MOLECULAR REGULATION OF POSTSYNAPTIC GABA RESPONSES

GABAA介导的突触抑制在许多正常人中起着重要作用 在中枢神经系统中的生理过程，似乎是至关重要的 在癫痫的生理学方面。癫痫活动的发展， 癫痫在致痫区域的发作，以及癫痫的蔓延到 正常的大脑都是由于或与脑功能减退有关 抑制效果。调节GABAA介导的抑制作用的因素 在突触后受体的水平上，人们只了解了一部分 作为GABA反应基础的氯通道只是部分 特色化的。 我们之前的工作一直致力于表征GABAA介导的 培养的新皮质和海马神经元对细胞的抑制 和分子水平，采用细胞内、全细胞膜片钳和单细胞 频道录制技术。我们将继续这些研究，重点是 初步探讨脱敏和脱敏的分子机制 GABAA受体在细胞和单个细胞上的再增敏 频道级别。我们将确定这些过程是否与变化相关 在CaI或cAMP中，激活或抑制蛋白激酶或 磷酸酶，或G蛋白或磷酸肌醇途径的调节。我们 将描述GABA激活的氯通道的特性，包括 主导电态的大小、其他子态的存在、 渠道打开和关闭的动力学，包括打开的趋势 突发，以及对通道的其他生理影响。我们还将 确定脱敏是否由单通道改变引起 电导，开路概率或脉冲串相对于单个电导的变化 打开，打开时间的改变或一种亚型氯离子的失活 渠道(正如我们最近演示的脱敏 Quisqualate受体。) 几种通过GABA发挥作用的重要药物的作用机制 受体复合体，包括苯二氮卓类，巴比妥类， β-卡波林和孕酮代谢物将在 通道水平，我们将确定是否与 皮质神经元中的GABA对GABA具有直接的调制作用 受体和氯离子通道。我们还将确定是否激活 谷氨酸受体亚型影响GABA反应以及GABA是否 兴奋影响兴奋性脑内钙离子浓度的变化 神经递质(NT)作用。 最后，如果GABA反应受到第二信使通路的影响，我们 将确定这些影响可能如何由其他影响 这些系统，特别是NE、DA、SOM、VIP和CCK。 希望通过了解GABAA介导的调控 在分子水平上的抑制我们将能够设计出新的策略 为了防止抑制的丧失，这似乎促进了 癫痫的发展和蔓延。

GABAA-mediated synaptic inhibition plays an important role in many normal physiological processes in the CNS and appears to be critically important in the physiology of epilepsy. The development of epileptic activity, the onset of seizures in an epileptogenic area, and the spread of seizures to normal brain are all either due to, or are associated with, a decrease in inhibitory efficacy. The factors which regulae GABAA mediated inhibition at the level of the postsynaptic receptor are only partially understood and the Cl channels which underlie the GABA response are only partially characterized. Our previous work has been devoted to characterizing GABAA-mediated inhibition in cultured neocortical and hippocampal neurons, at the cellular and molecular level, using intracellular, whole cell patch clamp and single channel recording techniques. We will continue these studies, focusing initially on the molecular mechanisms responsible for desensitization and resensitization of the GABAA receptor at both the cellular and single channel level. We will determine if these processes are related to changes in Cai or cAMP, activation or inhibition of protein kinases or phosphatases, or modulation of G proteins or phosphoinositol pathways. We will describe the properties of the GABA-activated Cl channel, including the size of the main conducting state, the presence of other substates, the kinetics of channel openings and closing, including tendency to open in bursts, and other physiological influences on the channel. We will also determine if desensitization is due to a change in single channel conductance, a change in probability of openings or in burst versus single opening, a change in open times or inactivation of one subtype of Cl channel (as we have recently demonstrated for desensitization at the quisqualate receptor.) The mechanisms of action of several important drugs which work via the GABA receptor complex, including the benzodiazepines, barbiturates, beta-carbolines, and progesterone metabolites will be analyzed at the channel level and we will determine if neuropeptides which co-exist with GABA in cortical neurons have direct modulatory effects on the GABA receptor and Cl channel. We will also determine whether activation of glutamate receptor subtypes affects GABA responses and whether GABA activation influences the changes in CAi induced by excitatory neurotransmitter (NT) action. Finally, if GABA responses are affected by second messenger pathways, we will determine how these effects may be mediated by other NTs which affect these systems, especially NE, DA, SOM, VIP and CCK. It is hoped that by understanding the regulation of GABAA-mediated inhibition at the molecular level we will be able to devise new strategies for preventing the loss of inhibition which appears to promote the development and spread of seizures.