Some Vascular Effects of Noise Exposure in the Chinchilla Cochlea

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Abstract
Chinchillas were exposed to pink noise at levels ranging from 110 dB (for 8 hours) to 125 dB (for 15 min). After a 3-week survival period, the animals were killed and cochlear tissues were prepared using a soft-surface preparation technique. To evaluate discrete changes of the cochlear vasculature and minimize bias with respect to what was judged pathological, a method was used whereby experimental and control animals were mixed and randomly assessed without prior knowledge of the group to which the specimen belonged. The results were analysed by computer. Cochlear hair cell damage was slight. Statistically significant differences in the vasculature between noise-exposed and control animals were few. For example, in some cochlear vessels in the experimental animals, red blood cells were found to be less frequent; other vessels showed an increase or decrease in endothelial or periendothelial cells. A more prominent difference between control and noise-exposed animals was an increased variability in several of the adopted vascular parameters, thus disturbing the normal regular pattern and appearance of the vascular bed. This was especially evident with respect to the frequency and spacing of red blood cells in the vessel lumen. Contrarily, some parameters previously considered to be typical examples of vascular degeneration such as avascular channels and perivascular spaces were found equally often in noise-exposed and control animals. Some possible explanations regarding the observed vascular changes are discussed.