Possible involvement of K+‐conductance in the action of γ‐aminobutyric acid in the guinea‐pig hippocampus
Possible involvement of K+‐conductance in the action of γ‐aminobutyric acid in the guinea‐pig hippocampus
复制标题
K+电导可能参与豚鼠海马γ-氨基丁酸的作用
DOI：
10.1111/j.1476-5381.1985.tb08923.x
复制
发表时间：
1985
影响因子：
7.3
通讯作者：
N. Ogata
中科院分区：
文献类型：
--
作者：
M. Inoue;T. Matsuo;N. Ogata
1利用豚鼠脑切片研究γ -氨基丁酸（GABA）在海马中的作用机制。GABA在锥体细胞中产生双相反应，包括超极化和去极化成分。当不同浓度的GABA作用于同一神经元时，较低浓度的GABA通常会产生超极化优势反应，而较高浓度的GABA则会产生去极化优势反应。在含有低浓度Cl−的培养基中，GABA响应的去极化成分增强，相对不受外部K+浓度变化的影响，并被微毒素（2 × 10−5 M）阻断。在无Ca2+的培养基中，当Na+浓度降低到13 mM时，GABA的去极化反应持续存在。5低剂量的微毒素和双管碱联合应用消除了GABA双相反应的大部分去极化成分，产生了相对纯粹的超极化反应。从电流-电压关系估计，这种药理学上“孤立”的GABA超极化反应的逆转电位约为- 90 mV，与巴氯芬诱导的超极化反应的逆转电位相同。当膜通过向内直流电注射连续超极化时，“药理学分离”的GABA超极化反应的逆转点与爆发后的超极化一致。7浸泡介质中低浓度的Cl−对GABA响应的超极化部分没有明显影响，但它显著增加了去极化部分的振幅。这些结果表明，GABA在海马中的作用可能涉及K+电导的激活。
1 The mechanism underlying the action of γ‐aminobutyric acid (GABA) in the hippocampus was investigated using guinea‐pig brain slices. 2 GABA either superfused or applied directly by microiontophoresis produced a biphasic response in pyramidal cells, comprising hyperpolarizing and depolarizing components. 3 When different concentrations of GABA were applied to the same neurone, the lower concentrations generally produced a hyperpolarization‐predominant response, while higher concentrations resulted in a depolarization‐predominant response. 4 The depolarizing component of the response to GABA was augmented in a medium containing a low concentration of Cl−, relatively unaffected by a change in external K+ concentration, and blocked by picrotoxin (2 × 10−5 M). The depolarizing response to GABA persisted in a Ca2+‐free medium in which the concentration of Na+ was reduced to 13 mM. 5 Combined application of low doses of picrotoxin and bicuculline eliminated the major part of the depolarizing component of the biphasic response to GABA and produced a relatively pure hyperpolarizing response. The reversal potential of this pharmacologically ‘isolated’ hyperpolarizing response to GABA was estimated, from the current‐voltage relationships, to be about − 90 mV and was the same as that of the hyperpolarization induced by baclofen. 6 When the membrane was successively hyperpolarized by inward direct current (d.c.) injections, the reversal point of the ‘pharmacologically isolated’ hyperpolarizing response to GABA coincided with that of the post‐burst hyperpolarization. 7 Low concentrations of Cl− in the bathing medium had no noticeable effect on the hyperpolarizing component of the response to GABA, whereas it markedly increased the amplitude of the depolarizing component. 8 These results suggest that the action of GABA in the hippocampus may involve an activation of K+ conductance.