Direct and indirect effects of XXXX on medial vestibular nucleus neurones in guinea-pig brainstem slices.

@entity1522 @entity6341 @entity1246 @entity1027 @entity1022 @entity4524 @entity141
Inhibitory @entity1522 are considered as major transmitters in the vestibular system. Using intracellular recordings in slices, we applied @entity1246 ( @entity1246 ) and @entity6341 (a specific agonist of the GABAA receptor) to the two main types of medial vestibular nucleus neurones (A and B MVNn). In either a high Mg2+/low @entity141 solution, or a solution containing tetrodotoxin, all MVNn were hyperpolarized by @entity1246 and @entity6341 . This indicates that both types of MVNn are endowed with postsynaptic, hyperpolarising GABAA receptors. In a normal medium, about half of A and B MVNn were, in contrast, depolarised by @entity1246 and @entity6341 , whereas the remaining cells were hyperpolarised. These results could be due to a modulation by @entity1246 and @entity6341 of a tonic @entity1246 release in the slice. Such a release was, indeed, suggested by results showing the depolarising effect of either @entity1022 ( @entity4524 ) or @entity1027 , when applied alone. The cells that were depolarised by @entity1246 or @entity6341 in control conditions were always hyperpolarised in the presence of @entity4524 . Our data therefore suggest that @entity1246 acting at GABAA receptors in the medial vestibular nucleus can play a role either through a postsynaptic hyperpolarising action or indirectly by inhibiting a tonic @entity1246 release, probably resulting from the spontaneous activity of local inhibitory interneurones. A GABAergic regulation of these interneurones could be important in processes of vestibular habituation and/or adaptation.
