抄録
Department of Pathology, Instiute for the Deaf, Tokyo Medical and Dental University The present studies were made to clarify the histopathological and enzyme-histochemical findings of the internal ears in the guinea pigs receiving gentamicin (25 mg/kg/day intramuscularly for 7 days) and kanamycin (400 mg/kg/day intramuscularly for 4 weeks). Pinna reflex threshold was measured by the audiometer for the guinea pig before, during and after the experiment. Although no specific vestibular function test was performed, there was no ataxia in all of the experimental animals. The pinna reflex thresholds were within normal limits in all of the 23 animals given gentamicin. On the other hand, the thresholds were increased slightly in one of the 20 animals receiving kanamycin and markedly in 2 of them. The internal ears including the organ of Corti of the cochlea as well as the vestibular apparatus were histopathologically free from any damage and succcinic dehydrogenase of the hair cells of the organ of Corti was histochemically considerably active in all of the animals given gentamicin. Of the 20 animals receiving kanamycin one showed histopathologically severe damage of the organ of Corti and exhibited slight distention of the cochlear duct. 'Loss of succinic dehydrogenase activity of the hair cells of the organ of Corti was extensive in one animal given kanamycin and limited to the first turn of the cochlea in other one.
Consequently, it is concluded that the short-term intramuscular administration of gentamicin (25 mg/ kg/day) did not cause any damage of the organ of Corti and vestibular apparatus in the guinea pig. This result suggests that the usual dosage of gentamicin injectable (0. 8 to 1. 2 mg/kg/day) will be able to administer intramuscularly for 7 days without any impairment of hearing and equilibriUm in the patient with normal renal function.
