Neurobiological studies of gammahydroxybutyrate

描述(申请人提供)：伽马羟丁酸酯(GHB)是中间代谢的产物，对中枢神经系统(CNS)的活动有深远的影响，特别是对意识。由于其催眠作用，GHB已成为一种滥用药物，矛盾的是，它还成为治疗睡眠障碍发作性睡病的临床有效疗法。嗜睡症是一种与快速眼动(REM)睡眠相关的疾病，大约每1000名美国人中就有一人受到影响，其特征是白天过度嗜睡(EDS)、猝倒(由情绪刺激引发的肌肉张力突然丧失)和一系列其他症状。Xyrem是GHB的钠盐，已被美国食品和药物管理局批准用于治疗发作性睡病和EDS症状。GHB促进脑电中的慢波活动(SWA)和慢波睡眠(SWS)，从而巩固夜间睡眠，从而提高第二天的警觉性。尽管GHB具有临床应用价值，但其作用机制仍存在争议，有证据表明它既通过GABA-B受体发挥作用，也通过中枢神经系统中特定的GHB结合部位发挥作用。该项目的具体目标是确定GHB诱导的SWA的神经底物，并了解GHB治疗发作性睡病/猝倒的潜在机制(S)。为了实现这些目标，我们将利用发作性睡病/猝倒的小鼠模型，在这种模型中，下丘脑泌素(Hcrt)神经元在出生后退化，就像人类发作性睡病患者一样。我们将利用这些hcrt/ataxin-3小鼠来跟进我们的初步结果，这些结果表明GHB可以像在人类一样减少卡他样症状，并测试这些治疗效果是通过GABA-B受体介导的假设。我们将进行功能神经解剖学研究，以检验GHB对hcrt/ataxin-3小鼠行为状态调节区的不同影响这一假设。根据我们的初步结果，在GHB诱导蓝斑(LC)Fos表达的基础上，我们将使用神经毒素DSP-4来损害去甲肾上腺素能细胞，以验证完整的LC是GHB治疗效果所必需的假说。我们还将进行细胞电生理研究，以确定LC或视前腹侧区(VLPO)神经元的固有特性是否受到急性或慢性GHB暴露的影响。最后，我们将评估GHB的疗效是否与脑基因表达的变化有关。上述研究的结果将加强我们对GHB治疗活性的神经生物学的理解，也可能为理解猝倒和EEG SWA的细胞和分子机制提供帮助。与公共卫生相关的发作性睡病患者，一种以白天过度嗜睡和相关症状为特征的睡眠障碍，大脑中的下丘脑神经元变性已被观察到。羟丁酸伽玛(GHB)是一种治疗睡眠障碍发作性睡病的有效药物，但其作用机制尚不清楚。我们将利用发作性睡病的小鼠模型，其中Hcrt神经元在出生后退化，就像它们在人类发作性睡病中所做的那样，以了解GHB如何在人类发作性睡病中有益。

DESCRIPTION (provided by applicant): Gammahydroxybutyrate (GHB), a product of intermediary metabolism, has profound effects on the activity of the central nervous system (CNS), particularly on consciousness. Because of its soporific effects, GHB has become both a drug of abuse and, paradoxically, a clinically useful therapeutic for treatment of the sleep disorder narcolepsy. Narcolepsy, a Rapid Eye Movement (REM) sleep-related disorder that afflicts approximately 1 in 1000 Americans, is characterized by excessive daytime sleepiness (EDS), cataplexy (a sudden loss of muscle tone triggered by emotional stimulation), and a cluster of other symptoms. Xyrem, the sodium salt of GHB, has been approved by the U.S. Food and Drug Administration for the treatment of both the cataplexy and EDS symptoms of narcolepsy. GHB facilitates slow wave activity (SWA) in the EEG and slow wave sleep (SWS), thereby consolidating nocturnal sleep and resulting in increased alertness on the subsequent day. Despite its clinical utility, the mechanism of action of GHB remains controversial with evidence for action both through GABA-B receptors and through specific GHB binding sites in the CNS. The specific goals of this project are to identify the neural substrates of GHB-induced SWA and understand the mechanism(s) underlying the therapeutic effects of GHB on narcolepsy/cataplexy. To achieve these goals, we will exploit a mouse model of narcolepsy/cataplexy in which the hypocretin (Hcrt) neurons degenerate postnatally as they do in human narcoleptics. We will follow up on our preliminary results using these hcrt/ataxin-3 mice which indicate that GHB can reduce cataplexy-like symptoms as it does in humans and test the hypothesis that these therapeutic effects are mediated through the GABA-B receptor. We will conduct functional neuroanatomical studies to test the hypothesis that GHB differentially affects behavioral state regulatory regions in hcrt/ataxin-3 mice. Based on our preliminary results in which GHB induces Fos expression in the locus coeruleus (LC), we will use the neurotoxin DSP-4 to lesion noradrenergic cells to test the hypothesis that an intact LC is necessary for the therapeutic effect of GHB. We will also conduct cellular electrophysiological studies to determine whether the intrinsic properties of the neurons in the LC or the ventrolateral preoptic area (VLPO) are affected by acute or chronic exposure to GHB. Lastly, we will evaluate whether the therapeutic efficacy of GHB is associated with brain gene expression changes. The results of the studies proposed above will enhance our understanding of the neurobiology that underlies the therapeutic activity of GHB and may also provide insights into the cellular and molecular mechanisms that underlie cataplexy and EEG SWA. PUBLIC HEALTH RELEVANCE In patients with narcolepsy, a sleep disorder characterized by excessive daytime sleepiness and related symptoms, degeneration of hypocretin (Hcrt) neurons in the brain has been observed. Gammahydroxybutyrate (GHB) is a clinically useful therapeutic for treatment of the sleep disorder narcolepsy but the mechanism of action is unknown. We will exploit a mouse model of narcolepsy in which the Hcrt neurons degenerate postnatally as they do in human narcoleptics to understand how GHB is beneficial in human narcolepsy.