THE D2 ANTAGONIST SPIPERONE MIMICS THE EFFECTS OF OLFACTORY DEPRIVATION ON MITRAL TUFTED CELL ODOR RESPONSE PATTERNS/

Wistar rats had a single nare occluded on postnatal day 30, depriving the ipsilateral olfactory bulb of odor stimulation. The deprivation la sted for either 1-2 months (short-term) or 12 months (long-term). As p reviously reported, deprivation greatly reduced tyrosine hydroxylase i mmunoreactivity (the rate limiting enzyme for dopamine synthesis) in t he glomerular layer of the ipsilateral olfactory bulb. The nare was th en reopened and odor response patterns of mitral/tufted cells were exa mined. The proportion of mitral/tufted cell single-units responding to a single odor was enhanced by deprivation. Furthermore, the proportio n of mitral/tufted cells responding to more than one odor was increase d by deprivation, suggesting a decrease in discrimination. Finally, in undeprived bulbs, the dopamine D-2 receptor antagonist spiperone mimi cked the effects of deprivation on mitral/tufted cell odor response pa tterns. The results are interpreted as an activity-dependent dopamine modulation of lateral and feedback inhibition in the olfactory bulb, a nd are compared with similar events in the dark-adapted retina.