Calcium channels functional roles in the frog semicircular canal

Different types of voltage-operated calcium channels have been described in hair cells; however, no clear functional role has been assigned to them. A s a first functional characterization of vestibular calcium channels, we st udied the effect of several calcium channel agonists and antagonists on who le nerve firing rate in an isolated frog semicircular canal preparation. Re sting activity was affected by all dihydropyridines tested and by omega-con otoxin GVIA, whereas only nimodipine was able to reduce the mechanically ev oked activity. These results indicate that nimodipine-sensitive channels pl ay a major role in afferent transmitter release, and w-conotoxin GVIA sensi tive channels regulate the afferent firing (possibly on the postsynaptic si de) but with a less important role. NeuroReport 11:417-420 (C) 2000 Lippinc ott Williams & Wilkins.