[Effect of GABA antagonists on the rat electroretinogram]

It has been shown that gamma-aminobutyric acid (GABA) is densely packed in the inner nuclear and plexiform layers in the rat retina, where it is mainly located within a subgroup of amacrine cells. This study examined the effects on the electroretinogram of GABA antagonists infused into the vitreous cavity of urethan-anesthetized rats. Infusions of the GABAA antagonist, bicuculline (0.1-10 mM, 3 microliters) significantly enhanced the b-wave amplitude and reduced the oscillatory potentials (OPs). Similar effects were also produced by infusions of the GABAB antagonist, phaclofen (10 mM, 3 microliters), although lower doses (0.1-1 mM, 3 microliters) had no effect. These results suggest that the actions of GABA, presumably released from amacrine cells, on both GABAA and GABAB receptors are involved in the normal generation of the b-wave and OPs.