Acute Corticosteriod Actions in the Hypothalamus

描述（由申请人提供）：应激与下丘脑-垂体-肾上腺（HPA）轴激活和循环肾上腺皮质类固醇水平升高相关。糖皮质激素反馈到下丘脑，不仅抑制促肾上腺皮质激素释放激素（CRH）的分泌和HPA的激活，而且还抑制许多其他下丘脑神经内分泌系统。糖皮质激素对下丘脑室旁核（PVN）神经元的负反馈调节分为两个阶段：CRH释放的急性抑制和CRH和加压素合成的缓慢下调。迄今为止，尚不清楚糖皮质激素在大脑中的何处发挥其对下丘脑神经分泌的负反馈调节，以及这种反馈的细胞机制是什么。这些问题对于治疗广泛的情感障碍具有深远的意义，包括影响大量人群的压力，抑郁和饮食失调。本建议的总体目的是确定是否急性负性糖皮质激素调节PVN神经内分泌系统直接发生在PVN的分泌糖皮质激素的神经元，并表征这种调节的细胞机制。我们有初步的证据表明，在PVN膜受体激活介导的快速抑制性糖皮质激素的作用和释放的逆行内源性大麻素信使，抑制兴奋性和促进抑制性输入PVN神经元。基于这些发现，我们拟在急性期大鼠下丘脑脑片上进行全细胞膜片钳记录，以验证以下具体假设：1。糖皮质激素通过刺激内源性大麻素介导的谷氨酸释放抑制和GABA释放促进来直接抑制PVN神经元; 2.糖皮质激素通过激活突触后G蛋白偶联受体和脂质信使信号级联反应引起PVN神经元的逆行内源性大麻素释放; 3.内源性大麻素介导的PVN中谷氨酸和GABA释放的变化由突触前、G蛋白和蛋白激酶依赖性信号传导机制介导。这些研究将首次揭示下丘脑中糖皮质激素快速作用的部位和生理机制。下丘脑中的快速糖皮质激素反馈在生物体对应激的整体反应中起着关键作用，并且了解下丘脑中糖皮质激素作用的机制将为治疗HPA相关病理提供重要的细胞靶点。此外，糖皮质激素-内源性大麻素的联系为下丘脑功能和大麻素之间的相互作用开辟了有趣的可能性。

DESCRIPTION (provided by applicant): Stress is associated with activation of the hypothalamic-pituitary-adrenal (HPA) axis and increased levels of circulating adrenal corticosteroids. Glucocorticoids feed back onto the hypothalamus to inhibit not only corticotropin releasing hormone (CRH) secretion and HPA activation, but also many other hypothalamic neuroendocrine systems. The negative feedback regulation by glucocorticoids occurs in two stages: an acute inhibition of the release of CRH, and a slower down-regulation of CRH and vasopressin synthesis in neurons of the hypothalamic paraventricular nucleus (PVN). To date, it is not known where in the brain glucocorticoids exert their negative feedback regulation of hypothalamic neurosecretion, and what the cellular mechanisms of this feedback are. These questions have profound significance for the treatment of widespread affective disorders, including stress, depression, and eating disorders, that impact large numbers of people. The overall purpose of this proposal is to determine whether acute negative glucocorticoid regulation of PVN neuroendocrine systems occurs directly at the hormone-secreting neurons in the PVN, and to characterize the cellular mechanisms of this regulation. We have preliminary evidence for rapid inhibitory glucocorticoid effects in the PVN mediated by membrane receptor activation and the release of a retrograde endocannabinoid messenger that suppresses excitatory and facilitates inhibitory inputs to PVN neurons. Based on these findings, we propose to conduct whole-cell patch-clamp recordings in acute rat hypothalamic slices to test the following specific hypotheses: 1. glucocorticoids inhibit PVN neurons directly by stimulating an endocannabinoid-mediated suppression of glutamate release and facilitation of GABA release; 2. glucocorticoids elicit retrograde endocannabinoid release from PVN neurons by activation of a postsynaptic G protein-coupled receptor and lipid messenger signaling cascade; 3. the endocannabinoid-mediated changes in glutamate and GABA release in the PVN are mediated by presynaptic, G protein- and protein kinase-dependent signaling mechanisms. These studies will reveal for the first time the site and physiological mechanisms of fast glucocorticoid actions in the hypothalamus. Fast glucocorticoid feedback in the hypothalamus plays a critical role in the organism's holistic response to stress, and understanding the mechanisms of glucocorticoid actions in the hypothalamus will provide important cellular targets for the treatment of HPA-related pathologies. Furthermore, the glucocorticoid-endocannabinoid link opens interesting possibilities for interactions between hypothalamic function and the cannabinoids.