Inhibitory effects of tandospirone, a 5-HT1A agonist, on medial vestibularnucleus neurons responding to lateral roll tilt stimulation in rats

An electrophysiological study was performed using chloral hydrate-anestheti zed rats to determine whether tandospirone, a 5-HT1A agonist, affects neuro nal activities of the medial vestibular nucleus (MVN), since serotonergic i nnervation and 5-HT1A receptors are present in this nucleus. Tandospirone a pplied microiontophoretically at a current of 20-60 nA caused an inhibition of tilt-induced firing of alpha -type neurons, which showed increased and decreased firing with lateral tilt ipsilateral and contralateral to the rec ording site, respectively, along with that of beta -type neurons which exhi bited the reverse responses to ipsilateral and contralateral tilt stimulati on. The inhibition was antagonized during simultaneous, iontophoretic appli cation of WAY-100635 (20-60 nA), a 5-HT1A receptor antagonist, although WAY -100635 alone rarely affected spontaneous or tilt-induced firing in either type of neurons. These results suggest that tandospirone acts on a 5-HT1A r eceptor to inhibit transmission of otolith information to alpha- and beta - type MVN neurons. (C) 2001 Elsevier Science B.V. All rights reserved.