Cellular mechanisms of HPA axis neuroadaptations in alcohol dependence

描述（由申请人提供）：酒精中毒是一种慢性复发性障碍，其特征是强迫性酒精寻求和对酒精摄入失去控制。已知酒精中毒与下丘脑垂体肾上腺（HPA）轴和促肾上腺皮质激素释放激素（CRH）信号的持续失调有关，导致对压力的不适当反应，从而增加戒断性酗酒者的复发易感性。然而，细胞和分子机制负责钝化HPA轴对压力的戒酒者尚未发现。在大鼠中，急性约束应激诱导下丘脑室旁核旁细胞神经分泌细胞（pnc）中n -甲基-d -天冬氨酸受体（NMDAR）功能的crh依赖性抑制，这允许在兴奋性输入的高频刺激（HFS）爆发后揭示联合短期突触增强（STP）。这代表了应激诱导下丘脑轴神经适应性反应的细胞机制。慢性间歇乙醇（CIE）暴露诱导的酒精依赖大鼠模型的初步结果表明，在没有急性应激的情况下，CIE大鼠的pnc可以诱导STP。相比之下，急性应激CIE大鼠的pnc中STP受损。我们还证明了突触后NMDAR功能的持久增强与NMDAR GluN2B亚基在CIE大鼠pnc中的表达增加有关。总之，初步结果强烈表明，CIE暴露改变了pnc中基础和应激诱导的突触可塑性，这可能是酒精依赖大鼠中HPA轴对应激的特征性激素反应减弱的原因。因此，该提议的主要假设是，cie诱导的STP损伤是由PVN中NMDAR功能和CRH信号的长期改变介导的。我们还假设，恢复这种应力诱导的可塑性将恢复下丘脑轴对压力源的反应性。为了验证这些假设，我们将结合行为学、电生理学、生物化学和药理学技术来确定：1)慢性EtOH暴露后，NMDAR信号改变在pnc中谷氨酸突触应力诱导可塑性中的作用，以及2)慢性EtOH暴露在长时间戒断期间改变PVN pnc中CRH信号的机制。这些研究将有助于揭示酒精依赖中HPA轴对压力反应失调背后的细胞机制，这将有助于发现压力诱导的强迫性酒精寻求的新有效疗法。

DESCRIPTION (provided by applicant): Alcoholism is a chronic relapsing disorder characterized by compulsive ethanol-seeking and loss of control over alcohol intake. Alcoholism is known to be associated with a persistent dysregulation of the hypothalamic pituitary adrenal (HPA) axis and corticotropin-releasing hormone (CRH) signaling that leads to inappropriate responses to stress, thereby increasing relapse susceptibility in abstinent alcoholics. However, the cellular and molecular mechanisms responsible for the blunted HPA axis responses to stress in abstinent alcoholics have yet to be uncovered. In rats, acute restraint stress induces a CRH-dependent depression of N-methyl-D- aspartate receptor (NMDAR) function in parvocellular neurosecretory cells (PNCs) of the paraventricular nucleus of the hypothalamus (PVN) which allows for the unmasking of associative short-term synaptic potentiation (STP) following a burst of high-frequency stimulation (HFS) of excitatory inputs. This represents a cellular mechanism by which stress induces neuroadaptive responses of the HPA axis. Preliminary results in a rat model of alcohol dependence induced by chronic intermittent ethanol (CIE) exposure show that STP can be induced in PNCs of CIE rats without acute stress. By contrast, STP is impaired in PNCs from acutely stressed CIE rats. We also demonstrated long-lasting potentiation of postsynaptic NMDAR function associated with increased expression of the GluN2B subunit of NMDARs in PNCs of CIE rats. Altogether, preliminary results strongly suggest that CIE exposure modifies both basal and stress-induced synaptic plasticity in PNCs, which could be responsible for the characteristically blunted hormonal response of the HPA axis to stress in alcohol- dependent rats. Thus, the main hypothesis of this proposal is that CIE-induced impairment of STP is mediated by the long-lasting alterations in both NMDAR function and CRH signaling in the PVN. We also hypothesize that restoring this stress-induced plasticity will restore the HPA axis responsiveness to stressors. To test these hypotheses we will use a combination of behavioral, electrophysiological, biochemical and pharmacological techniques to determine: 1) the role of altered NMDAR signaling in stress-induced plasticity at glutamatergic synapses in PNCs after withdrawal from chronic EtOH exposure, and 2) the mechanisms by which chronic EtOH exposure alters CRH signaling in PNCs of the PVN during protracted withdrawal. These studies will help uncover the cellular mechanisms behind the dysregulation of the HPA axis response to stress in alcohol dependence, which will be useful in the discovery of new effective therapies for stress-induced compulsive alcohol seeking.