シンポジウム発表の要旨(姜):

大脳皮質各層の錐体細胞より細胞内記録を行い、APV 及びCNQX の存在下で細胞の近傍に格子状に微小刺激を与え、GABA(A) 及びGABA(B) IPSPs を誘発し、それぞれの時空間パターンの解析を行った。その結果、GABA(A) 及びGABA(B) 型の応答は、それぞれ、皮質層構造に対して水平方向及び垂直方向の広がりをもって誘発された。また、GABA(B) 型の応答は、GABA(A) 型の応答に比べて、時空間的により分散した入力により発生していることも示唆された。これらのことは、皮質内分布を異にする二群の抑制性介在細胞によるGABA(A) 及びGABA(B) 受容体の選択的支配を示唆するが、現在までに知られている抑制性介在細胞との関係について討論・考察を行いたい。一方、錐体細胞の興奮性は、カルシウム依存性カチオン電流により担われた脱分極性スパイク後電位 (DAP) 及び過分極性スパイク後電位とのバランスにより決定されることが明らかになりつつある。この DAP は、GABA(A) 及びGABA(B) 抑制系による修飾作用を受けていた。

Intracellular recordings were obtained from pyramidal cells located in layers II-VI. GABA(A) and GABA(B) IPSPs were induced by microstimulation applied in a grid pattern in the vicinity of the recorded cells. GABA(A) responses were maximally produced by stimulation of the layer where the cell body of the recorded pyramidal cell was located, and they decreased in amplitude as the more superficial layer was stimulated. In contrast, GABA(B) responses were maximally induced by stimulation of layer II regardless of the location of the recorded pyramidal cell, and decreased in amplitude as the deeper layer was stimulated. The maximum horizontal distance over which GABA(A) responses could be evoked (800-1200 mm) was much larger than that for GABA(B) responses (340-680 mm). GABA(B) responses appeared to be brought about by more spatiotemporally dispersed inputs presumably along apical dendrites of pyramidal cells, while GABA(A) responses appeared to be brought about by spatiotemporally restircted inputs. These differential spatiotemporal patterns of GABA(A) and GABA(B) IPSPs suggest the presence of two distinct types of inhibitory interneurons, which are distributed differentially by layers and have horizontally spreading and vertically descending axons, respectively. On the other hand, it is generally believed that the excitability of pyramidal cells is regulated by the balance between spike-afterdepolarization (ADP) and spike-afterhyperpolarization (AHP). The ADP was found to be affected by activation of GABA(A) and GABA(B) inhibition using whole-cell recording method.

Updated, 30 Mar 96.


大脳皮質に関する研究論文のリスト:

1. Kang, Y. (1995) Differential paired pulse depression between non-NMDA and NMDA currents in pyramidal cells of rat frontal cortex. J. Neuroscience 15: 8268-8280.

2. Kang, Y & Kayano, F.(1994) Electrophysiological and morphological characteristics of layer VI pyramidal cells in the cat motor cortex. Journal of Neurophysiology 72: 578-591.

3. Kang, Y., Kaneko, T., Ohishi, H., Endo, K. & Araki, T. (1994) Spatio-temporally differential inhibition of pyramidal cells in the cat motor cortex. Journal of Neurophysiology 71: 280-293


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