Early unilateral deprivation modifies olfactory bulb function.

Unilateral olfactory deprivation during postnatal development produces significant structural and neurochemical modifications of the olfactory bulb. In the present report, we describe the functional consequences of such deprivation. Rat pups had a single naris occluded on postnatal day 2 (PN2) to deprive them of early olfactory stimulation. On PN20-22, the occluded naris was reopened, the previously open naris was sealed, and responses of the deprived olfactory bulb to odors were assessed using both single-unit recording from mitral/tufted cells and quantitative 14C-2-deoxyglucose (2-DG) autoradiography. While the response properties of individual odor-stimulated mitral/tufted cells were not altered by early deprivation, spontaneous activity was depressed, and there was a significantly higher incidence of odor-responsive mitral/tufted cells in deprived compared to nondeprived bulbs. In addition, odor-stimulated deprived bulbs demonstrated greater uptake of 2-DG than did non-deprived bulbs. Together, these data indicate that the olfactory system demonstrates an increased responsiveness to sensory cues following early deprivation.