MOLECULAR REGULATION OF POSTSYNAPTIC GABA RESPONSES

GABAA介导的突触抑制在许多正常神经元中起重要作用。 在中枢神经系统的生理过程，似乎是至关重要的 癫痫的生理学。 癫痫活动的发展， 癫痫发作在致痫区域，以及癫痫发作蔓延到 正常的大脑都是由于，或与，减少 抑制功效 调节GABAA介导抑制的因子 在突触后受体的水平上，只有部分了解， 作为GABA反应基础的Cl通道仅部分 表征了 我们以前的工作一直致力于表征GABAA介导的 抑制在培养的新皮层和海马神经元，在细胞 在分子水平上，采用细胞内、全细胞膜片钳和单细胞膜片钳技术， 频道录制技术 我们将继续进行这些研究， 最初是关于脱敏的分子机制， GABAA受体在细胞和单个核细胞上的再敏化 渠道水平。 我们将确定这些过程是否与变化有关 在Cai或cAMP中，激活或抑制蛋白激酶， 磷酸酶，或调节G蛋白或磷酸肌醇途径。 我们 将描述GABA激活的Cl通道的特性，包括 主要导电状态的大小，其他子状态的存在， 通道打开和关闭的动力学，包括打开的趋势， 脉冲串以及对信道的其他生理影响。 我们还将 确定灵敏度降低是否是由于单个通道的变化 电导，开口概率或突发与单个 开放，开放时间的变化或一种Cl亚型的失活 通道（正如我们最近证明的， 使君子酸受体） 通过GABA发挥作用的几种重要药物的作用机制 受体复合物，包括苯二氮卓类，巴比妥类， β-咔啉和孕酮代谢物将在 通道水平，我们将确定是否与 皮层神经元内GABA对GABA有直接的调节作用 受体和Cl通道。 我们还将确定是否激活 谷氨酸受体亚型影响GABA反应， 激活影响由兴奋性 神经递质（NT）作用。 最后，如果GABA反应受到第二信使途径的影响， 将确定这些影响如何可能介导的其他NT， 这些系统，尤其是NE、DA、SOM、VIP和CCK。 希望通过了解GABAA介导的 在分子水平上的抑制，我们将能够设计新的策略， 用于防止抑制的丧失，所述抑制似乎促进 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.