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 GABA(A) antagonist bicuculline but not GABA(B) 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 GABA(A) receptors. This inhibition may at least in part underlie directional asymmetry of optokinetic responses.
Xiao
Q
Q
Laboratory for Visual Information Processing, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.
Fu
Y
Y
Hu
J
J
Gao
H
H
Wang
S
S