Further evidence on the contribution of GABAA receptors to the GABA-mediated inhibition of medial vestibular nucleus neurones in vitro.

The present study investigated the electrophysiological effects of the selective and potent GABAA receptor agonist, isoguvacine, on guinea-pig medial vestibular nucleus (MVN) neurones in brainstem slices. The results confirm that many MVN neurones have GABAA receptors and that, even at concentrations as low as 10(-8) M, GABA is capable of exerting a powerful inhibitory effect on these neurones via GABAA receptors. The finding that > 50% of neurones did not respond to isoguvacine, even at concentrations of 10(-6) M, suggested that only a specific subset of MVN neurones have GABAA receptors. Since many type I MVN neurones are believed to have postsynaptic GABAA receptors, it is possible that selective agonists such as isoguvacine may be useful in identifying type I neurones in vitro.