Otis T S, Staley K J, Mody I
Department of Neurology and Neurological Sciences M016, Stanford University School of Medicine, CA 94305.
Brain Res. 1991 Apr 5;545(1-2):142-50. doi: 10.1016/0006-8993(91)91280-e.
Miniature spontaneous inhibitory postsynaptic currents (sIPSCs) mediated by GABAA receptors were recorded using whole-cell patch clamp recordings in rat brain slices maintained in vitro at 34 +/- 1 degree C. We have found that firing of action potentials by principal neurons or by GABAergic interneurons is not necessary to the generation of sIPSCs since they persist in the presence of 1-5 microM tetrodotoxin (TTX). The average frequency of the discrete sIPSCs exhibits a large cell-to-cell variability and is between 5-15 Hz. The amplitudes of the sIPSCs depend on the difference between the membrane potential and the equilibrium potential for Cl- (ECl). Generally, 70-80 mV away from ECl, sIPSCs have a mean amplitude of 30-80 pA (i.e. peak conductance of 400-1000 pS) with an average decay time constant of 5.8 ms. Accordingly, unitary single sIPSCs arise from the simultaneous activation of no more than 20 GABAA receptor/channels. The perpetual barrage of spontaneous GABAergic activity is very likely to be a critical factor in the regulation of neuronal excitability and the mechanism of action of several neuroactive compounds.
在体外维持于34±1摄氏度的大鼠脑片中，使用全细胞膜片钳记录法记录由GABAA受体介导的微小自发性抑制性突触后电流（sIPSCs）。我们发现，主神经元或GABA能中间神经元产生动作电位对于sIPSCs的产生并非必要，因为在存在1 - 5微摩尔河豚毒素（TTX）的情况下它们依然存在。离散sIPSCs的平均频率表现出较大的细胞间差异，介于5 - 15赫兹之间。sIPSCs的幅度取决于膜电位与氯离子平衡电位（ECl）之间的差值。一般来说，在距离ECl 70 - 80毫伏时，sIPSCs的平均幅度为30 - 80皮安（即峰值电导为400 - 1000皮西门子），平均衰减时间常数为5.8毫秒。因此，单一的sIPSCs源于不超过20个GABAA受体/通道的同时激活。自发性GABA能活动的持续冲击很可能是调节神经元兴奋性以及几种神经活性化合物作用机制的关键因素。
