1988 Volume 1988 Issue Supplement27 Pages 1-16
The effect of Gentamicin on the vestibular system was studied using bullfrogs. The ototoxicity was compared using 3 different routes of administration, i. e., intraperitoneally (IP), intramuscularly (IM) and intralabyrinthine (IL). Morphological change of the posterior canal crista was observed by SEM. The poterior canal am pullary nerve action potentials (AP) in response to 3 classes of mechanical endo- lymphatic flow were recorded. The change in AP maximum spike count was compared with SEM findings of the sensory epithelia.
SEM revealed no damage in the crista of IP-injected animals. In IM-injected animals, mild changes were found. IL injection, however, resulted in servere damage. The damage started at the portion between the center and the periphery of the ctista and developed toward the center and finally toward the periphery. The damage also progressed with the lapse of time after injection, indicating “delayed ototoxicity”. Changes in the AP were already noticed even in the animals without damage in the surface structure. Decrease in the AP maximum spike count was minimum in IP-injected animals and was maximum with IL injection. With any type of injection, the decrease in the AP tended to correlate with the degree of the damage in the sensory epithelia. The bullfrog may serve as a good model for evaluating both physiological and morphological effects of ototoxicity
