secondary biliary cirrhosis (n = 1). Most of the patients had complications of long-term immunosuppression, of which the most significant were renal dysfunction (n = 8), squamous cell carcinoma (n = 2) or verruca vulgaris of skin (n = 9), osteoporosis and/or arthritis (n = 12), obesity (n = 3), hypertension (n = 11), and opportunistic infections (n = 2). When azathioprine was a third drug, it was stopped first. Otherwise, weaning began with prednisone, using the results of corticotropin stimulation testing as a guide. If adrenal insufficiency was diagnosed, patients reduced to < 5 mg/day prednisone were considered off of steroids. The baseline agents (azathioprine, cyclosporine, or FK506) were then gradually reduced in monthly decrements. Complete weaning was accomplished in 16 patients (27.1%) with 3-19 months drug-free follow-up, is progressing in 28 (47.4%), and failed in 15 (25.4%) without graft losses or demonstrable loss of graft function from the rejections. This and our previous experience with self-weaned and other patients off of immunosuppression indicate that a significant percentage of appropriately selected long-surviving liver recipients can unknowingly achieve drug-free graft acceptance. Such attempts should not be contemplated until 5-10 years posttransplantation and then only with careful case selection, close monitoring, and prompt reinstitution of immunosuppression when necessary.

Major depression, with its strikingly high prevalence, is the most common cause of disability in communities of Western type, according to data of the World Health Organization. Stress-related mood disorders, besides their deleterious effects on the patient itself, also challenge the healthcare systems with their great social and economic impact. Our knowledge on the neurobiology of these conditions is less than sufficient as exemplified by the high proportion of patients who do not respond to currently available medications targeting monoaminergic systems. The search for new therapeutical strategies became therefore a "hot topic" in neuroscience, and there is a large body of evidence suggesting that brain neuropeptides not only participate is stress physiology, but they may also have clinical relevance. Based on data obtained in animal studies, neuropeptides and their receptors might be targeted by new candidate neuropharmacons with the hope that they will become important and effective tools in the management of stress related mood disorders. In this review, we attempt to summarize the latest evidence obtained using animal models for mood disorders, genetically modified rodent models for anxiety and depression, and we will pay some attention to previously published clinical data on corticotropin releasing factor, urocortin 1, urocortin 2, urocortin 3, arginine-vasopressin, neuropeptide Y, pituitary adenylate-cyclase activating polypeptide, neuropeptide S, oxytocin, substance P and galanin fields of stress research.

The estrogen 17β-estradiol (E2) modulates dendritic spine plasticity in the cornu ammonis 1 (CA1) region of the hippocampus, and GPR30 (G-protein coupled estrogen receptor 1 (GPER1)) is an estrogen-sensitive G-protein-coupled receptor (GPCR) that is expressed in the mammalian brain and in specific subregions that are responsive to E2, including the hippocampus. The subcellular localization of hippocampal GPR30, however, remains unclear. Here, we demonstrate that GPR30 immunoreactivity is detected in dendritic spines of rat CA1 hippocampal neurons in vivo and that GPR30 protein can be found in rat brain synaptosomes. GPR30 immunoreactivity is identified at the post-synaptic density (PSD) and in the adjacent peri-synaptic zone, and GPR30 can associate with the spine scaffolding protein PSD-95 both in vitro and in vivo. This PSD-95 binding capacity of GPR30 is specific and determined by the receptor C-terminal tail that is both necessary and sufficient for PSD-95 interaction. The interaction with PSD-95 functions to increase GPR30 protein levels residing at the plasma membrane surface. GPR30 associates with the N-terminal tandem pair of PDZ domains in PSD-95, suggesting that PSD-95 may be involved in clustering GPR30 with other receptors in the hippocampus. We demonstrate that GPR30 has the potential to associate with additional post-synaptic GPCRs, including the membrane progestin receptor, the corticotropin releasing hormone receptor, and the 5HT1a serotonin receptor. These data demonstrate that GPR30 is well positioned in the dendritic spine compartment to integrate E2 sensitivity directly onto multiple inputs on synaptic activity and might begin to provide a molecular explanation as to how E2 modulates dendritic spine plasticity.

OBJECTIVE

All human leukocyte antigen (HLA)-DRB1 alleles associated with rheumatoid arthritis (RA) encode a conserved amino acid sequence (QKRAA, QRRAA, or RRRAA) at position 70-74 in the third hypervariable region (HVR3) of the DRbeta(1) chain, which is commonly called the shared epitope (SE). Several studies, however, have associated the HLA-DRB1 gene in RA severity and progression rather than with susceptibility. Moreover, the association with disease severity and presence of the SE varies among different ethnic populations. HLA-DRB1 alleles also influence the disease onset. In this manuscript, the role of the HLA genes in RA was examined.

