Cochlear hair cell and vascular changes in the guinea pig following high level pure-tone exposures

Noise is thought to exert metabolic and/or mechanical stress on sensory and vascular tissues of the cochlea, the relative influence of the stressors being influenced by the intensity of the noise. Guinea pigs exposed to either of two pure-tone frequencies, 1.33 or 3.85 kHz for 6 hours at intensity levels ranging from 102 dB to 120 dB SPL, were studied for pathological changes in two spiral lamina vessels--the vessel of the basilar membrane (VSBM) and the vessel of the tympanic lip (VSTL). In general, animals sustaining mild to severe degrees of hair cell destruction one month after noise exposure showed little vascular change in the vessels studied. With respect to the vasculature, the concept of a 'critical level' seems to be dependent on exposure frequency, in that only above 117 dB SPL at 3.85 kHz was there any change in the pattern of damage to the spiral lamina vessels.