Comparative study of the effect of gentamicin on the vestibulo-ocular and visual vestibulo-ocular reflexes in the cat.

The ototoxic effect of an aminoglycoside, gentamicin, on the vestibular system was investigated in cats given daily doses of 40 mg/kg i.m. for 14 days. Periodically, measurements were made of the vestibulo-ocular reflex (VOR) and visual vestibulo-ocular reflex (ViVOR) responses induced by rotatory stimuli at various frequencies from 0.0125 Hz to 0.8 Hz. After the cessation of drug administration, a progressively declining response to VOR stimuli continued, manifested by gain (ratio of peak response to peak stimulus amplitude) and phase relationships. The ViVOR was affected only in the gain measurements. The changes in the response amplitude (gain) were greater for the VOR than for the ViVOR…