Oyama Y, Ikemoto Y, Kits K S, Akaike N
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
Eur J Pharmacol. 1990 Aug 21;185(1):43-52. doi: 10.1016/0014-2999(90)90209-o.
The effects of gamma-aminobutyric acid (GABA) on the glutamate receptor chloride ion (Cl-) channel complex were examined in mechanically isolated and internally perfused Aplysia neurons using a concentration clamp technique. GABA at concentrations of 3 x 10(-6) M or more, concentration dependently delayed the recovery of the glutamate response from desensitization. This effect was independent of the GABA response and Cl- redistribution. Muscimol (10(-4) M) mimicked the effect of GABA. However, this was not the case for baclofen (10(-3) M). In some isolated neurons, GABA at concentrations of more than 10(-4) M clearly induced an additional Cl- current, the current kinetics of which were different from those induced by lower concentrations of GABA. Even in the continued presence of 10(-4) M GABA, which desensitized the fast GABA response, higher concentrations of GABA (3 x 10(-4) M to 10(-2) M) elicited the additional current in a concentration-dependent manner. The presence of 10(-4) M glutamate completely abolished this current, indicating cross-desensitization between the glutamate and slow GABA responses. High concentrations of GABA (3 x 10(-2) M) did not activate the glutamate receptor coupled to the large cation channel. The results suggest that, in Aplysia neurons, the glutamate receptor-Cl- channel complex has some similarities to the GABA receptor-Cl- channel complex.
采用浓度钳技术，在机械分离并进行内部灌流的海兔神经元中，研究了γ-氨基丁酸（GABA）对谷氨酸受体氯离子（Cl-）通道复合物的影响。浓度为3×10（-6）M或更高的GABA，浓度依赖性地延迟了谷氨酸反应从脱敏状态的恢复。这种效应独立于GABA反应和Cl-再分布。蝇蕈醇（10（-4）M）模拟了GABA的作用。然而，巴氯芬（10（-3）M）并非如此。在一些分离的神经元中，浓度超过10（-4）M的GABA明显诱导出额外的Cl-电流，其电流动力学与较低浓度GABA诱导的不同。即使在持续存在使快速GABA反应脱敏的10（-4）M GABA的情况下，更高浓度的GABA（3×10（-4）M至10（-2）M）仍以浓度依赖性方式引发额外电流。10（-4）M谷氨酸的存在完全消除了该电流，表明谷氨酸和缓慢GABA反应之间存在交叉脱敏。高浓度的GABA（3×10（-2）M）未激活与大阳离子通道偶联的谷氨酸受体。结果表明，在海兔神经元中，谷氨酸受体-Cl-通道复合物与GABA受体-Cl-通道复合物有一些相似之处。
