DEVELOPMENT OF OLFACTORY MARKER PROTEIN AND N-CAM EXPRESSION IN CHEMOSENSORY SYSTEMS OF THE OPOSSUM, MONODELPHIS-DOMESTICA

Using olfactory marker protein (OMP) and neural cell adhesion molecule (N-CAM) immunohistochemistry, the present study describes development of olfactory and vomeronasal systems in pre-and postnatal opossums, M onodelphis domestica. As revealed by OMP expression, development of th e main olfactory system precedes that of the vomeronasal system by 1-2 weeks. OMP is expressed throughout (homogeneously) the nerve and glom erular layers of the main (MOB) but is expressed more strongly (hetero geneously) in the anterior as compared to the posterior accessory (AGE ) olfactory bulb. N-CAM expression is homogeneous in both MOB and AOB. The heterogeneity in the AOB is developmentally regulated, since in t he 30-day-old AOB the expression of OMP is homogeneous, becoming heter ogeneous during the second month of life. Maximal expression of N-CAM precedes maximal expression of OMP in the VNS by about 2 weeks. From 7 to 21 days of age only, there is a small population of OMP-positive, N-CAM-negative olfactory and vomeronasal axon terminals that penetrate deep into the brain parenchyma, overgrowing their normal targets in t he MOB and AOB, respectively. (C) 1997 Wiley-Liss, Inc.