Prolonged exposure to odors in the rat: effects on odor detection and on mitral cells

Abstract

Rats were raised from four to seventy days of age in ethylacetoacetate (EA), 4-methylvaleric acid (MV), or clean air (CA) vapor. Half of the animals in each group were sacrificed immediately upon removal from the exposure cages and the remaining animals were housed in a vivarium, placed on a water deprivation schedule and trained to detect EA and MV odors prior to sacrifice. The only behavioral deficit observed was in the slower acquisition of the MV odor detection task for rats which were raised in MV vapor and were tested first on that vapor. Inspection of selected 10μm thick Nissl-stained sections of olfactory bulbs revealed no differences in intensity of staining, size of mitral cells or number of mitral cells between immediately sacrificed and later sacrificed animals, or among the exposure groups. These results are in agreement with reports that prolonged exposure to individual odors may be largely without effect on the ability to detect that odor, but they fail to confirm earlier findings of dense degeneration in selected areas of the mitral cell layer after prolonged odor exposure.