Modulation of Neuronal Activity of Cerebellar Interposed Nucleus By Stimulating Dorsal Raphe Nucleus in The Rat

The effects of stimulating dorsal raphe nucleus (DR) on activity of cerebellar interposed nucleus (IN) was investigated.Stimulation of DR elicited inhibitory,excitatory and biphasic (inhibition-excitation and excitation-inhibition) responses from IN cells.The majority of responsive cells showed an inhibitory response (76.0%) with a latency of less than 30 ms.The spontaneous discharge frequencies of the IN cells were 5 to 120 Hz,and the IN cells with higher discharge frequencies showed low responsive rates to the DR stimulation in comparison with those lower firing frequency cells.Injection of 5-HT 2/1C receptor antagonist methysergide (iv) could block the depressive effect of DR stimulation on the IN cells (85.7%).These results suggest that raphe-cerebellar serotonergic afferent fibers may be involved in the cerebellar sensorimotor integration process by exerting their modulatory action on the deep cerebellar nuclear cells activities.