PATHOLOGY OF THE COCHLEA FOLLOWING A SPONTANEOUS MUTATION IN DBA 2 MICE/

The DBA/2 strain of mice usually presents with noise-induced epileptic seizures and hearing disorders. After a spontaneous mutation a strain with early hearing loss and circling behaviour was produced. This str ain presents with clinical symptoms found in diseases connected to inn er ear disorders. These animals do not suffer from periodical disorder s, however, but have functional disturbances continuously and can ther efore serve as an animal model for diseases originating from both part s of the inner ear. The genetic inheritance appears to be autosomal re cessive. Offspring showed circling behaviour and severe pathology in t he vestibular part of the inner ear. In the present study pathology of the cochlear part of the inner ear was visualized using conventional microscopical techniques. The content of actin and fodrin was labelled immunohistochemically, and hearing was assessed with auditory brainst em recordings. After 1 month the animals showed deterioration of the c ochlear part of the inner ear. At 6 months no organ of Corti remained and the animals were deaf. Transmission and scanning electron microsco py revealed severe apical hair cell changes. The content of a-actinin and fodrin in the DBA/2 mouse was already fainter than that in age-mat ched CBA control mice at the age of 1 month. Labelling of antibodies a gainst fodrin increased in the supporting cells of the older animals, probably owing to the replacement of hair cells.