γ-氨基丁酸参与家鸽顶盖的视网膜抑制性传入作用的离体研究

In vitro study on the inhibitory effect of the optic tectum input from the retina mediated by γ-aminobutyric acid in pigeon

在 60例家鸽顶盖脑片上 ,利用胞外记录研究了γ 氨基丁酸 (γ aminobutyricacid,GABA)和荷包牡丹碱(bicuculline,BIC)对顶盖视网膜接受区神经元自发放电及刺激Ⅰ层诱发的抑制反应的影响 .灌流GABA ( 1～ 1 0mmol/L)抑制了 60个神经元中的 52个神经元的电活动 ,这些抑制效应呈剂量依赖关系 .GABA的抑制效应绝大部分可被GABAA 受体拮抗剂BIC所阻断 .单独灌流BIC对神经元主要起兴奋作用 .在刺激顶盖Ⅰ层诱发的抑制反应单位上 ,分别灌流BIC和士的宁 (strychnine,STR) ,可见BIC能有效阻断抑制反应 ,而STR不能阻断抑制反应 .这些结果表明 :家鸽顶盖视网膜接受区神经元膜上存在GABAA 受体 ,视神经末梢很可能释放GA BA并通过GABAA 受体起作用 ,从而间接提示GABA可能作为视网膜抑制性传入的神经递质参与视信息在顶盖内的传递和处理 .

Effects of γ aminobutyric acid(GABA) and bicuculline(BIC) on the spontaneous discharge and the inhibitory response to layer Ⅰ stimulation were studied in the retino recipient zone of pigeon optic tectum with the use of brain slices and the glass microelectrode recording techniques. Bath application of GABA(1～10 mmol/L) dose dependentedly inhibited the electrical activity of 52 out of 60 tested neurons. The inhibitory effect of GABA could be blocked by GABA A receptor antagonist BIC. When perfused with BIC alone, the firing rates of most of the tested neurons were significantly increased. BIC could block the inhibitory response to layer Ⅰ stimulation, while the strynine did not. These results show that there is GABA A receptor in the retino recipient zone neurons of optic tectum, and the optic nerve endings may release GABA which acts through GABA A receptor. This indicates GABA may as a neurotransmitter of the retina inhibitory input involving in processing of the visual information in pigeon optic tectum.