Homeostatic Regulation of Supraoptic Neurons: Role of BDNF

描述(申请人提供)：这些研究的目标是确定脑源性神经营养因子(BDNF)及其受体TrkB如何影响血管加压素的释放，以应对进行性的生理挑战，即缺水。我们的数据表明，BDNF可能通过引起NR2B的磷酸化和增加氯转运体KCC2的表达来促进水分胁迫下谷氨酸和GABA的信号转导。增加NR2B的磷酸化可以增加NMDA受体的激活，促进加压素的释放，而增加KCC2的活性可以增加GABA的抑制作用，这是一种对水分胁迫下兴奋增加的动态平衡突触补偿。具体目的1：探讨在缺水诱导的加压素释放过程中，神经垂体BDNF-TrkB信号通路和NR2B磷酸化增强谷氨酸作用。假说：与缺水相关的TrkB的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激酶被磷酸化，Fyn激酶是参与NMDA介导的单核细胞可塑性的Src激酶家族的成员。假说：缺水时BDNF-TrkB信号增加KCC2的表达，增强GABA对MNC的抑制作用，这种抑制作用是通过Src激酶实现的，而不是通过激活磷脂酶C-γ。方法：这些实验将首次确定BDNF-TrkB信号在AVP持续释放的动态平衡调节中的作用。将采用一种综合的方法，包括体外和体内电生理实验，局部应用TrkB和Src激酶拮抗剂的全动物实验，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在了解神经垂体功能的生理调节方面存在的一个空白。这些实验的发现可能会改变不适当的加压素释放的临床研究和概念化的方式。

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.