Alcoholism is a complex behavioral disorder characterized by excessive consumption of ethanol, a narrowing of the behavioral repertoire toward excessive consumption, the development of tolerance and dependence, and impairment in social and occupational functioning. Animal models of the complete syndrome of alcoholism are difficult if not impossible to achieve, but validated animal models exist for many of the different components of the syndrome. Recent work has begun to define the neurocircuits responsible for the two major sources of reinforcement key to animal models of excessive ethanol intake: positive and negative reinforcement. Ethanol appears to interact with ethanol-sensitive elements within neuronal membranes that convey the specificity of neurochemical action. Ethanol reinforcement appears to be mediated by an activation of GABA-A receptors, release of opioid peptides, release of dopamine, inhibition of glutamate receptors, and interaction with serotonin systems. These neurocircuits may be altered by chronic ethanol administration as reflected by opposite effects during acute ethanol withdrawal and by the recruitment of other neurotransmitter systems such as the stress neuropeptide corticotropin-releasing factor. Future challenges will include a focus on understanding how these neuroadaptive changes convey vulnerability to relapse in animals with a history of ethanol dependence.

Intraperitoneal administration of human recombinant interleukin-1 (IL-1) to rats can increase blood levels of corticosterone and adrenocorticotropic hormone (ACTH). The route by which IL-1 affects pituitary-adrenal activity is unknown. That the IL-1-induced pituitary-adrenal activation involves an increased secretion of corticotropin-releasing factor (CRF) is indicated by three lines of evidence. First, immunoneutralization of CRF markedly attenuated the IL-1-induced increase of ACTH blood levels. Second, after blockade of fast axonal transport in hypothalamic neurons by colchicine, IL-1 administration decreased the CRF immunostaining in the median eminence, indicating an enhanced release of CRF in response to IL-1. Third, IL-1 did not stimulate ACTH release from primary cultures of anterior pituitary cells. These data further support the notion of the existence of an immunoregulatory feedback circuit between the immune system and the brain.

It is well established that individual rats exhibit marked differences in behavioral responses to a novel environment. Rats that exhibit high rates of locomotor activity and sustained exploration in such an environment also exhibit high concentrations of stress-induced plasma corticosterone, linking this behavior to the stress system. Furthermore, these high-responding (HR) rats, in contrast to their low-responding (LR) counterparts, have a greater propensity to self-administer drugs. Thus, HR rats have been described as "novelty" seeking in that they are more active and explore novel stimuli more vigorously, despite the fact that this elicits in them high stress responses. In this study, we have further characterized the behavior of HR and LR rats in tests of anxiety and characterized their stress responses to either experimenter- or self-imposed stressors. We then investigated the physiological basis of these individual differences, focusing on stress-related molecules, including the glucocorticoid receptor (GR), the mineralocorticoid receptor (MR), corticotropin-releasing hormone (CRH) and pro-opiomelanocortin (POMC) in the context of the limbic-hypothalamo-pituitary adrenal axis. We have found that HR rats did not differ from LR in their basal expression of POMC in the pituitary. However, HR rats exhibited higher levels of CRH mRNA in the hypothalamic paraventricular nucleus but lower basal levels in the central nucleus of the amygdala. The basal expression of hippocampal MR is not different between HR and LR rats. Interestingly, the basal expression of hippocampal GR mRNA is significantly lower in HR than in LR rats. This low level of hippocampal GR expression in HR rats appears to be responsible, at least in part, for their decreased anxiety in exploring novelty. Indeed, the anxiety level of LR rats becomes similar to HR rats after the administration into the hippocampus of a GR antagonist, RU38486. These data indicate that basal differences in gene expression of key stress-related molecules may play an important role in determining individual differences in responsiveness to stress and novelty. They point to a new role of hippocampal GR, strongly implicating this receptor in determining individual differences in anxiety and novelty-seeking behavior.

