Pharmacological blockade of corticotropin-releasing hormone receptor 1 (CRH1R) reduces voluntary consumption of high alcohol concentrations in non-dependent Wistar rats.

A dysregulation of the corticotropin-releasing hormone (CRH) system has been implicated in the development of excessive alcohol consumption and dependence. The aim of the present study was to evaluate whether the CRH system is also recruited when non-dependent Wistar rats escalate to high alcohol intake in the intermittent (alternate days) model of drinking. METHODS: We compared intermittent and continuous access to 20% (v/v) alcohol in a two-bottle free choice drinking paradigm. Following a total of twenty 24-hour exposures for every experimental group, we assessed signs of alcohol withdrawal, including anxiety-like behavior and sensitivity to stress. The selective CRH1 receptor (CRH1R) antagonist antalarmin (0, 10, 20 mg/kg, i.p.) was tested on alcohol consumption. RESULTS: Intermittent access to 20% alcohol led non-selected Wistar rats to escalate their voluntary intake to a high and stable level, whereas continuously exposed animals maintained a lower consumption. These groups did not differ in physical withdrawal signs. In addition, no differences were found when anxiogenic-like behavior was studied, neither under basal conditions or following restraint stress. Nevertheless, sensitivity to the treatment with the CRH1R antalarmin was observed since a reduction of 20% alcohol intake was found in both groups of animals regardless of the regimen of alcohol exposure. In addition, antalarmin was effective when injected to animals exposed to intermittent 10% (v/v) alcohol whereas it failed to suppress 10% continuous alcohol intake. CONCLUSIONS: Pharmacological blockade of CRH1R reduced alcohol drinking when sustained high levels of intake were achieved suggesting that the CRH system plays a key role when high doses of ethanol are consumed by non-dependent subjects. This supports the notion that CRH system not only maintains the dependent state but also engages the transition to dependence

Long-term suppression of forebrain neurogenesis and loss of neuronal progenitor cells following prolonged alcohol dependence in rats.

Alcohol dependence leads to persistent neuroadaptations, potentially related to structural plasticity. Previous work has shown that hippocampal neurogenesis is modulated by alcohol, but effects of chronic alcohol on neurogenesis in the forebrain subventricular zone (SVZ) have not been reported. Effects in this region may be relevant for the impairments in olfactory discrimination present in alcoholism. Here, we examined the effects of prolonged alcohol dependence on neurogenesis. Rats were sacrificed directly after 7 wk of intermittent alcohol vapour exposure, or 3, 7 or 21 d into abstinence. Proliferation was assessed using BrdU and Ki67 immunoreactivity, newly differentiated neurons (neurogenesis) as doublecortin-immunoreactivity (DCX-IR), and neural stem cells using the SOX2 marker. In the dentate gyrus, chronic dependence resulted in a pattern similar to that previously reported for acute alcohol exposure: proliferation and neurogenesis were suppressed by the end of exposure, rebounded on day 3 of abstinence, and returned to control levels by days 7 and 21. In the SVZ, proliferation was also suppressed at the end of alcohol exposure, followed by a proliferation burst 3 d into abstinence. However, in this area, there was a trend for reduced proliferation on days 7 and 21 of abstinence, and this was accompanied by significant suppression of DCX-IR, indicating a long-term suppression of forebrain neurogenesis. Finally, a decrease in the SOX2 stem cell marker was detected at days 7 and 21, suggesting long-term reduction of the SVZ stem cell pool. While suppression of hippocampal neurogenesis by alcohol dependence is transient, the suppression in the forebrain SVZ appears long-lasting

