Social isolation stress: role of neurosteroids in the action of ethanol on GABAAR

描述(申请人提供)：最近，有人提出，乙醇的某些效应可以通过增加大脑中神经活性类固醇的水平来调节，如3a，5a-THP，它具有在纳摩尔浓度增加GABAA受体功能的能力。乙醇诱导的神经活性类固醇浓度的增加似乎是由于刺激下丘脑-垂体-肾上腺(HPA)轴，至少部分是由于直接刺激脑神经类固醇生成。社交隔离是一种长期的轻度应激模式，已被证明与显著的行为变化有关，如实验动物的运动活动增加、焦虑、抑郁和攻击性。社会隔离导致大脑和血浆中神经活性类固醇浓度的降低，并伴随着对急性应激刺激的异常反应，以及由于急性给予乙醇而导致的神经类固醇生成效应的增加。我们打算使用C57BL/6J小鼠品系的社会隔离作为长期温和应激的模型，以进一步研究神经类固醇在乙醇对海马区和杏仁核GABAA受体功能的急性和慢性作用中的作用以及与应激的相互作用。在与社会隔离的小鼠中，我们将在以下实验条件下测量乙醇的影响：i)急性给药后；ii)通过蒸汽吸入慢性暴露后；iii)在自由选择的饮酒范例中，以确定这种条件是否会增加乙醇的消耗。脑组织中的神经类固醇水平将通过RIA进行评估。用核糖核酸酶保护法和免疫组织化学方法检测GABAA受体基因的表达。GABAA受体功能将通过常规的全细胞膜片钳记录在脑片上进行检测。这项研究如果成功，将有助于进一步了解神经类固醇作为酒精某些药理作用的内源性介质的作用，以及应激诱导的神经元可塑性适应性变化的分子机制以及与酒精消费的相互作用。鉴于许多应激以及生理病理情况，如经前综合征、抑郁和焦虑，可能与血浆和大脑神经类固醇浓度的显著波动有关，这项研究的结果将提供关于这些情况下易受酒精滥用影响的更多见解。

DESCRIPTION (provided by applicant): Recently, it has been proposed that certain effects of ethanol could be mediated by an increase in the brain levels of neuroactive steroids, such as 3a,5a-THP, which has the ability to increase at nanomolar concentrations the GABAA receptor function. Ethanol-induced increase in neuroactive steroid concentrations appear to result from stimulation of the hypothalamic-pituitary-adrenal (HPA) axis, and at least in part, from a direct stimulation of brain eurosteroidogenesis. Social isolation is a model of prolonged mild stress that has been shown to be associated to marked behavioral alterations, such as increased locomotor activity, anxiety, depression, and aggressiveness in laboratory animals. Social isolation results in a decrease in the brain and plasma concentrations of neuroactive steroids, and is accompanied by an abnormal response to acute stressful stimuli as well as by an increased neurosteroidogenic effect induced by the acute administration of ethanol. We intend to use social isolation in C57BL/6J mouse strain as a model of prolonged mild stress in which to investigate further the role of neurosteroids in the acute and chronic actions that ethanol exerts on the function of GABAA receptors in the hippocampus and amygdala and the interplay with stress. In socially isolated mice, we will measure the effects of ethanol in the following experimental condition: i) after acute administration; ii) after chronic exposure by vapor inhalation, and iii) in a free-choice drinking paradigm in order to establish if this condition can increase ethanol consuption. Neurosteroid levels in brain tissue will be assessed by RIA. GABAA receptor gene expression by RNase protection assay, and by immunohistochemistry. GABAA receptor function will be examined by conventional whole-cell patch clamp recording in brain slices. This project, if successful, by employing the social isolation stress will help to understand further the role of neurosteroids as endogenous mediators of certain pharmacological actions of ethanol as well as the molecular mechanisms underlying the neuronal plastic adaptive changes induced by stress and the interplay with ethanol consumption. Given that many stressful, as well as physiopathological, conditions such as PMS, depression and anxiety could be associated to marked fluctuations in plasma and brain concentrations of neurosteroids, the outcome of this study will provide additional insights about the vulnerability to ethanol abuse, characteristic of such conditions.