[Effect of impulse noise exposure on the endocochlear potentials].

Effects of impulse noise exposure (25 impulses, peak level 165 dB SPL) on endocochlear potentials (EP) and CAP threshold were investigated in guinea pigs. Eight hours after exposure, EP recorded from the second turn of the cochlea was very low (19.0 +/- 1.7 mV) and the negative EP resulted from prolonged anoxia was markedly diminished (-EPmax = -6.4 +/- 1.3 mV). The return rate of EP after reventilation was also reduced. The positive EP returned to normal values 7 days after exposure but the negative EP and the CAP threshold did not. The results suggest that the stria vascularis was also damaged together with the organ of Corti, the degree of damage seemed to be heavier in the latter if only complete recovery of positive EP is taken into consideration. The stria vascularis was also not completely restored when examining the return rate of EP after reventilation. Mechanisms underlying the changes in EP and hearing sensitivity after noise exposure are discussed.