DECLINE AND RECOVERY OF OLFACTORY RECEPTOR EXPRESSION FOLLOWING UNILATERAL BULBECTOMY

The effects of unilateral olfactory bulb ablation upon the odorant rec eptor expression were studied during the degeneration/regeneration pro cess in the olfactory epi thelium of adult rats. Using the in situ hyb ridization approach, we compared the time course of decay and recovery of expression for three different receptor subtypes (OR14, OR5, OR124 ). The number of neurons expressing receptor subtypes dramatically dec reased in the olfactory epithelium on the lesioned side and reached a minimum at day 5 postsurgery. A progressive recovery was then observed from day 5 to day 15 postlesion, when a plateau was reached. Noticeab le differences in the recovery level of receptor expression were obser ved according to the zonal patterning: the recovery level for neurons located in the lateral zone reached 70% of the control side value whil e the recovery levels in the dorsal and medial zones represented 35% a nd 53% of this value, respectively. Axotomy experiments suggest that z one-specific differences in receptor reexpression reported after bulbe ctomy might be related to the trophic influence of the olfactory bulb.