Clinical and preclinical data suggest that unrestrained secretion of corticoctropin-releasing hormone (CRH) in the CNS produces several signs and symptoms of depression and anxiety disorders through continuous activation of CRH(1) receptors. This led to the development of drugs that selectively antagonize CRH(1) receptors suppressing anxiety-like behavior in rats and also in monkey models of anxiety. These findings led to a clinical development program exploring the antidepressive potential of R121919, a water-soluble pyrrolopyrimidine that binds with high affinity to human CRH(1) receptors and is well absorbed in humans. This compound was administered to 24 patients with a major depressive episode primarily in order to investigate whether its endocrine mode of action compromises the stress-hormone system or whether other safety and tolerability issues exist. The patients were enrolled in two dose-escalation panels: one group (n=10) where the dose range increased from 5-40 mg and another group (n=10) where the dose escalated from 40 to 80 mg within 30 days each. Four patients dropped out because of withdrawal of consent to participate (three cases) or worsening of depressive symptomatoloy in one case. We found that R121919 was safe and well tolerated by the patients during the observation period. Moreover, the data suggested that CRH(1)-receptor blockade does not impair the corticotropin and cortisol secretory activity either at baseline or following an exogenous CRH challenge. We also observed significant reductions in depression and anxiety scores using both, patient and clinician ratings. These findings, along with the observed worsening of affective symptomatology after drug discontinuation, suggests that the pharmacological principle of CRH(1)-receptor antagonism has considerable therapeutic potential in the treatment and the prevention of diseases where exaggerated central CRH activity is present at baseline or following stress exposure.

Cortisol has been implicated as a pathophysiological mediator in idiopathic obesity, but circulating cortisol concentrations are not consistently elevated. The tissue-specific responses to cortisol may be influenced as much by local prereceptor metabolism as by circulating concentrations. For example, in liver and adipose tissue cortisol is regenerated from inactive cortisone by 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1). In obese Zucker rats 11beta-HSD1 activity is reduced in liver but enhanced in adipose tissue. This study addressed whether the same tissue-specific disruption of cortisol metabolism occurs in human obesity. 34 men were recruited from the MONICA population study in Northern Sweden to represent a wide range of body composition and insulin insensitivity. Plasma cortisol was measured at 0830h and 1230h, after overnight low-dose dexamethasone suppression, after intravenous corticotropin releasing hormone (CRH), and after oral cortisone administration. Urinary cortisol metabolites were measured in a 24 h sample. A subcutaneous fat biopsy was obtained from 16 participants to measure cortisol metabolism in vitro. Higher body mass index was associated with increased total cortisol metabolite excretion (r = 0.47, p < 0.01), but lower plasma cortisol at 1230 h and after dexamethasone, and no difference in response to CRH. Obese men excreted a greater proportion of glucocorticoid as metabolites of cortisone rather than cortisol (r = 0.43, p < 0.02), and converted less cortisone to cortisol after oral administration (r = 0.49, p < 0.01), suggesting impaired hepatic 11beta-HSD1 activity. By contrast, in vitro 11beta-HSD1 activity in subcutaneous adipose tissue was markedly enhanced in obese men (r = 0.66, p < 0.01). We conclude that in obesity, reactivation of cortisone to cortisol by 11beta-HSD1 in liver is impaired, so that plasma cortisol levels tend to fall, and there may be a compensatory increase in cortisol secretion mediated by a normally functioning hypothalamic-pituitary-adrenal axis. However, changes in 11beta-HSD1 are tissue-specific: strikingly enhanced reactivation of cortisone to cortisol in subcutaneous adipose tissue may exacerbate obesity; and it may be beneficial to inhibit this enzyme in adipose tissue in obese patients.

Although hypothalamic-pituitary-adrenal axis activation is generally considered to be the hallmark of the stress response, many of the same stimuli that initiate this response also activate the locus coeruleus-norepinephrine system. Given its functional attributes, the parallel engagement of the locus coeruleus-norepinephrine system with the hypothalamic-pituitary-adrenal axis serves to coordinate endocrine and cognitive limbs of the stress response. The elucidation of stress-related afferents to the locus coeruleus and the electrophysiological characterization of these inputs are revealing how the activity of this system is fine-tuned by stressors to facilitate adaptive cognitive responses. Emerging from these studies, is a picture of complex interactions between the stress-related neuropeptide, corticotropin-releasing factor (CRF), endogenous opioids and the excitatory amino acid neurotransmitter, glutamate. The net effect of these interactions is to adjust the activity and reactivity of the locus coeruleus-norepinephrine system such that state of arousal and processing of sensory stimuli are modified to facilitate adaptive behavioral responses to stressors. This review begins with an introduction to the basic anatomical and physiological characteristics of locus coeruleus neurons. The concept that locus coeruleus neurons operate through two activity modes, i.e., tonic vs. phasic, that determine distinct behavioral strategies is emphasized in light of its relevance to stress. Anatomical and physiological evidence are then presented suggesting that interactions between stress-related neurotransmitters that converge on locus coeruleus neurons regulate shifts between these modes of discharge in response to the challenge of a stressor. This review focuses specifically on the locus coeruleus because it is the major source of norepinephrine to the forebrain and has been implicated in behavioral and cognitive aspects of stress responses.

