Transtympanic tetrodotoxin alters the VOR and Fos labeling in the vestibular complex

The sodium channel blocker tetrocdotoxin (TTX) is an effective tool for blo ckade of action potentials. Unilateral transtympanic administration of 3 mM TTX produced behavioral symptoms similar to those following unilateral per ipheral vestibular ablation. Complete resolution of visible symptoms occurr ed between 48 and 72 h post-TTX. Eye-coil recordings indicated a spontaneou s nystagmus and a decrease in the VOR in TTX-treated animals. Neuronal acti vity in the central vestibular complex (VC), as monitored with Fos immunocy tochemistry, revealed an asymmetric pattern of Fos labeling in the medial, inferior and superior vestibular nuclei and the prepositus hypoglossal nucl eus. Although the spatio-temporal pattern of Fos labeling was consistent an d reproducible at each time-point, changes were noted among time-points. Tr ansient blockade with TTX may be useful for studying the central vestibular response to recurrent or episodic vestibular disruption in the intact syst em. NeuroReport 12:3051-3055 (C) 2001 Lippincott Williams & Wilkins.