Prolonged odor exposure causes severe cell shrinkage in the adult rat olfactory bulb.

Adult sensory systems generally remain viable as long as stimulation or disease do not physically damage the sensors. Continuous exposure of adult rats to a single odor for two months, however, caused a shrinkage of mitral cells in the olfactory bulb which was more extensive and severe than found in adult rats exposed to deodorized air, or normal rat colony odors. The results suggest that lack of excitation of mitral cells may cause significant shrinkage (deodorized air treatment), but more severe shrinkage may occur through inhibition or masking by a single dominant odor in the environment. These results have implications for humans living or working in odorous environments.