LONG-LASTING SUPPRESSION OF SUBVENTRICULAR ZONE NEUROGENESIS FOLLOWING A HISTORY OF ETHANOL DEPENDENCE

Exposure to repeated cycles of ethanol intoxication and withdrawal results in a well characterized persistent post-dependent increase in excessive voluntary ethanol consumption and behavioral sensitivity to stress. We have previously described some molecular neuroadaptations that contribute to these behavioral traits. Formation of new neurons in the adult brain, or adult neurogenesis, is related to stress responsiveness, and previous work has established that it is modulated by ethanol intoxication and withdrawal. Here, we asked whether adult neurogenesis is altered in the post-dependent state, in a manner that could contribute to the functional phenotype observed in this condition. To this end, we studied cell proliferation and neurogenesis in the subgranular zone of the dentate gyrus (SGZ) and in the subventricular zone lining the lateral ventricle (SVZ) in rats over a period of 3 weeks following a previously described 7 week intermittent ethanol vapor exposure to induce dependence, and compared to controls without a history of ethanol exposure. A single dose of 5-bromo-2-deoxyuridine (BrdU, 200 mg/kg, i.p.) was administered 4-5 h prior to euthanasia on day 0, 3, 7 and 21 post induction of dependence (abstinence days). Proliferating precursor cells incorporate the mitotic marker BrdU and were identified using immunohistochemistry in SVZ and SGZ. In agreement with prior work, ethanol exposure decreased density and number of proliferating cells by 70 % in both the SVZ (p<0.001) and SGZ (p<0.05), followed by a 2- fold rebound burst in proliferation on day 3 (p<0.001) of abstinence. In the SGZ, proliferation returned to normal levels within one week. However, the density of proliferating cells in the SVZ remained significantly decreased on day 7 (36%, p<0.01) and day 21 (35%, p<0.05) of abstinence. These changes were paralleled by decreased doublecortin expression, a neuronal marker expressed shortly after neuronal cell fate determination. Our data indicate a long-lasting suppression of neurogenesis in the SVZ of post-dependent rats, potentially leading to reduced neuronal turnover in the olfactory bulb and possibly also in prefrontal cortex circuitry. Although, the functional correlates of SVZ suppression are unknown, loss of olfactory discrimination is common in alcoholics and correlates with loss of executive function

A novel brain penetrant NPS receptor antagonist, NCGC00185684, blocks alcohol-induced ERK-phosphorylation in the central amygdala and decreases operant alcohol self-administration in rats.

The Neuropeptide S receptor, a Gs/Gq-coupled GPCR expressed in brain regions involved in mediating drug reward, has recently emerged as a candidate therapeutic target in addictive disorders. Here, we describe the in vitro and in vivo pharmacology of a novel, selective and brain penetrant NPSR antagonist with nanomolar affinity for the NPSR, NCGC00185684. In vitro, NCGC00185684 shows biased antagonist properties, and preferentially blocks ERK-phosphorylation over intracellular cAMP or calcium responses to NPS. In vivo, systemic NCGC00185684 blocks alcohol-induced ERK-phosphorylation in the rat central amygdala, a region involved in regulation of alcohol intake. NCGC00185684 also decreases operant alcohol self-administration, and lowers motivation for alcohol reward as measured using progressive ratio responding. These effects are behaviorally specific, in that they are observed at doses that do not influence locomotor activity or reinstatement responding following extinction. Together, these data provide an initial validation of the NPSR as a therapeutic target in alcoholism

Pituitary adenylate cyclase-activating polypeptide is a sympathoadrenal neurotransmitter involved in catecholamine regulation and glucohomeostasis

The adrenal gland is important for homeostatic responses to metabolic stress: hypoglycemia stimulates the splanchnic nerve, epinephrine is released from adrenomedullary chromaffin cells, and compensatory glucogenesis ensues. Acetylcholine is the primary neurotransmitter mediating catecholamine secretion from the adrenal medulla. Accumulating evidence suggests that a secretin-related neuropeptide also may function as a transmitter at the adrenomedullary synapse. Costaining with highly specific antibodies against the secretin-related neuropeptide pituitary adenylate cyclase-activating peptide (PACAP) and the vesicular acetylcholine transporter (VAChT) revealed that PACAP is found in nerve terminals at all mouse adrenomedullary cholinergic synapses. Mice with a targeted deletion of the PACAP gene had otherwise normal cholinergic innervation and morphology of the adrenal medulla, normal adrenal catecholamine and blood glucose levels, and an intact initial catecholamine secretory response to insulin-induced hypoglycemia. However, insulin-induced hypoglycemia was more profound and longer-lasting in PACAP knock-outs, and was associated with a dose-related lethality absent in wild-type mice. Failure of PACAP-deficient mice to adequately counterregulate plasma glucose levels could be accounted for by impaired long-term secretion of epinephrine, secondary to a lack of induction of tyrosine hydroxylase, normally occurring after insulin hypoglycemia in wild-type mice, and a consequent depletion of adrenomedullary epinephrine stores. Thus, PACAP is needed to couple epinephrine biosynthesis to secretion during metabolic stress. PACAP appears to function as an “emergency response” cotransmitter in the sympathoadrenal axis, where the primary secretory response is controlled by a classical neurotransmitter but sustained under paraphysiological conditions by a neuropeptide