Temporary threshold shift due to noise exposure in guinea pigs under emotional stress.

One of the factors which can affect the amount of temporary threshold shift (TTS) due to acoustic overstimulation is known to be the general metabolic state of the exposed subject. The present study was conducted to elucidate how preexisting intense emotional stress in awake guinea pigs could influence the TTS induced by exposure of 4 kHz at 120 dB SPL for 20 min. Considering the hypersympathetic activity in both 'stress' and 'noise' it was assumed that the two factors would act synergetically on the cochlear function. However, an unexpected result was obtained. The mean threshold for the stressed animals following noise exposure was significantly lower (better) than that of the controlled, sedated, guinea pigs.