Noise effects on the cochlear vasculature in normotensive and spontaneously hypertensive rats

The cochlear vessels and the distribution of red blood corpuscles were studied in normotensive (N) and spontaneously hypertensive (SH) rats with and without noise exposure. The evaluation was made in a double blind manner. Ten N-rats and ten SH-rats were exposed to noise for 8 weeks and terminated immediately thereafter. The noise consisted of a 2 kHz broad noise band swept from 3 kHz to 30 kHz with a resultant equivalent sound level of 100 dB (lin) 10 h. Seven of 84 vascular parameters differed statistically at the 1% level between N- and SH-rats, and 8 and 10 parameters respectively differed for N- and SH-rats as a result of noise exposure. The observations were interpreted as indicative of a precapillary sphincter constriction in the radiating arterioles of the external wall with an upstream relative stasis and a downstream relative lack of blood, both in N- and SH-rats. In the spiral lamina the observations were interpreted as signs of a decreased blood flow after noise exposure, both in the N- and SH-animals, and most marked in the SH-animals after noise.