Alcoholism is a chronic relapsing disorder with substantial heritability. Uncovering gene-environment interactions underlying this disease process can aid identification of novel treatment targets. Here, we found a lowered threshold for stress-induced reinstatement of alcohol seeking in Marchigian-Sardinian Preferring (msP) rats genetically selected for high alcohol preference. In situ hybridization for a panel of 20 stress-related genes in 16 brain regions was used to screen for differential gene expression that may underlie this behavioral phenotype. An innate up-regulation of the Crhr1 transcript, encoding the corticotropin-releasing hormone receptor 1 (CRH-R1), was found in several limbic brain areas of msP rats genetically selected for high alcohol preference, was associated with genetic polymorphism of the Crhr1 promoter, and was accompanied by increased CRH-R1 density. A selective CRH-R1 antagonist (antalarmin, 10-20 mg/kg) was devoid of effects on operant alcohol self-administration in unselected Wistar rats but significantly suppressed this behavior in the msP line. Stress-induced reinstatement of alcohol seeking was not significantly affected by antalarmin in Wistar rats but was fully blocked in msP animals. These data demonstrate that Crhr1 genotype and expression interact with environmental stress to reinstate alcohol-seeking behavior.

Corticotropin-releasing hormone (CRH) is centrally involved in coordinating responses to a variety of stress-associated stimuli. Recent clinical data implicate CRH in the pathophysiology of human affective disorders. To differentiate the CNS pathways involving CRH and CRH receptor 1 (Crhr1) that modulate behavior from those that regulate neuroendocrine function, we generated a conditional knockout mouse line (Crhr1(loxP/loxP)Camk2a-cre) in which Crhr1 function is inactivated postnatally in anterior forebrain and limbic brain structures, but not in the pituitary. This leaves the hypothalamic-pituitary-adrenocortical (HPA) system intact. Crhr1(loxP/loxP)Camk2a-cre mutants showed reduced anxiety, and the basal activity of their HPA system was normal. In contrast to Crhr1 null mutants, conditional mutants were hypersensitive to stress corticotropin and corticosterone levels remained significantly elevated after stress. Our data clearly show that limbic Crhr1 modulates anxiety-related behavior and that this effect is independent of HPA system function. Furthermore, we provide evidence for a new role of limbic Crhr1 in neuroendocrine adaptation to stress.

We describe a novel corticotropin-releasing factor receptor 1 (CRF1) antagonist with advantageous properties for clinical development, and its in vivo activity in preclinical alcoholism models. 3-(4-Chloro-2-morpholin-4-yl-thiazol-5-yl)-8-(1-ethylpropyl)-2,6-dimethyl-imidazo[1,2-b]pyridazine (MTIP) inhibited 125I-sauvagine binding to rat pituitary membranes and cloned human CRF1 with subnanomolar affinities, with no detectable activity at the CRF2 receptor or other common drug targets. After oral administration to rats, MTIP inhibited 125I-sauvagine binding to rat cerebellar membranes ex vivo with an ED50 of approximately 1.3 mg/kg and an oral bioavailability of 91.1%. Compared with R121919 (2,5-dimethyl-3-(6-dimethyl-4-methylpyridin-3-yl)-7-dipropylamino-pyrazolo[1,5-a]pyrimidine) and CP154526 (N-butyl-N-ethyl-4,9-dimethyl-7-(2,4,6-trimethylphenyl)-3,5,7-triazabicyclo[4.3.0]nona-2,4,8,10-tetraen-2-amine), MTIP had a markedly reduced volume of distribution and clearance. Neither open-field activity nor baseline exploration of an elevated plus-maze was affected by MTIP (1-10 mg/kg). In contrast, MTIP dose-dependently reversed anxiogenic effects of withdrawal from a 3 g/kg alcohol dose. Similarly, MTIP blocked excessive alcohol self-administration in Wistar rats with a history of dependence, and in a genetic model of high alcohol preference, the msP rat, at doses that had no effect in nondependent Wistar rats. Also, MTIP blocked reinstatement of stress-induced alcohol seeking both in postdependent and in genetically selected msP animals, again at doses that were ineffective in nondependent Wistar rats. Based on these findings, MTIP is a promising candidate for treatment of alcohol dependence.

