Outer hair cells do produce the preponderance of receptor potentials

Abstract

Numerous experiments [e.g., Davis et al., Laryngoscope (1958); Dallos and Wang, Audiology (1974)] in which outer hair cell damage is accompanied by good preservation of inner hair cells, have indicated that, in such cochleas, the CM is suppressed by 30–40 dB. The conclusion drawn from such results was that outer hair cells generate a very large fraction of the recorded CM, and that in fact in a normal cochlea the CM is determined by the output of the outer hair cells. While these experiments are very suggestive, a direct confirmation of the dominant role of outer hair cells in CM production has been lacking. What is required for such confirmation is recording from cochlear regions that are denuded of inner hair cells. We are now reporting on such experiments. With very massive doses of kanamycin one can achieve a pattern of hair cell degeneration in the guinea pig's cochlea, whereby only outer hair cells remain in the fourth (apical) turn, and whatever inner hair cells are preserved are confined to more basal regions. Recordings of CM and SP from the scalar media of the fourth turn of such cochleas is compared to data from normal preparations. While many animals are seen to have severely depressed responses, several possess essentially normal receptor potentials. This finding tends to confirm the suggestion that outer hair cells are the primary source of the cochlear receptor potentials; both CM and SP. [Supported by grants from the NINCDS.]