IV. Influence of Vestibular Stimulation

Guinea pigs were given transtympanic dosages of neomycin followed by three hours of either vestibular stimulation or immobilization to test the hypothesis that inner ear hair cell membrane permeability is increased for drugs as a consequence of the transduction process. It was found, however, that neither the topographic pattern nor the degree of hair cell damage differed between the two groups. It is concluded that if the transduction process is accompanied by cell membrane permeability changes, the effect is not an increased susceptibility to neomycin toxicity. A measurable effect of stimulation was the significant decrease in the standard deviation of the mean dosage-damage response at each dosage level. This increase in reliability probably resulted from mixing of the inner ear fluids (especially in the vestibular compartment) which encouraged consistent dosages to the hair cells with each repeated trial. Finally, the impact of these findings on hypotheses related to the mechanism of selective ototoxicity is discussed briefly.