Immediate noise effects on cochlear vasculature in the guinea pig.

Nine guinea pigs were exposed to a 4 kHz narrow band noise at 120 dB for 30 minutes. The animals were killed immediately following exposure and the cochlear tissues prepared using a soft-surface preparation technique. Experimental and control animals were mixed and randomly assessed without prior knowledge of the groups of which the specimens belonged. The results were analysed by computer. Statistically significant differences in the vasculature between noise-exposed and control animals of a general nature included: more changes in spiral lamina than external wall vessels, more changes in vessels facing perilymph than endolymph, and more changes apically than basally. Results indicate slight intracochlear compensations in blood flow, that could potentially maintain a more constant circulation in regions of the cochlea corresponding to the 4 kHz narrow band exposure noise. Methodological aspects of our inner ear vascular technique as well as some hypothetical explanations regarding the observed changes in the blood supply are discussed.