[The effects of auditory research on clinical practice]

Recent research has shown that only the inner hair cells pass information on to the brain while the outer hair cells serve as an active amplifier and thus stimulate the inner cells. The electromotility of the outer hair cells is very vulnerable. If it is lacking, sensorineuronal hearing loss occurs. Substances, that compete for the chloride combining site of the motor protein prestin, such as salicylate, might have a blocking effect on the regulation of electromotility. On the other hand, the control of the intracellular Ca(2+) level and the intracellular combination of ions in the outer hair cells might protect their electromotile properties against damage caused by harmful substances (ototoxic drugs) or mechanisms (exposition to noise), which would otherwise lead to irreversible sensorineuronal hearing loss. This is because an increase in the intracellular Ca(2+) level activates phosphorylating enzymes. Thus the stiffness of the outer hair cells is reduced, causing an increase in electromotility.