Homeostatic Regulation of Supraoptic Neurons: Role of BDNF

描述（由申请人提供）：这些研究的目的是确定脑源性神经营养因子（BDNF）及其受体TrkB如何影响加压素释放以应对进行性生理挑战，即缺水。我们的数据表明，BDNF可能通过磷酸化NR2B和增加氯转运体KCC2的表达来促进缺水期间谷氨酸和GABA的信号传导。NR2B磷酸化的增加会增加NMDA受体的激活，增强抗利尿激素的释放，而KCC2活性的增加会增加GABA的抑制作用，这代表了在缺水时突触对兴奋增加的稳态补偿。特异性目的1：在缺水诱导的持续抗利尿激素释放过程中，确定神经垂体BDNF-TrkB信号和通过NR2B磷酸化增强谷氨酸的作用。假设：与缺水相关的TrkB磷酸化导致谷氨酸活性增强，这是由于NR2B NMDA受体亚基通过Fyn激酶磷酸化，Fyn激酶是Src激酶家族的一员，在跨国公司中参与NMDA介导的可塑性。具体目的2：验证神经垂体BDNF-TrkB信号传导在缺水期间增强GABA抑制作用的假设。假设：BDNF-TrkB信号在缺水过程中增加KCC2表达，通过Src激酶增强跨国公司GABA的抑制作用，而不激活磷脂酶C γ。方法：这些实验将首次明确BDNF-TrkB信号在AVP持续释放的稳态调节中的作用。将采用综合方法，包括体外和体内电生理实验，TrkB和Src激酶拮抗剂局部应用于SON的全动物实验，以及大鼠水平衡和AVP释放的功能研究。益处：这些实验将解决我们对神经垂体功能生理调节的理解中的一个现有空白。这些实验的发现可能潜在地改变临床研究和概念化抗利尿激素不适当释放的方式。

DESCRIPTION (provided by applicant): The goal of these studies is to determine how Brain derived neurotrophic factor (BDNF) and its receptor TrkB influence vasopressin release to a progressive physiological challenge, water deprivation. Our data suggest that BDNF may facilitate both glutamate and GABA signaling during water deprivation by causing phosphorylation NR2B and increasing the expression of the chloride transporter KCC2. Increased NR2B phosphorylation would increase NMDA receptor activation enhancing vasopressin release while increased KCC2 activity could increase the inhibitory effects of GABA representing a homeostatic synaptic compensation to increased excitation during water deprivation. Specific Aim 1: to determine the role of neurohypophysial BDNF-TrkB signaling and enhanced glutamate action through NR2B phosphorylation during sustained vasopressin release induced by water deprivation. Hypothesis: Phosphorylation of TrkB associated with water deprivation leads to enhanced glutamate activity due to phosphorylation of NR2B NMDA receptor subunits through Fyn kinase, a member of the Src kinase family contributing to NMDA mediated plasticity in MNCs Specific Aim 2: to test the hypothesis that neurohypophysial BDNF-TrkB signaling enhances the inhibitory effects of GABA during water deprivation. Hypothesis: BDNF-TrkB signaling during water deprivation increases KCC2 expression enhancing the inhibitory effects of GABA in MNCs via Src kinase and without the activation of Phospholipase C gamma. Methods: These experiments will for the first time define the roles of BDNF-TrkB signaling in the homeostatic regulation of sustained AVP release. An integrative approach will be employed that includes in vitro and in vivo electrophysiological experiments, whole animal experiments in which TrkB and Src kinase antagonists will be locally applied to the SON, and functional studies of water balance and AVP release in the rat. Benefit: These experiments will address an existing gap in our understanding of the physiological regulation of neurohypophyseal function. The findings of these experiments could potentially alter the way that inappropriate vasopressin release is studied and conceptualized clinically.