EFFECTS OF UNILATERAL OLFACTORY DEPRIVATION IN THE DEVELOPING OPOSSUM, MONODELPHIS-DOMESTICA

Unilateral naris closure in young rodents leads to striking alteration s in the development of the ipsilateral olfactory system, One of the m ost pronounced effects is a 25% reduction in the size of the experimen tal olfactory bulb, a change that stems in part from decreased cell su rvival. Since naris occlusion in rodents alters the system more during development than in adulthood, me investigated the consequences of ol factory deprivation in a species that is born in a very immature state , Monodelphis domestica. In this pouchless marsupial, offspring are bo rn after a short 14-day gestation. In the present study, the thymidine analogue bromodeoxyuridine was used to examine early postnatal neurog enesis in the olfactory bulb, Unlike rats and mice, neurogenesis of th e main output neurons (the mitral cells) continues into postnatal life , Unilateral naris closure was begun on postnatal day 4 (P4) or P5 in monodelphis and continued for 30 or 60 days, Laminar volume measuremen ts revealed a significant reduction in the size of the experimental bu lb following 60, but not 30, days of early olfactory deprivation. Mitr al cell number estimates indicated a significant reduction after both 30 and 60 days of naris closure. The immaturity of Monodelphis offspri ng may render the population of mitral cells susceptible to the effect s of olfactory deprivation, These findings suggest that afferent activ ity plays a role in the survival of all bulb neurons, irrespective of cell class. (C) 1997 John Wiley & Sons, Inc.