[Cholinergic innervation of the outer hair cells. Possible significance for loss of discrimination in sensorineural hearing loss].

Cochlear outer hair cells (OHC) are capable of auditory perception. In addition, they influence actively the micromechanics of the cochlea. This concept is based on the observation of motile responses induced by electrical and chemical stimuli. OHC motility is probably controlled by the efferent olivo-cochlear system. By means of two monoclonal antibodies against intra- and extracellular epitopes of ACh-receptors a transmembraneous receptor molecule was visualized in the OHC membrane. Besides morphological studies functional investigations using acetylcholine and its analogues were carried out. We observed contractile responses of OHCs that were reversible and dependent on the applied transmitter concentration. We suggest that the high frequency selectivity and sensitivity of the cochlea is modulated by the efferent innervation and the observed ACh-induced OHC motility.