RECOVERY OF OLFACTORY BEHAVIOR .1. RECOVERY AFTER A COMPLETE OLFACTORY-BULB LESION CORRELATES WITH PATTERNS OF OLFACTORY NERVE PENETRATION

The olfactory system is an excellent system in which to study issues r elated to potential functional recovery after a debilitating brain inj ury. The olfactory system is well-characterized, easily accessible and there are a vast number of studies available from a variety of perspe ctives. The experimental aim of this research is to examine the anatom ical correlates associated with potential behavioral recovery in rats that receive complete olfactory bulb lesions as neonates or as adults. The results show that behavioral recovery occurs only when olfactory nerve penetration of the central nervous system is observed. Further, both olfactory nerve penetration and behavioral recovery are age-depen dent phenomena. The olfactory nerve penetration only occurs when the o lfactory bulb lesion is performed in neonates. Behavioral recovery of olfactory ability follows a linear trend and reaches near normal level s during the six week behavioral testing period. Histological analysis using an antibody for olfactory marker protein (an olfactory nerve-sp ecific marker) reveals two potential candidates for the anatomical pat hway responsible for behavioral recovery: olfactory nerve to orbital f rontal cortex and olfactory nerve to olfactory peduncle. This report p resents evidence that recovery of olfactory ability can occur in the a bsence of the olfactory bulb if the lesion is performed when the rat i s still a neonate.