METHODS

A retrospective review of the literature was conducted to analyze the influence of the HLA-class II genes on the susceptibility, severity and protection against RA.

RESULTS

The HLA-DRB1*0401/*0404 genotype was associated with a higher risk for early disease onset in more severe forms in patients from the United Kingdom (UK). In northwest Spain, RA onset under 40 years is strongly associated with HLA-DRB1*0401 and *0404. In contrast, RA onset above 60 years is associated with HLA-DRB1*01. The protection against RA linked to some HLA-DRB1 alleles encoding a DERAA sequence of amino acids at position 70-74 in the HVR3 of the DRbeta1 chain, and specifically aspartic acid (D) at position 70 of this chain, recently was confirmed in both UK and northwest Spanish populations. Besides HLA-class II, other genes may be implicated in RA. Polymorphism in the tumor necrosis factor (TNF) region seems to be associated with RA, even in patients without the HLA-DRB1 SE. However, other genes such as interleukin-1 (IL-1) and corticotropin-releasing hormone may play a role in susceptibility to RA.

CONCLUSIONS

The additive effect of various genes may account for the development of RA and its clinical severity.

A complex relationship exists between alcohol-drinking behavior and stress. Alcohol has anxiety-reducing properties and can relieve stress, while at the same time acting as a stressor and activating the body's stress response systems. In particular, chronic alcohol exposure and withdrawal can profoundly disturb the function of the body's neuroendocrine stress response system, the hypothalamic-pituitary-adrenocortical (HPA) axis. A hormone, corticotropin-releasing factor (CRF), which is produced and released from the hypothalamus and activates the pituitary in response to stress, plays a central role in the relationship between stress and alcohol dependence and withdrawal. Chronic alcohol exposure and withdrawal lead to changes in CRF activity both within the HPA axis and in extrahypothalamic brain sites. This may mediate the emergence of certain withdrawal symptoms, which in turn influence the susceptibility to relapse. Alcohol-related dysregulation of the HPA axis and altered CRF activity within brain stress-reward circuitry also may play a role in the escalation of alcohol consumption in alcohol-dependent individuals. Numerous mechanisms have been suggested to contribute to the relationship between alcohol dependence, stress, and drinking behavior. These include the stress hormones released by the adrenal glands in response to HPA axis activation (i.e., corticosteroids), neuromodulators known as neuroactive steroids, CRF, the neurotransmitter norepinephrine, and other stress-related molecules.

Stress causes or contributes to a huge variety of diseases and disorders. Recent evidence suggests obesity and other eating-related disorders may be among these. Immediately after a stressful event is experienced, there is a corticotropin-releasing-hormone (CRH)-mediated suppression of food intake. This diverts the body's resources away from the less pressing need to find and consume food, prioritizing fight, flight, or withdrawal behaviors so the stressful event can be dealt with. In the hours following this, however, there is a glucocorticoid-mediated stimulation of hunger and eating behavior. In the case of an acute stress that requires a physical response, such as a predator-prey interaction, this hypothalamic-pituitary-adrenal (HPA) axis modulation of food intake allows the stressful event to be dealt with and the energy used to be replaced afterward. In the case of ongoing psychological stress, however, chronically elevated glucocorticoids can lead to chronically stimulated eating behavior and excessive weight gain. In particular, stress can enhance the propensity to eat high calorie "palatable" food via its interaction with central reward pathways. Activation of this circuitry can also interact with the HPA axis to suppress its further activation, meaning not only can stress encourage eating behavior, but eating can suppress the HPA axis and the feeling of stress. In this review we will explore the theme of eating behavior and stress and how these can modulate one another. We will address the interactions between the HPA axis and eating, introducing a potential integrative role for the orexigenic hormone, ghrelin. We will also examine early life and epigenetic modulation of the HPA axis and how this can influence eating behavior. Finally, we will investigate the clinical implications of changes to HPA axis function and how this may be contributing to obesity in our society.

Interest in developing a greater understanding of the pathophysiogical mechanisms underlying primary insomnia has increased. Recent evidence indicates that there may be some neuroendocrine and clinical similarities between primary insomnia and major depressive disorder, that abnormal corticotropin releasing factor (CRF) activity occurs in major depression, and that CRF hyperactivity appears to mediate the hyperarousal seen in primary insomnia. These findings all point to the possibility of hypothalamic-pituitary-adrenal (HPA) axis and CRF overactivity in both disorders. More recent findings have strengthened the evidence that primary insomnia may be linked with mood disorders and is associated with HPA axis overactivity and excess secretion of CRF, adrenocorticotropin releasing hormone, and cortisol. These insights have implications for managing chronic primary insomnia, such as use of antiglucocorticoid agents.

