MECHANISMS AND EFFECTS OF TRANSEPITHELIAL POLARIZATION IN THE ISOLATED SEMICIRCULAR CANAL

Previous studies have shown that galvanic stimulation of semicircular canal organs can modulate their afferent discharge. However, it has no t been resolved whether this modulation derived from direct stimulatio n of hair cells, afferent nerve fibers, some combination of the two, o r some as yet unknown path. This problem is addressed in the present s tudy. Experiments were designed first to determine the gross current p ath necessary for the DC current to modulate afferent firing. These le d to the conclusion that the current path had to flow between endolymp h and perilymph across the neuroepithelium. Next, the various componen ts in this established path were considered: the afferents, the hair c ells, between the hair cells, or some combination of the three. These experiments led to the conclusion that the current pathway was across the hair cells causing transmitter release and thus affecting afferent activity. (C) 1998 Elsevier Science B.V. All rights reserved.