Inhibition of calcium signaling in terminal and soma of carp retinal bipolar cells by GABA  

GABA抑制鲫鱼视网膜双极细胞的轴突末梢和胞体内的钙信号(英文)

作　　者：吴迪[1] 朱培闳[1] 

机构地区：[1]中国科学院上海生理研究所,上海中国200031

出　　处：《Acta Pharmacologica Sinica》2000年第8期40-45,共6页中国药理学报（英文版）

摘　　要：To investigate the effect of activation of y-aminobutyric acid (GABA) receptors on high K+-evoked Ca2+ signaling in the terminal and soma of carp retinal ON-type bipolar cells. METHODS: Freshly dissociated carp retinal cells were loaded with fluo-3AM and then the fluorescence measurements were performed on a confocal laser-scanning microscope. RESULTS: Ca2+ signaling evoked by high K+ 35 mmol/L was completely suppressed in both the terminal and soma of bipolar cells by GABA 100μmol/L. However, different results were found in the terminal and soma when only one subtype of GABA receptors was activated. While activation of either GABAA or GABAc receptors totally suppressed Ca2+ signaling in the soma, a gradual elevation of [Ca2+]i appeared in the terminal. GABA 10 μmol/L could also completely suppress Ca2+ signaling in the soma, but could only partially reduce Ca2+ signaling in the terminal. CONCLUSION: Activation of both GABAA and GABAc receptors could completely inhibit high K+-evoked Ca2+ signaling in the terminal and soma of carp retinal ON-type bipolar cells. While activation of either GABAA or GABAc receptors alone still totally suppressed Ca2+ signaling in the soma, a gradual elevation of [Ca2+]i appeared in the terminal, which may be due to desensitization of GABA receptors.目的:研究GABA受体的激活对于鲫鱼视网膜ON-型双极细胞的胞体和轴突末梢内高钾引起的钙信号的影响。方法:急性分离的鲫鱼视网膜细胞经fluo-3AM孵育后,用激光共聚焦显微镜检测荧光变化。结果:GABA 100μmol/L可以完全抑制双极细胞胞体和轴突末梢内高钾35mmol/L引起的钙信号。仅激活GABA受体的一种亚型时,轴突末梢和胞体内出现了不同的结果。当GABA_A受体或GABA_C受体被单独激活时,尽管胞体内的钙信号仍旧被完全抑制,但轴突末梢的[Ca^(2+)]_i逐渐升高。GABA 10μmol/L仍旧可以完全抑制胞体内的钙信号且部分抑制轴突末梢内的钙信号。结论:激活GABA_A和GABA_C受体能够完全抑制鲫鱼视网膜ON-型双极细胞内高钾引起的钙信号。仅激活GABA_A或GABA_C受体时可以完全抑制胞体内的钙信号,而轴突末梢的[Ca^(2+)]_i逐渐升高,这可能与GABA_A或GABA_C受体的脱敏有关。

关 键 词：GABAa receptors GABAc receptors bipolar cells RETINA 

分 类 号：Q42[生物学—神经生物学]