On GABAergic mechanisms in the optokinetic nystagmus of the frog: effects of bicuculline, allylglycine and SR 95103, a new GABA antagonist.

In a monocular situation, an intravitreal injection of the GABA antagonists, bicuculline or SR 95103 provoked both the suppression of the optokinetic nystagmus (OKN) related to the injected eye and the appearance of a Nasal-Temporal (N-T) component in the OKN triggered by the contralateral non-injected eye (this N-T component being absent in control OKN). These two effects were added in a binocular condition. Similar results were obtained with L-C allylglycine which reduces the endogenous GABA level, but these effects were delayed when compared to those of GABA antagonists. All these data are roughly analogous to those previously obtained with picrotoxin (a non-competitive GABA antagonist) and thus confirm that GABA mechanisms are involved in the control of the frog OKN. Furthermore, SR 95103 acted in this model as a potent selective GABA antagonist, as has been demonstrated in another system.