Experimental hypercholesterolemia and auditory function in the chinchilla

Possible harmful effects of a high-cholesterol diet on auditory function were suggested by our previous work in rabbits, in which evoked potentials were measured from a chronic electrode inserted into the inferior colliculus. However, serum cholesterol levels in those rabbits tended to be extraordinarily high, i.e., more than 1,500 mg/dL. Chinchillas were used in the present work as an animal model to study the relationship between hypercholesterolemia and auditory dysfunction. One percent cholesterol in standard Chinchow was fed to chinchillas for three months. The experimental groups showed a high mean cholesterol level of 437 +/- 394 mg/dL (N = 9). Isopotential curve of the cochlear microphonics, threshold of action potentials (AP), and endocochlear DC potential did not differ from those in the control group. When moderately intense sound (12 kHz, 95 dB SPL) was given for ten minutes, however, the reduction in AP threshold was significantly greater (P = .036) in the cholesterol group. It is postulated that hypercholesterolemia may be one of the factors involved in differential susceptibility to noise.