The stress response is mediated by the hypothalamo-pituitary-adrenal (HPA) system. Activity of the corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN) forms the basis of the activity of the HPA-axis. The CRH neurons induce adrenocorticotropin (ACTH) release from the pituitary, which subsequently causes cortisol release from the adrenal cortex. The CRH neurons co-express vasopressin (AVP) which potentiates the CRH effects. CRH neurons project not only to the median eminence but also into brain areas where they, e.g., regulate the adrenal innervation of the autonomic system and affect mood. The hypothalamo-neurohypophysial system is also involved in stress response. It releases AVP from the PVN and the supraoptic nucleus (SON) and oxytocin (OXT) from the PVN via the neurohypophysis into the bloodstream. The suprachiasmatic nucleus (SCN), the hypothalamic clock, is responsible for the rhythmic changes of the stress system. Both centrally released CRH and increased levels of cortisol contribute to the signs and symptoms of depression. Symptoms of depression can be induced in experimental animals by intracerebroventricular injection of CRH. Depression is also a frequent side effect of glucocorticoid treatment and of the symptoms of Cushing's syndrome. The AVP neurons in the hypothalamic PVN and SON are also activated in depression, which contributes to the increased release of ACTH from the pituitary. Increased levels of circulating AVP are also associated with the risk for suicide. The prevalence, incidence and morbidity risk for depression are higher in females than in males and fluctuations in sex hormone levels are considered to be involved in the etiology. About 40% of the activated CRH neurons in mood disorders co-express nuclear estrogen receptor (ER)-alpha in the PVN, while estrogen-responsive elements have been found in the CRH gene promoter region, and estrogens stimulate CRH production. An androgen-responsive element in the CRH gene promoter region initiates a suppressing effect on CRH expression. The decreased activity of the SCN is the basis for the disturbances of circadian and circannual fluctuations in mood, sleep and hormonal rhythms found in depression. Neuronal loss was also reported in the hippocampus of stressed or corticosteroid-treated rodents and primates. Because of the inhibitory control of the hippocampus on the HPA-axis, damage to this structure was expected to disinhibit the HPA-axis, and to cause a positive feedforward cascade of increasing glucocorticoid levels over time. This 'glucocorticoid cascade hypothesis' of stress and hippocampal damage was proposed to be causally involved in age-related accumulation of hippocampal damage in disorders like Alzheimer's disease and depression. However, in postmortem studies we could not find the presumed hippocampal damage of steroid overexposure in either depressed patients or in patients treated with synthetic steroids.

Dysregulation of the brain emotional systems that mediate arousal and stress is a key component of the pathophysiology of drug addiction. Drug addiction is a chronically relapsing disorder characterized by a compulsion to seek and take drugs and the development of dependence and manifestation of a negative emotional state when the drug is removed. Activation of brain stress systems is hypothesized to be a key element of the negative emotional state produced by dependence that drives drug-seeking through negative reinforcement mechanisms. The focus of the present review is on the role of two key brain arousal/stress systems in the development of dependence. Emphasis is placed on the neuropharmacological actions of corticotropin-releasing factor (CRF) and norepinephrine in extrahypothalamic systems in the extended amygdala, including the central nucleus of the amygdala, bed nucleus of the stria terminalis, and a transition area in the shell of the nucleus accumbens. Compelling evidence argues that these brain stress systems, a heretofore largely neglected component of dependence and addiction, play a key role in engaging the transition to dependence and maintaining dependence once it is initiated. Understanding the role of the brain stress and anti-stress systems in addiction not only provides insight into the neurobiology of the "dark side" of addiction but also provides insight into the organization and function of basic brain emotional circuitry that guides motivated behavior.

