ABOLITION OF THE RECEPTOR POTENTIAL RESPONSE OF ISOLATED MAMMALIAN OUTER HAIR-CELLS BY HAIR-BUNDLE TREATMENT WITH ELASTASE - A TEST OF THE TIP-LINK HYPOTHESIS

To test the hypothesis that the tip-links of hair-cell stereocilia are essential for mechanoelectrical transduction, tip-links of isolated o uter hair cells (OHCs) of the guinea-pig cochlea were eliminated with a proteolytic enzyme, elastase, and the influence on the receptor pote ntial measured with the whole-cell patch-clamp technique. Within 45 s of immersion of the hair bundle in 20 IU/ml elastase, the receptor pot ential in response to direct deflection of the hair bundle was irrever sibly abolished. The electrical input impedance of the cell remained u nchanged, implying that the channels of the basolateral membrane were not affected by elastase. The effect of elastase on the receptor poten tial was comparable to changes seen after mechanically induced hair-bu ndle damage. As a further control, a putative transduction-channel blo cker, dihydrostreptomycin (68 mu M), which does not affect tip-links, was applied to the hair bundle. Although the receptor potential was al so blocked by dihydrostreptomycin, the effect was reversible. The resu lts suggest that tip-links are required for mechanoelectrical transduc tion of mammalian OHCs.