Cochlear blood flow in noise-damaged ears.

Cochlear blood flow was measured in rats with a known noise-induced hearing loss, using the microsphere technique. The animals were exposed to simulated industrial noise for 3 months. The rats were divided into four groups: young and old; normotensive (N) and spontaneously hypertensive (SH). The mean values of the cochlear blood flows were compared with those of rats from matched groups not exposed to noise. The mean cochlear blood flow in the noise-exposed groups was lower than in the non-exposed groups. The decrease in cochlear blood flow was significant for all groups except young SH rats and was more pronounced in the older age group. Cochleas from the groups of old N and SH rats were investigated in the scanning electron microscope. Extensive changes were far more common in SH than in N rats.