The hypothalamo-pituitary-adrenal (HPA) axis is known to be activated in depressed patients. Although direct evidence is lacking, this activation is hypothesized to be due to hyperactivity of corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus (PVN). Recent immunocytochemical studies in experimental animals and in humans showed that the number of CRH-expressing neurons correlated with the activity of these neurons. In addition, colocalization of AVP in CRH neurons has been shown to be an index for the secretory activity. Therefore, we estimated the total number of CRH-immunoreactive neurons and their fraction showing colocalization with AVP in the PVN of 10 control subjects and of 6 depressed patients who were diagnosed to be suffering from a major depression or a bipolar disorder. The mean total number of CRH-expressing neurons of the 6 depressed patients was four times higher, and the number of CRH neurons co-expressing AVP was almost three times higher than those in the control group. We also determined the two activity parameters of CRH neurons in the PVN of 2 subjects with a depressive organic mood syndrome or a depressive disorder not otherwise specified. In these two 'non-major depressed' subjects, the activity parameters of CRH neurons were comparable to those of control subjects. Our observations strongly support the hypothesis that CRH neurons in the PVN are hyperactivated in major depressed patients. This hyperactivity might be causally related to at least part of the symptomatology of depression.

Corticotropin-releasing factor (CRF) and the related urocortin peptides mediate behavioral, cognitive, autonomic, neuroendocrine and immunologic responses to aversive stimuli by activating CRF(1) or CRF(2) receptors in the central nervous system and anterior pituitary. Markers of hyperactive central CRF systems, including CRF hypersecretion and abnormal hypothalamic-pituitary-adrenal axis functioning, have been identified in subpopulations of patients with anxiety, stress and depressive disorders. Because CRF receptors are rapidly desensitized in the presence of high agonist concentrations, CRF hypersecretion alone may be insufficient to account for the enhanced CRF neurotransmission observed in these patients. Concomitant dysregulation of mechanisms stringently controlling magnitude and duration of CRF receptor signaling also may contribute to this phenomenon. While it is well established that the CRF(1) receptor mediates many anxiety- and depression-like behaviors as well as HPA axis stress responses, CRF(2) receptor functions are not well understood at present. One hypothesis holds that CRF(1) receptor activation initiates fear and anxiety-like responses, while CRF(2) receptor activation re-establishes homeostasis by counteracting the aversive effects of CRF(1) receptor signaling. An alternative hypothesis posits that CRF(1) and CRF(2) receptors contribute to opposite defensive modes, with CRF(1) receptors mediating active defensive responses triggered by escapable stressors, and CRF(2) receptors mediating anxiety- and depression-like responses induced by inescapable, uncontrollable stressors. CRF(1) receptor antagonists are being developed as novel treatments for affective and stress disorders. If it is confirmed that the CRF(2) receptor contributes importantly to anxiety and depression, the development of small molecule CRF(2) receptor antagonists would be therapeutically useful.

BACKGROUND

We reported previously that bilateral injection of a corticotropin-releasing factor (CRF)-receptor antagonist, D-Phe CRF(12-41), into the bed nucleus of the stria terminalis (BNST) blocks the reinstatement of cocaine seeking induced by footshock, whereas the injection of CRF into the same region induces reinstatement. One source of CRF in the BNST arises from a CRF-containing projection originating in the central nucleus of the amygdala (CeA).

OBJECTIVE

To determine whether the CRF-containing projection from the amygdala to the BNST is involved in the mediation of stress-induced reinstatement of cocaine seeking by functionally interrupting the pathway.

METHODS

Rats trained to self-administer cocaine (1 mg/kg, IV, 9 days) were given extinction sessions after a 10- to 11-day drug-free period, followed by tests for stress-induced reinstatement (footshock: 15 min intermittent 0.8-mA footshocks given immediately before presentation of the previously active lever). Before the tests, animals were pretreated with either: (1) TTX (2.5 ng) in amygdala (including the CeA) in one hemisphere and D-Phe CRF(12-41) (50 ng) in BNST in the other, (2) unilateral TTX, or (3) unilateral D-Phe.

RESULTS

Footshock reinstated cocaine seeking following unilateral injections of either TTX in amygdala or D-Phe in BNST, but following the injection of both TTX in amygdala and D-Phe in BNST the effects of footshock were greatly attenuated.

