The spontaneous neuronal activity of the lateral (LVN) and the superior (SVN) vestibular nuclei was analysed before and after the intravenous (i.v.) injection of diazepam in'encephale isolea' decerebrate and cerebellec-tomized rabbits. The inhibition of vestibular neurons was dependent on the integrity of cerebellar connections with LVN. while these links were partially responsible for the diazepam inhibition on SVN. A role of spinal and teledie-mesencephalic structures was not recognized. Considering that diazepam does not increase the activity of Purkinje cells, the drug effect ought to be exerted at the level of the Purkinje cell junctions with the cerebellar nuclei and with the vestibular neurons. GABA being the neurotransmitter released by Purkinje cells evidence is provided for a diazepam potentiation of the GABAergic mechanism at the level of vestibular system.
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