OFF PATHWAY IS PREFERENTIALLY SUPPRESSED BY THE ACTIVATION OF GABA(A)RECEPTORS IN CARP RETINA

This study examines the effect of gamma-aminobutyric acid (GABA) on th e ON and OFF pathways in isolated, superfused carp retina. In most (76 %) af amacrine cells bath-applied GABA preferentially suppressed the O FF response. The effect of GABA was blocked by bicuculline. Baclofen d id not cause a similar effect, Furthermore, GABA produced a substantia l suppression of the OFF bipolar cell response, We conclude that the p referential suppression of the OFF pathway may be due to a presynaptic inhibition mediated via GABA(A) receptors at the terminals of OFF bip olar cells.