CONCLUSIONS

These results suggest that the CRF-containing pathway from CeA to BNST is involved in mediating the effects of CRF and its receptor antagonist in the BNST on the reinstatement of cocaine seeking.

BACKGROUND

Corticotropin-releasing factor (CRF) and gamma-aminobutyric acid (GABA)ergic systems in the central amygdala (CeA) are implicated in the high-anxiety, high-drinking profile associated with ethanol dependence. Ethanol augments CeA GABA release in ethanol-naive rats and mice.

METHODS

Using naive and ethanol-dependent rats, we compared electrophysiologic effects and interactions of CRF and ethanol on CeA GABAergic transmission, and we measured GABA dialyzate in CeA after injection of CRF(1) antagonists and ethanol. We also compared mRNA expression in CeA for CRF and CRF(1) using real-time polymerase chain reaction. We assessed effects of chronic treatment with a CRF(1) antagonist on withdrawal-induced increases in alcohol consumption in dependent rats.

RESULTS

CRF and ethanol augmented CeA GABAergic transmission in naive rats via increased GABA release. Three CRF1 receptor (CRF(1)) antagonists decreased basal GABAergic responses and abolished ethanol effects. Ethanol-dependent rats exhibited heightened sensitivity to CRF and CRF(1) antagonists on CeA GABA release. Intra-CeA CRF(1) antagonist administration reversed dependence-related elevations in GABA dialysate and blocked ethanol-induced increases in GABA dialyzate in both dependent and naive rats. Polymerase chain reaction studies indicate increased expression of CRF and CRF(1) in CeA of dependent rats. Chronic CRF(1) antagonist treatment blocked withdrawal-induced increases in alcohol drinking by dependent rats and tempered moderate increases in alcohol consumption by nondependent rats in intermittent testing.

CONCLUSIONS

These combined findings suggest a key role for specific presynaptic CRF-GABA interactions in CeA in the development and maintenance of ethanol dependence.

Inbred Lewis (LEW/N) female rats develop an arthritis in response to group A streptococcal cell wall peptidoglycan polysaccharide (SCW), which mimics human rheumatoid arthritis. Histocompatible Fischer (F344/N) rats do not develop arthritis in response to the same SCW stimulus. To evaluate this difference in inflammatory reactivity, we examined the function of the hypothalamic-pituitary-adrenal (HPA) axis and its ability to modulate the development of the inflammatory response in LEW/N and F344/N rats. We have found that, in contrast to F344/N rats, LEW/N rats had markedly impaired plasma corticotropin and corticosterone responses to SCW, recombinant human interleukin 1 alpha, the serotonin agonist quipazine, and synthetic rat/human corticotropin-releasing hormone. LEW/N rats also had smaller adrenal glands and larger thymuses. Replacement doses of dexamethasone decreased the severity of LEW/N rats' SCW-induced arthritis. Conversely, treatment of F344/N rats with the glucocorticoid receptor antagonist RU 486 or the serotonin antagonist LY53857 was associated with development of severe inflammatory disease, including arthritis, in response to SCW. These findings support the concept that susceptibility of LEW/N rats to SCW arthritis is related to defective HPA axis responsiveness to inflammatory and other stress mediators and that resistance of F344/N rats to SCW arthritis is regulated by an intact HPA axis-immune system feedback loop.

There is increasing evidence for an important role of adverse early experience on the development of major psychiatric disorders in adulthood. Corticotropin-releasing factor (CRF), an endogenous neuropeptide, is the primary physiological regulator of the mammalian stress response. Grown nonhuman primates who were exposed as infants to adverse early rearing conditions were studied to determine if long-term alterations of CRF neuronal systems had occurred following the early stressor. In comparison to monkeys reared by mothers foraging under predictable conditions, infant monkeys raised by mothers foraging under unpredictable conditions exhibited persistently elevated cerebrospinal fluid (CSF) concentrations of CRF. Because hyperactivity of CRF-releasing neurons has been implicated in the pathophysiology of certain human affective and anxiety disorders, the present finding provides a potential neurobiological mechanism by which early-life stressors may contribute to adult psychopathology.

