Neurosteroid Modulation of Ethanol Withdrawal Severity

描述(申请人提供)：神经类固醇别孕酮(ALLO)是一种有效的GABAA受体的正向调节剂，有证据表明GABA能神经类固醇是GABAA受体和乙醇(EtoH)选择性效应的内源性调节剂。本提案建立在当前资助期间在选择性繁殖的易戒断(WSP)和耐受(WSR)雄性小鼠中产生的结果的基础上。WSP小鼠在乙醇戒断期间内源性Allo水平持续下降，同时对Allo的抗惊厥作用耐受，这一发现与乙醇戒断期间WSP与WSR系相比更强的神经兴奋性是一致的。Allo对乙醇戒断严重程度的调节作用的选定品系差异可能反映了GABAA受体上Allo局部浓度的变化与乙醇戒断期间伴随的GABAA受体对Allo敏感性的变化之间的平衡。因此，本研究的目标是确定WSP小鼠在乙醇戒断期间对Allo耐受的机制和作用部位(S)(目标3)，局部内源性Allo水平变化(Aim 2)和GABAA受体亚单位表达变化(Aim 4)对WSP和WSR小鼠在乙醇戒断严重期间对Allo敏感性的线差异的相对贡献，以及WSP和WSR小鼠在乙醇戒断过程中生物合成酶5a-还原酶(Srd5a1)的解剖定位和调节(目标1)。结果的模式将提供重要的信息，关于特定脑区的GABAA受体的激活是否足以改变无水乙醇戒断的严重程度或在无水乙醇戒断期间对Allo的敏感性，以及特定脑区局部Allo浓度对无水乙醇戒断严重程度的关键参与。这一多学科的方法将进一步检验这一假说，即内源性Allo水平的降低改变了GABAA能张力，同时GABAA受体敏感性的降低导致WSP小鼠戒断严重程度的增加。这项研究的长期目标是了解戒断严重程度增加的遗传倾向背后的机制。这些信息将有助于我们了解酒精戒断的机制，并将有助于制定治疗酒精依赖的新策略。

DESCRIPTION (provided by applicant): The neurosteroid allopregnanolone (ALLO) is a potent positive modulator of GABAA receptors, and evidence suggests that GABAergic neurosteroids are endogenous modulators of GABAA receptors and of selective effects of ethanol (EtOH). The present proposal builds on results generated in the current period of funding in the selectively bred Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) male mice. The finding that WSP mice had a persistent decrease in endogenous ALLO levels during EtOH withdrawal, in conjunction with tolerance to ALLO's anticonvulsant effect, is consistent with greater neural excitability in the WSP vs. WSR line during EtOH withdrawal. The selected line differences in the modulatory effect of ALLO on EtOH withdrawal severity likely reflects a balance between alterations in local concentration of ALLO at GABAA receptors and the concomitant change in GABAA receptor sensitivity to ALLO during EtOH withdrawal. Thus, the goals of the proposed studies are to determine the mechanism and site(s) of action underlying the tolerance to ALLO during EtOH withdrawal in WSP mice (Aim 3), the relative contribution of altered local endogenous ALLO levels (Aim 2) and altered expression of GABAA receptor subunits (Aim 4) to the line difference in ALLO sensitivity during EtOH withdrawal severity in WSP and WSR mice, and the anatomical localization and regulation of the biosynthetic enzyme 5a-reductase (Srd5a1) during EtOH withdrawal in WSP and WSR mice (Aim 1). The pattern of the results will provide essential information on whether activation of GABAA receptors in particular brain regions will be sufficient to alter EtOH withdrawal severity or sensitivity to ALLO during EtOH withdrawal as well as the critical involvement of local ALLO concentration in a specific brain region on EtOH withdrawal severity. This multidisciplinary approach will further test the hypothesis that a decrease in endogenous ALLO levels, which alters GABAergic tone, in conjunction with a decrease in GABAA receptor sensitivity, contribute to the increased withdrawal severity in WSP mice. The long-term goal of this research is to understand mechanisms underlying a genetic predisposition for increased withdrawal severity. This information will aid in our understanding of the mechanisms underlying alcohol withdrawal and will help in the development of new strategies for the treatment of alcohol dependence.