EFFECTS OF BACLOFEN ON MEDIAL VESTIBULAR NUCLEUS NEURONS IN GUINEA-PIG BRAIN-STEM SLICES

Using intracellular recordings of medial-vestibular nucleus neurones ( MVNn) in guinea-pig brainstem slices, the effects of baclofen, a speci fic agonist of the metabotropic GABAB receptors, were tested on the th ree main types of MVNn (A, B and B + LTS MVNn) that were previously id entified in this nucleus. Regardless of their type, almost all MVNn we re hyperpolarized and inhibited by baclofen. These hyperpolarizing eff ects persisted following either the addition of tetrodotoxin (TTX) in the perfusion medium, or in the presence of a high Mg2+/low Ca2+ solut ion known to block synaptic transmission. These results demonstrate th at all types of MVNn are endowed with postsynaptic GABA(B) receptors.