Glucagon is a 29-amino-acid peptide released from the α-cells of the islet of Langerhans, which has a key role in glucose homeostasis. Glucagon action is transduced by the class B G-protein-coupled glucagon receptor (GCGR), which is located on liver, kidney, intestinal smooth muscle, brain, adipose tissue, heart and pancreas cells, and this receptor has been considered an important drug target in the treatment of diabetes. Administration of recently identified small-molecule GCGR antagonists in patients with type 2 diabetes results in a substantial reduction of fasting and postprandial glucose concentrations. Although an X-ray structure of the transmembrane domain of the GCGR has previously been solved, the ligand (NNC0640) was not resolved. Here we report the 2.5 Å structure of human GCGR in complex with the antagonist MK-0893 (ref. 4), which is found to bind to an allosteric site outside the seven transmembrane (7TM) helical bundle in a position between TM6 and TM7 extending into the lipid bilayer. Mutagenesis of key residues identified in the X-ray structure confirms their role in the binding of MK-0893 to the receptor. The unexpected position of the binding site for MK-0893, which is structurally similar to other GCGR antagonists, suggests that glucagon activation of the receptor is prevented by restriction of the outward helical movement of TM6 required for G-protein coupling. Structural knowledge of class B receptors is limited, with only one other ligand-binding site defined--for the corticotropin-releasing hormone receptor 1 (CRF1R)--which was located deep within the 7TM bundle. We describe a completely novel allosteric binding site for class B receptors, providing an opportunity for structure-based drug design for this receptor class and furthering our understanding of the mechanisms of activation of these receptors.

BACKGROUND

Acamprosate is approved for the treatment of alcoholism, but its mechanism of action remains unclear. Results of animal studies suggest that a persistent hyperglutamatergic state contributes to the pathogenesis of alcoholism and that acamprosate may exert its actions by intervening in this process. Human translation of these findings is lacking.

OBJECTIVE

To examine whether acamprosate modulates indices of central glutamate levels in recently abstinent alcohol-dependent patients as measured using proton nuclear magnetic resonance spectroscopy (¹H-MRS).

METHODS

A 4-week, double-blind, placebo-controlled, randomized controlled experimental medicine study, with ¹H-MRS measures obtained on days 4 and 25.

METHODS

An inpatient research unit at the NIH Clinical Center. Patients Thirty-three patients who met the DSM-IV criteria for alcohol dependence and who were admitted for medically supervised withdrawal from ongoing alcohol use. Intervention Four weeks of acamprosate (initial oral loading followed by 1998 mg daily) or matched placebo, initiated at the time of admission.

METHODS

The glutamate to creatine ratio as determined using single-voxel ¹H-MRS in the anterior cingulate. Exploratory neuroendocrine, biochemical, and behavioral outcomes were also collected, as were safety- and tolerability-related measures.

RESULTS

There was a highly significant suppression of the glutamate to creatine ratio across time by acamprosate (time × treatment interaction: F₁(,)₂₉ = 13.5, P < .001). Cerebrospinal fluid levels of glutamate obtained in a subset of patients 4 weeks into abstinence were uncorrelated with the MRS measures and unaffected by treatment but were strongly correlated (R² = 0.48, P < .001) with alcohol dependence severity. Other exploratory outcomes, including repeated dexamethasone-corticotropin-releasing hormone tests, and psychiatric ratings were unaffected. Among tolerability measures, gastrointestinal symptoms were significantly greater in acamprosate-treated individuals, in agreement with the established profile of acamprosate.

CONCLUSIONS

The MRS measures of central glutamate are reduced across time when acamprosate therapy is initiated at the onset of alcohol abstinence.

BACKGROUND

clinicaltrials.gov Identifier: NCT00106106.

A polypeptide was purified from rat hypothalamic extracts on the basis of its high intrinsic activity to release corticotropin (ACTH) from cultured rat anterior pituitary cells and its immunoactivity in a radioimmunoassay directed against the NH2 terminus (residues 4-20) of ovine hypothalamic corticotropin-releasing factor (CRF). Based on Edman degradation, peptide mapping, and amino acid analysis, the primary structure of this rat CRF was established to be: H-Ser-Glu-Glu-Pro-Pro-Ile-Ser-Leu-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Met-Ala-Arg-Ala-Glu-Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn-Arg-Lys-Leu-Met-Glu-Ile-Ile-NH2. The hypophysiotropic potency of synthetic rat CRF did not deviate significantly from the potencies of the isolated native peptide or of synthetic ovine CRF. The close structural relationship between rat and ovine hypothalamic CRF is indicated by an 83% sequence homology.

