HIPPOCAMPAL INHIBITION--CIRCUITRY AND MATURATION

拟议项目的总体目标是进一步加强我们的 理解抑制性神经元的连接和成熟 海马体中的回路 直到最近，人们才相信 海马中抑制的激活依赖于 通过前馈和反馈途径，谷氨酸介导的兴奋。 我们最近的研究表明，抑制性中间神经元可以 也可以通过两种不需要谷氨酸的途径来募集， 介导的神经传递：（1）通过GABA的去极化作用 对来自突触连接的中间神经元的BABA/A受体的影响，以及（2） 通过假定的电紧张耦合。 拟议的研究将进一步 这些新的谷氨酸非依赖性抑制剂， 同步过程。 体外海马实验 将进行切片以解决三个主要问题。 这些是（1） 证实了一个亚群之间的电紧张性耦合 （2）分析中间神经元的形态，以确定 功能分化的结构相关因素 （3）确定中间神经元的亚群; 这些谷氨酸非依赖性同步化的发育概况 未成熟大脑中的突起 所有实验都将涉及 细胞内记录从确定的抑制性神经元，在大多数 CA3区锥体细胞5例。 将验证电紧张耦合 直接，使用配对记录，并收集支持性数据 使用细胞内染料标记物来揭示染料偶联的细胞， 挥发性麻醉药的应用和改良 细胞外环境（两种程序都旨在破坏间隙 junctions）。 将进行中间神经元的形态学分析 使用细胞内标记物神经生物素，同时 电生理学分析的内在属性，突触和 电紧张耦合 发展研究将评估 中间神经元的内在成熟和 抑制回路作为一个整体，与其输出到锥体 细胞 抑制回路在正常功能中起着不可或缺的作用 海马体，是必不可少的限制传播， 在癫痫等情况下的异常活动。 我们最近的研究 这表明抑制回路要比 以前实现的。 拟议研究中的实验将 研究这种复杂性，以便我们能够进一步了解 海马体中正常和异常的网络功能。

The overall objective of the proposed project is to further our understanding of the connectivity and maturation of the inhibitory circuit in the hippocampus. Until recently, it was believed that the activation of inhibition in the hippocampus was dependent upon glutamate-mediated excitation, via feedforward and feedback pathways. Our recent studies have demonstrated that inhibitory interneurons can also be recruited through two pathways which do not require glutamate- mediated neurotransmission: (1) via the depolarizing action of GABA on BABA/A receptors from synaptically connected interneurons and (2) via presumed electrotonic coupling. The proposed study will further characterize these novel, glutamate-independent inhibitory synchronization processes. In vitro experiments on the hippocampal slice will be performed to address three major issues. These are (1) confirmation of electrotonic coupling among a subpopulation of interneurons, (2) analysis of interneuron morphology to determine structural correlates for the functional differentiation of interneurons into various subgroups and (3) determination of the developmental profile of these glutamate-independent synchronization processes in the immature brain. All experiments will involve intracellular recording from identified inhibitory neurons and, in most cases, CA3 pyramidal cells. Electrotonic coupling will be verified directly, using paired recordings, and supportive data will be gathered using intracellular dye markers to uncover dye-coupled cells, application of volatile anesthetics and modification of the extracellular milieu (both procedures designed to disrupt gap junctions). Morphological analysis of interneurons will be performed using the intracellular marker Neurobiotin, with simultaneous electrophysiological analyses of intrinsic properties, synaptic and electrotonic coupling. The developmental studies will assess both the intrinsic maturation of interneurons and the maturation of the inhibitory circuit as a whole, as related to its output onto pyramidal cells. The inhibitory circuit plays an integral role in the normal function of the hippocampus, and is essential for limiting the propagation of abnormal activity in conditions such as epilepsy. Our recent studies demonstrate that the inhibitory circuit is much more complex than previously realized. The experiments in the proposed study will examine this complexity so that we can further our understanding of the normal and abnormal network function in the hippocampus.