Noise-induced vasoconstriction in the cochlea.

Observation of the inner ear vessel using the casting method has the advantage of revealing the whole of the blood vessel in the one animal. This study was employed the blood vessel casting method and stylene cracking method to observe the morphological changes occurring in the inner ear vessel due to sound exposure. Results indicated vasoconstriction of the blood vessels of the cochlear lateral wall and spiral lamina due to sound exposure. Sludging of the blood cells was also recognized in these blood vessels. Such morphological changes were found to be reversible. The above findings thus imply that the cause of NITTS (Noise-Induced Temporary Threshold Shift) and NIPTS (Noise-Induced Permanent Threshold Shift) lies in impaired blood flow due to vasoconstriction of the inner ear capillary.