GABA-B Receptor Modulation of Calcium Currents

描述(由申请人提供)：该实验室的长期目标是加强我们对神经递质如何调节钙通道活动以及这种调节的功能后果的理解。γ-氨基丁酸(GABA)是哺乳动物中枢神经系统中的主要抑制性神经递质，它通过激活GABA-B受体来减弱N型钙电流。本实验室的一个独特发现是，在新生大鼠海马神经元中，GABA-B受体的激活促进了L电流的产生。了解这种促进作用的机制和功能意义将对药物成瘾、癫痫、失眠和焦虑等疾病的治疗产生重大影响，这些疾病通常使用与GABA能系统相互作用的化合物进行治疗。有待检验的中心假说是，GABA-B受体介导的L电流易化是通过激活GABAB受体介导的L钙电流易化的信号转导机制。具体目的#2是确定GAAB受体易化的L型钙通道的亚细胞定位。具体目标#3是确定GABAB受体的激活是否有助于在新生儿发育早期看到的钾偶联氯转运体表达的增加。该提案中概述的实验将使用全细胞和单通道记录、比率钙成像、免疫细胞化学和蛋白质的蛋白质印迹分析来实现该提案的目标。这项建议中概述的实验将提供关于L电流促进的信号转导机制的知识，并将通过确定出生后头两周大鼠海马区氯转运体表达的亚细胞位置以及上调表达的作用来开始研究这一效应的功能意义。更好地了解GABA-B受体的功能可能会允许对GABA能系统进行更微妙的操作，从而以更少的副作用更好地设计药物。

DESCRIPTION (provided by applicant): The long range goal of the laboratory is to enhance our understanding of how neurotransmitters modulate calcium channel activity and the functional consequences of this modulation. The main inhibitory neurotransmitter in the mammalian central nervous system, gamma-aminobutyric acid (GABA) is known to attenuate N-type calcium currents by activation of GABA-B receptors. A unique finding in our laboratory is that L-type current is facilitated in response to GABA-B receptor activation in the neonatal neurons of the rat hippocampus. Understanding the mechanisms and functional significance of this facilitation will have significant consequences for the treatment of diseases such as drug addiction, epilepsy, insomnia and anxiety that are routinely treated with compounds interacting with the GABAergic system. The central hypothesis to be tested is that GABA-B receptor mediated facilitation of L-type current in the superior region of the hippocampus is medfy the signal transduction mechanism of the facilitation of L-type calcium current by activation of GABAB receptors. Specific aim #2 is to determine the specific subcellular location of the L-type calcium channels facilitated by GABAB receptors. Specific aim #3 is to determine whether or not activation of GABAB receptors contributes to the increase in potassium coupled chloride transporter expression seen early in neonatal development. The experiments outlined in this proposal will use whole cell and single channel recording, ratiometric calcium imaging, immunocytochemistry and Western blot analysis of proteins to accomplish the aims of the proposal. The experiments outlined in this proposal will provide knowledge about the signal transduction mechanism underlying the facilitation of L-type current and will begin to investigate the functional significance of this effect by identifying the subcellular location as well as the role in up-regulation of chloride transporter expression in the first two postnatal weeks in the rat hippocampus. A better understanding of the GABA-B receptor function may allow more subtle manipulation of the GABAergic system allowing for better design of pharmaceuticals with fewer side effects.