EXPERIMENTAL STUDIES IN SENSORY PATHWAYS

正常的基底神经节功能高度依赖于SNc中的多巴胺能（DA）神经元和SNr/EP中的gaba能神经元的活动。然而，控制SNc和SNr神经活动影响多巴胺和GABA在其投射靶点释放的机制的许多方面仍未得到很好的了解。最近，人们对从被盖的桥脚核（PPN）和丘脑底核（STN）向SNc DA和SNr GABA神经元的收敛输入越来越感兴趣。虽然这些输入的功能作用尚不清楚，但我们之前的研究表明，PPN的乙酰胆碱（ACh）输入通过增加阳离子流入和减少K+流出的结合，使DA和GABA神经元的静息膜电位去极化，并在起搏器样缓慢去极化（PLSD）期间减少Ca2+进入，从而减少超极化后随后的峰值的幅度和持续时间。因此，我们假设(1)ACh的作用增加了SNc DA和SNr gabaergy神经元对来自STN和PPN的谷氨酸能（glu）输入的响应而表现出突发放电的倾向；(2)除了PPN和STN的glu和ACh兴奋性投射外，gabaergy向SN的抑制性投射（通过阶段性抑制SNr神经元引起GABA系统的去抑制）也调节SNc DA和SNr gabaergy神经元的放电行为。为了验证这些假设，我们将利用新开发的由PPN、SN、STH和STR组成的体外器官型培养制剂进行形态学和电生理研究。形态学研究将涉及光和电子显微镜(1)识别,glu和GABA ergic投影模式及其终端站点SNc DA和信噪比GABA神经元,(2)识别核起源ACh和glu预测SNc DA和信噪比GABA ergic神经元结合生物胞素细胞内标签,和(2 b)识别细胞的位置标记生物胞素终端与SNc DA和信噪比GABA神经元突触和(3)确定的位置,SNc DA和SNr GABA神经元上的glu和GABA受体。电生理研究将包括使用全细胞（电流）钳或细胞内锋利电极记录来描绘(1)胆碱能受体激活对PLSD和AHP期间Ca2+进入的影响，(2)PPN和STN的兴奋性突触输入和STR的gaba能抑制输入对SNc DA和SNr gaba能神经元的放电特性和破裂的影响。了解多重输入在控制和/或调节SNc和SNr细胞活动（影响其靶结构（即纹状体和丘脑））中的作用，对于运动和行为功能以及帕金森病等临床实体具有重要意义。

Normal basal ganglia function is highly dependent on the activities of dopaminergic (DA) neurons in the SNc and GABAergic neurons in SNr/EP. However, many aspects of the mechanisms controlling SNc and SNr neural activity which influence dopamine and GABA release at their projection targets are still not well understood. Recently there has been a growing interest in converging inputs from the tegmental pedunculopontine (PPN) and subthalamic nucleus (STN) to the SNc DA and SNr GABA neurons. Although the functional role of these inputs is poorly understood, our previous studies suggested that acetylcholine (ACh) inputs from PPN depolarize the resting membrane potential of DA and GABA neurons by a combination of increased cationic influx and decreased K+ efflux, and reduces Ca2+ entry during the pacemaker-like slow depolarization (PLSD), which decreases the amplitude and duration of the subsequent spike after hyperpolarization. We, therefore, hypothesize that (1) the action of ACh increases the tendency for SNc DA and SNr GABAergic neurons to exhibit burst firing in response to glutamatergic (glu) input from the STN and PPN and (2) in addition to glu and ACh excitatory projections from the PPN and STN, but also GABAergic inhibitory projections to SN (causing disinhibition of GABA system by phasic inhibition of the SNr neurons) are modulating SNc DA and SNr GABAergic neuronal firing behavior. To test these hypothesis, we will utilize the newly developed in vitro organotypic culture preparation consisting of PPN, SN, STH and STR to conduct morphological and electrophysiological studies. Morphological studies will involve light and electron microscopy to (1) identify ACh, glu and GABAergic projection patterns and their terminal sites on the SNc DA and SNr GABA neurons, (2a) identify the nuclear origin of ACh and glu projections to SNc DA and SNr GABAergic neurons with a combined biocytin intracellular labeling, and (2b) identify the locations of the intracellularly labeled biocytin terminals making synapses with SNc DA and SNr GABA neurons and (3) identify the location of ACh, glu and GABA receptors on the SNc DA and SNr GABA neurons. Electrophysiological studies will involve use of whole-cell (current) clamp or intracellular sharp electrode recording to delineate the effect of (1) cholinergic receptor activation on Ca2+ entry during the PLSD and AHP,(2) the effect of excitatory synaptic inputs from PPN and STN and GABAergic inhibitory inputs from the STR on firing properties and bursting of SNc DA and SNr GABAergic neurons. Understanding the role of multiple inputs in the control and/or modulation of SNc and SNr cellular activity which affect their target structures (i.e. striatum and thalamus) is of fundamental importance relative to motor and behavioral function as well as clinical entities such as Parkinson's disease.