MATERNAL AGGRESSION IN RATS - EFFECTS OF OLFACTORY BULBECTOMY, ZNSO4-INDUCED ANOSMIA, AND VOMERONASAL ORGAN REMOVAL

Previous studies from our laboratory indicate that somatosensory input s to the snout and ventral trunk, but not visual or auditory stimuli, play critical roles in the elicitation and maintenance of maternal agg ression by lactating Norway rats toward a strange male intruder. There are conflicting reports on the influence of olfaction on maternal agg ression. We explored the possible roles of central or peripheral anosm ia on maternal aggression in Long-Evans rats during early lactation. I n Experiment 1, responsiveness to both volatile and non-volatile odors was eliminated by bilateral olfactory bulbectomy (BOB), carried out d uring mid-gestation. BOB resulted in a reduced likelihood and intensit y of maternal aggression on days 1 and 5 of lactation (L1 and L5), but also severe deficiencies in maternal behavior and litter growth and s urvival. In Experiment 2, anosmia to volatile odors was induced by spr aying zinc sulfate intranasally on gestation day 21 and L1. This treat ment had little or no effect on maternal aggression on L1 of L2 or on maternal behavior, especially if there was a 1-day recovery between th e second treatment and testing. In Experiment 3, responsiveness to non -volatile odors was eliminated by vomeronasal-organ removal (VNX) carr ied out prior to mating. VNX did not disturb maternal behavior on L2-L 8 or maternal aggression on L1 or L5. These results and others suggest that the expression of maternal aggression is affected by volatile od ors, mediated possibly by accessory chemosensory systems such as the s eptal organ, or by neural changes that follow olfactory deafferentatio n, or both. (C) 1995 Academic Press, Inc.