Vestibular pathology in a new-mutant mouse.

The histological characteristics of the vestibule in a strain of new-mutant mice were studied under light microscopy. These new-mutant mice, manifesting drawing back, circling, head-tossing and hyperactive behavior arose as a spontaneous mutation in the C3H/He stock. For our study, 36 of these mice ranging in age from 10 days to 18 months were used. At 10 to 15 days after birth, the vestibular gross anatomy was well-developed and all three cristae and two maculae were morphologically normal. Age-dependent degeneration of the saccular maculae was found to begin at 21 days, and almost all hair cells were missing at 90 days. Further, morphological changes in the utricular maculae appeared at one year, and a severe loss of hair cells was observed at 18 months. In contrast, the cristae ampullaris remained well preserved until the age of 18 months. The phenotype of the abnormal gene in these mutant mice correlates to the morphological abnormalities seen in the vestibule.