Modulation of rat medial vestibular nucleus neurone activity by vasopressin and noradrenaline in vitro

In the present study, we examined the effects of bath application of vasopressin and noradrenaline on the spontaneous tonic discharge of medial vestibular nucleus (MVN) neurones and investigated if there is an interaction between the two drugs in an in vitro slice preparation of the rat brainstem containing the MVN. The results showed that vasopressin did not affect the spontaneous discharge rate of MVN neurones when applied either as a 60 s pulse or when the drug continuously perfused the slice for a period of 10 min. In contrast, noradrenaline affected the spontaneous discharge rate of the majority of cells tested (53/60, 88%). Noradrenaline excited the majority (46/53, 87%) of MVN neurones through both alpha1 and beta noradrenergic receptor-linked mechanisms. The remaining cells (7/53, 13%) were inhibited by noradrenaline through an alpha2 noradrenergic receptor-linked mechanism. Neither the excitatory nor inhibitory effects of noradrenaline were modified by vasopressin when the two drugs were applied together. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.