Protective value of sympathectomy of the ear in noise.

Noise-induced hearing loss was assessed in unilaterally sympathectomized rats exposed one month to 100 dB Leq(lin) noise. The systolic blood pressure of these animals was in the range of 110-140 mmHg. Auditory sensitivity was determined electrophysiologically by brainstem response audiometry to 1/3-octave filtered clicks. The results showed that the loss of sensitivity was about 10 dB smaller (p less than 0.01) on the sympathectomized side. This observation may partially explain the individual differences in susceptibility to noise-induced hearing loss and point towards protective measures and therapeutic possibilities through manipulation of sympathetic activity in the inner ear.