We report the existence of a 'placental clock', which is active from an early stage in human pregnancy and determines the length of gestation and the timing of parturition and delivery. Using a prospective, longitudinal cohort study of 485 pregnant women we have demonstrated that placental secretion of corticotropin-releasing hormone (CRH) is a marker of this process and that measurement of the maternal plasma CRH concentration as early as 16-20 weeks of gestation identifies groups of women who are destined to experience normal term, preterm or post-term delivery. Further, we report that the exponential rise in maternal plasma CRH concentrations with advancing pregnancy is associated with a concomitant fall in concentrations of the specific CRH binding protein in late pregnancy, leading to a rapid increase in circulating levels of bioavailable CRH at a time that coincides with the onset of parturition, suggesting that CRH may act directly as a trigger for parturition in humans.

BACKGROUND

Alcoholism is a chronic, relapsing illness in which stress and alcohol cues contribute significantly to relapse risk. Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, increased anxiety, and high alcohol craving have been documented during early alcohol recovery, but their influence on relapse risk has not been well studied.

OBJECTIVE

To investigate these responses in treatment-engaged, 1-month-abstinent, recovering alcohol-dependent patients relative to matched controls (study 1) and to assess whether HPA axis function, anxiety, and craving responses are predictive of subsequent alcohol relapse and treatment outcome (study 2).

METHODS

Experimental exposure to stress, alcohol cues, and neutral, relaxing context to provoke alcohol craving, anxiety, and HPA axis responses (corticotropin and cortisol levels and cortisol to corticotropin ratio) and a prospective 90-day follow-up outcome design to assess alcohol relapse and aftercare treatment outcomes.

METHODS

Inpatient treatment in a community mental health center and hospital-based research unit.

METHODS

Treatment-engaged alcohol-dependent individuals and healthy controls.

METHODS

Time to alcohol relapse and to heavy drinking relapse.

RESULTS

Significant HPA axis dysregulation, marked by higher basal corticotropin level and lack of stress- and cue-induced corticotropin and cortisol responses, higher anxiety, and greater stress- and cue-induced alcohol craving, was seen in the alcohol-dependent patients vs the control group. Stress- and cue-induced anxiety and stress-induced alcohol craving were associated with fewer days in aftercare alcohol treatment. High provoked alcohol craving to both stress and to cues and greater neutral, relaxed-state cortisol to corticotropin ratio (adrenal sensitivity) were each predictive of shorter time to alcohol relapse.

CONCLUSIONS

These results identify a significant effect of high adrenal sensitivity, anxiety, and increased stress- and cue-induced alcohol craving on subsequent alcohol relapse and treatment outcomes. Findings suggest that new treatments that decrease adrenal sensitivity, stress- and cue-induced alcohol craving, and anxiety could be beneficial in improving alcohol relapse outcomes.

The medial prefrontal cortex (mPFC) is an important neural substrate for integrating cognitive-affective information and regulating the hypothalamo-pituitary-adrenal (HPA) axis response to emotional stress. mPFC modulation of stress responses is effected in part via the paraventricular hypothalamic nucleus (PVH), which houses both autonomic (sympathoadrenal) and neuroendocrine (HPA) effector mechanisms. Although the weight of evidence suggests that mPFC influences on stress-related PVH outputs are inhibitory, discordant findings have been reported, and such work has tended to treat this cortical region as a unitary structure. Here we compared the effects of lesions of the dorsal versus ventral aspects of mPFC, centered in the prelimbic and infralimbic fields, respectively, on acute restraint stress-induced activation of PVH cell groups mediating autonomic and neuroendocrine responses. Lesions to the dorsal mPFC enhanced restraint-induced Fos and corticotropin-releasing factor (CRF) mRNA expression in the neurosecretory region of PVH. Ablation of the ventral mPFC decreased stress-induced Fos protein and CRF mRNA expression in this compartment but increased Fos induction in PVH regions involved in central autonomic control. Repetition of the experiments in rats bearing retrograde tracer deposits to label PVH-autonomic projections confirmed that ventral mPFC lesions selectively increased stress-induced Fos expression in identified preautonomic neurons. Finally, hormonal indices of HPA activation in response to acute stress were augmented after dorsal mPFC lesions and attenuated after ventral mPFC lesions. These results suggest that dorsal and ventral aspects of the mPFC differentially regulate neuroendocrine and autonomic PVH outputs in response to emotional stress.

