SYNAPTIC INTEGRATION BY HIPPOCAMPAL NEURONS

描述：（申请人摘要） 本项目旨在更清楚地了解突触后因素 形成快速IPSC和EPSC的机制，以及突触 输入被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， 突触传递的脱敏作用。的生理影响 脱敏已推断，在很大程度上，通过外推从 切除的外向（O-O）膜中受体的动力学研究结果 补丁.隐含的假设是，突触的动力学特性 受体可以忠实地由O-O斑中的受体模拟。 然而，这一假设尚未直接测试AMPA和GABAA 受体。事实上，我们的初步数据表明， 隔离改变AMPA和GABAA的脱敏特性 受体，对后者受体的影响特别明显。 第二组实验将确定突触 在时间和空间上分离的输入由树突组合， 神经生物学中仍然知之甚少的问题。我们的初步数据 表明树突上总和不能用单一的 这一过程类似于肌肉终板的经典研究。 相反，我们假设求和容易在不同模式之间切换 (such线性、次线性和超线性）。我们建议，这种模式 开关是树突的时间和空间叠加的定义特征 中枢神经系统中的神经元。 分离培养和器官型切片培养中的海马神经元 将被研究。用膜片钳记录突触后反应 技术.谷氨酸和GABA将被施加到原位树突受体 我们最近使用了一种新的快速聚焦光解方法， 开发这一创新使我们能够克服主要的技术难题， 这些问题使这些基本问题以前无法解决。

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.