ASA 125th Meeting Ottawa 1993 May

4aPP13. Enhancement of cochlear signal cell and CM responses after exposure to an intense tone or noise.

Bradley W. Pietras

Jozef J. Zwislocki

Inst. for Sensory Res., Syracuse Univ., Syracuse, NY 13244-5290

The phenomenon of decreased cochlear sensitivity after exposure to intense noise is well known. It predominantly affects low levels of stimulation and, when not too severe, it usually exhibits sensitivity recruitment at higher levels. By contrast, in Mongolian gerbils, enhanced receptor potentials of outer hair cells have been found, as studied through intracellular recording from Hensen's cells. According to previous studies, alternating potentials of the latter faithfully reflect those of the former. The enhancement affected mainly high levels of stimulation, and was practically absent in low level responses. It did not seem to affect the shapes of Hensen's cells' transfer functions. It was present at the cochlear location of 2 kHz BF after exposure to either a 1-kHz tone or a broadband noise, both at 100 dB SPL. It increased over exposure durations as long as 60 to 90 min and decreased slowly after exposure termination. The enhancement did not appear to be correlated with fluctuations in Hensen's cell resting potentials or the endolymphatic potential. It was weak when measured in CM. [Work supported by NIDCD.]