EARLY OLFACTORY ENRICHMENT AND DEPRIVATION BOTH DECREASE BETA-ADRENERGIC-RECEPTOR DENSITY IN THE MAIN OLFACTORY-BULB OF THE RAT

The density of noradrenergic locus coeruleus projections and beta-adre nergic receptors in the main olfactory bulb of the rat increases with age. Both beta(1)- and beta(2)-adrenergic receptor subtypes exhibit la minar distributions, with focal regions of high receptor density prese nt within the neuropil of individual glomeruli. Since the first synapt ic contacts between olfactory receptor neurons and bulbar neurons occu r within the glomeruli, early olfactory experiences possibly could inf luence the density or distribution of beta-adrenergic receptors in the bulb. We therefore investigated the effects of olfactory deprivation and early olfactory enrichment on the density and distribution of beta -adrenergic receptors in the main olfactory bulb. Animals were subject ed to either unilateral naris closure on postnatal day 1 or odor train ing from postnatal days 1-18. Bulbs were removed on postnatal day 19 a nd subjected to quantitative autoradiography using the beta-adrenergic receptor antagonist [I-125]iodopindolol and specific receptor subtype antagonists ICI 118,551 (beta(2)-antagonist) and ICI 89,406 (beta(1)- antagonist). Unilateral naris occlusion decreased both the number of b eta(2) glomerular foci and the density of beta(1) and beta(2) receptor s in the deprived bulb compared to the nondeprived bulb. Early odor tr aining resulted in a significant decrease in the number, area, and rec eptor density of beta(2) glomerular foci in the midlateral region of t he bulb. The distribution of beta(2) glomerular foci also differs with these two sensory manipulations. Changes in beta-adrenergic receptor density in response to both early learning and olfactory deprivation m ay be induced by a transient increase in olfactory bulb norepinephrine . (C) 1995 Wiley-Liss, Inc.