SYNAPTIC INTEGRATION BY HIPPOCAMPAL NEURONS

描述：(申请人摘要) 这个项目试图更清楚地理解突触后的因素 它们塑造了快速的IPSCs和EPSCs以及突触 输入整合在海马神经元的树突上。 一组实验将确定GABAA和AMPA受体的影响 对突触传递的脱敏。对人体的生理影响 脱敏作用在很大程度上是通过从 离体外翻膜受体的动力学研究结果 帕奇斯。隐含的假设是突触的动力学特性 受体可以被O-O斑块中的受体忠实地模拟。 然而，这一假设尚未对AMPA和GABAA进行直接测试 感受器。事实上，我们的初步数据表明，补丁的过程 分离改变AMPA和GABAA的脱敏特性 受体，对后一种受体的影响尤其显著。 第二组实验将确定突触 在时间和空间上分离的输入由树枝结合在一起，树枝是一种基本的 神经生物学中仍然知之甚少的问题。我们的初步数据 表明树枝晶的总和不能用单一的 过程与肌肉终板的经典研究中所展示的相似。 相反，我们假设求和很容易在不同的模式之间切换 (例如线性、次线性和超线性)。我们建议这样的模式 切换是树枝的时间和空间总和的一个定义特征 中枢神经系统中的神经元。 分离培养和器官切片培养中的海马神经元 将会被研究。用膜片钳记录突触后反应 技巧。谷氨酸和GABA将应用于树突状受体的原位研究 利用我们最近获得的一种快速聚焦光解的新方法 发展起来的。这项创新使我们能够克服主要的技术问题 使这些根本问题以前无法触及的问题。

DESCRIPTION: (Applicant's Abstract) This project seeks a clearer understanding of both the postsynaptic factors that shape fast IPSCs and EPSCs as well as the mechanism by which synaptic inputs are integrated on the dendrites of hippocampal neurons. One set of experiments will determine the impact of GABAA and AMPA receptor desensitization on synaptic transmission. The physiological impact of desensitization has been inferred, in large part, by extrapolation from the results of kinetic studies of receptors in excised outside-out (O-O) membrane patches. The implicit assumption is that the kinetic properties of synaptic receptors can be faithfully modeled by those of receptors in O-O patches. However, this assumption has yet to be directly tested for AMPA and GABAA receptors. Indeed, our preliminary data suggest that the process of patch isolation alters the desensitization properties of both AMPA and GABAA receptors, with the effect on the latter receptors being especially marked. A second set of experiments will determine the mechanism by which synaptic inputs separated in time and space are combined by the dendrite, a fundamental issue in neurobiology that remains poorly understood. Our preliminary data suggest that summation on dendrites cannot be adequately described by a single process similar to that demonstrated in classic studies of the muscle endplate. Instead, we postulate that summation readily switches between different modes (such as linear, sublinear, and supralinear). We propose that such mode switching is a defining feature of temporal and spatial summation by dendrites of neurons in the central nervous system. Hippocampal neurons in dissociated cultures and in organotypic slice cultures will be studied. Postsynaptic responses will be recorded with patch clamp techniques. Glutamate and GABA will be applied to dendritic receptors in situ with the use of a novel method of rapid focal photolysis that we have recently developed. This innovation has enabled us to overcome the major technical problems that had rendered these fundamental issues previously inaccessible.