細胞膜の電気生理学的特性に基づくラット黒質緻密部の神経細胞分類について

摘要

In this study, to aim to understand characteristics of local circuits in substantia nigra pars compacta (SNc) of basal ganglia, we carried out electrophysiological experiments for rat midbrain slices at the single cell level. To investigate a possibility to classify neurons in SNc into several cell-types, especially, we recorded membrane voltage and current signals from individual neurons using a patch-clamp recording technique. Firstly, our results showed, as reported in previous studies, that neurons were classified into two cell-types; principal cells (PCs) and secondary cells (SCs). Firing rate in most of the PCs was lower than that in the SCs, and spike width in the PCs was wider than that in the SCs. Secondly, we immunochemically tested if the PCs were dopaminergic (DA) neurons and knew that non-DA neurons were included in the PCs. Thirdly, we tried to findrnsubtypes in the SCs on the basis of obtained electrophysiological data. However, our analysis indicated that it is difficult to classify the SCs into several subtypes, because of continuous cell distribution in a space of some characteristic parameters of firing properties.%本研究では，大脳基底核黒質緻密部の局所回路特性の理解を目指して，ラヅト脳切片を用いて神経細胞の電気的特性を実験的に調べた．特に，黒質の神経細胞の電気生理学特性に基づく細胞分類の可能性を検討する為に，ホールセルバッチクランプ法を用いて細胞の膜電位と電流を計測した．その結果，まず，先行研究が示すように，活動電位の幅が広く低周波数で発火する神経細胞（第一細胞）と活動電位の幅が狭く高周波数で発火する神経細胞（第二細胞）の二種類に分類できた．次に，免疫組織化学法を用いて，電気活動を計測した第一細胞がドーパミン作動性（DA）であるかを調べた．その結果，第一細胞には，DAと非DAが混在していることが判った．さらに，第二細胞群をいくつかの電気的特徴からサブタイプに分類できるかを検討した．細胞間には，その特徴が大きく異なっているものが存在するが，細胞群全体の特徴パラメータはその空間上に連続的に分布しており，単純な基準ではサブタイプに分類することが困難であることが判明した．