The role of γ-aminobutyric acid and its receptors in the nucleus of basal optic root in pigeons

The effects of γ-aminobutyric acid (GABA) and its antagonists bicuculline and 2-hydroxysaclofen on neuronal firings in the nucleus of basal optic root (nBOR) in pigeons were studied by using extracellular recording and microiontophoretic techniques. The results suggest that GABA may be an inhibitory neurotransmitter or modulator within nBOR, functioning by means of main mediation of GABAA receptors and of minor mediation of GABAB receptors. Furthermore, GABA and its GABAA receptors are involved in the modulation of directional selectivity in part of nBOR neurons.     

Gamma-aminobutyric acid and GABA_A receptors are involved in directional selectivity of pretectal neurons in pigeons

The present study describes the effects of gamma-aminobutyric acid (GABA) and its antagonists, bicuculline and 2-hydroxysaclofen, on visual responses of neurons in the pigeon nucleus lentiformis mesencephali (nLM). The results indicate that GABA significantly reduces both spontaneous activity and visual responsiveness, and GABAA antagonist bicuculline but not GABAB antagonist 2-hydroxysaclofen enhances visual responses of nLM cells examined. Furthermore, inhibition produced by motion in the null-direction of pretectal neurons is diminished by bicuculline but not by 2-hydroxysaclofen. It is therefore concluded that the null-direction inhibition of directional cells in the pigeon nLM is predominantly mediated by GABA and GABAA receptors. This inhibition may at least in part underlie directional asymmetry of optokinetic responses.     

γ-氨基丁酸及其GABAA受体参与家鸽顶盖前核神经元方向选择性的形成

研究了-氨基丁酸(GABA)及其拮抗剂荷包牡丹碱和2-hydroxysaclofen对家鸽中脑扁豆核神经元视觉反应的影响. 结果指出, GABA能明显减小扁豆核神经元的自发活动和视觉反应, 其GABAA拮抗剂荷包牡丹碱则能增强视觉反应, 并可消除无效方向上的抑制性反应, 但GABAB拮抗剂2-hydroxysaclofen对视觉反应和抑制反应均无效. 由此可见, 家鸽中脑扁豆核方向敏感神经元无效方向上的抑制主要由GABA和GABAA受体介导. 这种抑制作用至少部分是视动震颤方向不对称性的基础.     

γ-氨基丁酸及其受体在家鸽基底视束核中的作用

采用细胞外记录和微量离子电泳技术,研究了γ-氨基丁酸(GABA)及其拮抗剂荷苞牡丹碱和2-hydroxysaclofen对家鸽基底视束核(nBOR)神经元的作用.实验结果表明,GABA是该核团内的一种抑制性递质或调质,且主要通过GABA_A受体起作用,GABA_B受体则起较小作用.另外,GABA通过GABA_A受体参与nBOR部分神经元的方向选择性调制.