Stress increases addictive behaviors and is a common cause of relapse. Corticotropin-releasing factor (CRF) plays a key role in the modulation of drug taking by stress. However, the mechanism by which CRF modulates neuronal activity in circuits involved in drug addiction is poorly understood. Here we show that CRF induces a potentiation of NMDAR (N-methyl-D-aspartate receptor)-mediated synaptic transmission in dopamine neurons of the ventral tegmental area (VTA). This effect involves CRF receptor 2 (CRF-R2) and activation of the phospholipase C (PLC)-protein kinase C (PKC) pathway. We also find that this potentiation requires CRF binding protein (CRF-BP). Accordingly, CRF-like peptides, which do not bind the CRF-BP with high affinity, do not potentiate NMDARs. These results provide evidence of the first specific roles for CRF-R2 and CRF-BP in the modulation of neuronal activity and suggest that NMDARs in the VTA may be a target for both drugs of abuse and stress.

Mutations reducing the functional activity of leptin, the leptin receptor, alpha-melanocyte stimulating hormones (alpha-MSH) and the melanocortin-4 receptor (Mc4r) all lead to obesity in mammals. Moreover, mutant mice that ectopically express either agouti (Ay/a mice) or agouti-related protein (Agrp), antagonists of melanocortin signalling, become obese. These data suggest that alpha-MSH signalling transduced by Mc4r tonically inhibits feeding; however, it is not known to what extent this pathway mediates leptin signalling. We show here that Mc4r-deficient (Mc4r-/-) mice do not respond to the anorectic actions of MTII, an MSH-like agonist, suggesting that alpha-MSH inhibits feeding primarily by activating Mc4r. Obese Mc4r-/-mice do not respond significantly to the inhibitory effects of leptin on feeding, whereas non-obese Mc4r-/- mice do. These data demonstrate that melanocortin signalling transduced by Mc4r is not an exclusive target of leptin action and that factors resulting from obesity contribute to leptin resistance. Leptin resistance of obese Mc4r-/- mice does not prevent their response to the anorectic actions of ciliary neurotrophic factor (CNTF), corticotropin releasing factor (CRF), or urocortin; or the orexigenic actions of neuropeptide Y (NPY) or peptide YY (PYY), indicating that these neuromodulators act independently or downstream of Mc4r signalling.

The medial division of the central nucleus of the amygdala (CeA(M)) and the lateral division of the bed nucleus of the stria terminalis (BNST(L)) are closely related. Both receive projections from the basolateral amygdala (BLA) and both project to brain areas that mediate fear-influenced behaviors. In contrast to CeA(M) however, initial attempts to implicate the BNST in conditioned fear responses were largely unsuccessful. More recent studies have shown that the BNST does participate in some types of anxiety and stress responses. Here, we review evidence suggesting that the CeA(M) and BNST(L) are functionally complementary, with CeA(M) mediating short- but not long-duration threat responses (i.e., phasic fear) and BNST(L) mediating long- but not short-duration responses (sustained fear or 'anxiety'). We also review findings implicating the stress-related peptide corticotropin-releasing factor (CRF) in sustained but not phasic threat responses, and attempt to integrate these findings into a neural circuit model which accounts for these and related observations.

The hypothalamic neuropeptides hypocretins (orexins) play a crucial role in the stability of arousal and alertness. We tested whether the hypocretinergic system is a critical component of the stress response activated by the corticotropin-releasing factor (CRF). Our results show that CRF-immunoreactive terminals make direct contact with hypocretin-expressing neurons in the lateral hypothalamus and that numerous hypocretinergic neurons express the CRF-R1/2 receptors. We also demonstrate that application of CRF to hypothalamic slices containing identified hypocretin neurons depolarizes membrane potential and increases firing rate in a subpopulation of hypocretinergic cells. CRF-induced depolarization was tetrodotoxin insensitive and was blocked by the peptidergic CRF-R1 antagonist astressin. Moreover, activation of hypocretinergic neurons in response to acute stress was severely impaired in CRF-R1 knock-out mice. Together, our data provide evidence of a direct neuroanatomical and physiological input from CRF peptidergic system onto hypocretin neurons. We propose that, after stressor stimuli, CRF stimulates the release of hypocretins and that this circuit contributes to activation and maintenance of arousal associated with the stress response.