The active process is affected first by intense sound exposure

Evidence exists to suggest that intense sound releases excess neurotransmitter from the inner hair cells. However, it has been previously reported that intense sound affects the cochlear micromechanics by altering the stereocilia. Therefore, we tested the hypothesis that intense sound affects structures involved in transduction before it affects the nerve endings. In order to test this hypothesis, we examined the interaction of intense sound with kynurenate which blocks the action of the neurotransmitter on the afferent nerve endings. Intracochlear perfusion of artificial perilymph containing 5 mM kynurenate did not reduce the effect of intense sound when we compare the results with a control group perfused with artificial perilymph alone. These results show that blockade of afferent transmitter receptors did not reduce the effect of acoustic trauma, and the acoustic trauma used herein affected structures involved in transduction before it affected the postsynaptic structures. We speculate that the active process is affected first during acoustic trauma. This interpretation is consistent with the notion that stereocilia are structures that make up part of the active process.