VESTIBULAR MORPHOLOGY IN RELATION TO AGE AND CIRCLING BEHAVIOR

The DBA/2 strain of mice have genetically induced vestibular dysfuncti on that presents grossly at an early age as circling behavior and abno rmal righting reflexes. The vestibular morphology of this strain has n ot previously been examined. DBA/2 mice of different ages that showed circling behavior were sacrificed and then had their inner ears immedi ately removed and fixed in glutaraldehyde. The specimens were prepared for light, transmission and scanning electron microscopy. Additional specimens at 10 months of age were fixed with paraformaldehyde for imm unohistochemical investigation and labelling of alpha-actinin. Non-cir cling litter males served as controls. The morphology and immunohistoc hemistry of the vestibular end-organs were evaluated as a function of age and circling behavior. The sensory epithelium of the ampulla and u tricle in the circling mice showed softening of the cuticle, hair cell cytoplasmic herniation, expelled cellular debris, fused stereocilia a nd giant hair cells that progressively increased in severity with age. The non-circling litter mates showed similar but less severe patholog y of the vestibular sensory epithelium. The immunohistochemical analys is showed no differences at a magnification of 400 x.