Central administration of corticotropin-releasing hormone increases anxiety-like behaviour and arousal in rodents, and increased anxiety-like behaviour has been shown in mice overproducing corticotropin-releasing hormone on an elevated plus maze and in a dark-light emergence task. However, evidence is accumulating that measures obtained from different anxiety tasks may reflect different aspects of anxiety-like behaviour in animals. We therefore tested mice overproducing corticotropin-releasing hormone in a battery of paradigms, studying spontaneous behaviour after a mild stressor, tasks of innate anxiety-like behaviour (light-dark box), lick suppression (Vogel conflict), conditioned fear, and forced swimming. Exploratory behaviour was studied in a 16-hole board task. Furthermore, pain threshold, water intake, locomotor activity and sensorimotor learning/co-ordination were tested to control for confounding factors. In line with previous findings, increased anxiety-like behaviour of transgenic mice was observed in the light-dark box paradigm. However, no differences were seen in the conflict paradigm. Conditioned fear was decreased 1 h but not 24 h after conditioning in transgenic mice, and immobility was decreased [corrected] in forced swimming in corticotropin-releasing hormone overexpressors. Locomotor activity in a novel open field and on the hole board was reduced in transgenics. Exploratory behaviour (hole pokes) was reduced during initial exploration of an unfamiliar hole board. Moreover, sensorimotor performance on a rotorod was impaired, and water intake was reduced in corticotropin-releasing hormone overproducing mice, while no changes were seen in nociception. No differences in locomotor activity were seen in a second group of mice, tested in a familiar open field. When these animals were challenged with diazepam, transgenic mice were less susceptible to the sedative effects of the drug on locomotor activity. These data suggest that corticotropin-releasing hormone overproduction leads to specific effects in a subset of anxiety paradigms, and that these transgenic mice suffer from a motor deficit in addition to altered anxiety-like behaviour/arousal.

Research suggests that endogenous corticotropin-releasing factor (CRF) in the amygdala plays a role in the expression of stress-induced behavior. This study examined in rats whether antagonism of CRF receptors in the central amygdala (CA) region using alpha-helical CRF9-41, a CRF antagonist, was effective in attenuating the occurrence of stress-induced freezing. Bilateral infusions of 50, 100, or 200 ng of the CRF antagonist were made in the CA region using 33-gauge cannula immediately prior to testing. Freezing was measured in two test conditions. In one condition, the effects of the CRF antagonist on freezing was assessed immediately after exposure to electric foot shock. In the other condition, freezing was examined in shock-experienced rats that were re-exposed to the shock environment. Results suggested that 50 and 100 ng of the CRF antagonist were effective in reducing the duration of freezing in the immediate post-shock period. In addition, the 100 ng dose produced a significant reduction in freezing duration after rats were re-exposed to the shock environment. Collectively, data suggest that antagonizing the action of endogenous CRF in the CA region contributes to a general alleviation of stress-induced freezing.

The influence of central injection of a new corticotropin releasing factor (CRF) antagonist, astressin, [cyclo(30-33)[D-Phe12,Nle21,38,Glu30,Lys33]r/ hCRF12-41)], on exogenous and endogenous CRF-induced gastric ileus and stimulation of bowel discharges was investigated in conscious rats. Intracisternal (ic) CRF (0.6 microg) reduced gastric emptying of a noncaloric solution to 17.1 +/- 4.9% compared with 50.1 +/- 4.6% in control group injected i.c. with vehicle. Astressin (1,3 and 10 microg, i.c.) dose dependently prevented ic CRF-induced delayed gastric emptying by 33, 100 and 100%, respectively, and had no effect on basal gastric emptying. Abdominal surgery with cecal manipulation (1 min) reduced gastric emptying to 19.8 +/- 5.5% 3 hr postsurgery compared with 59.9 +/- 5.2% after anesthesia alone plus i.c. vehicle. Astressin (1,3 and 10 microg, i.c.) prevented postoperative gastric ileus by 56, 93 and 92%, respectively. Intracerebroventricular CRF (0.6 microg) and water-avoidance stress stimulated pellet output (number/60 min) to 5 +/- 1 and 11 +/- 2, respectively, compared with no fecal pellet output after i.c.v. vehicle and no exposure to stress. Astressin (3 and 10 microg, i.c.v.) blocked exogenous CRF action by 47 and 63%, respectively, and colonic response to stress by 0 and 54%, respectively. These data indicate that astressin injected into the CSF at low doses (1-10 microg) has an antagonistic action against CRF and stress-related alterations of gastrointestinal motor function, without an intrinsic effect in these in vivo systems. Astressin may be a useful tool to explore functional CRF-dependent physiological pathways in specific brain nuclei.