Suckling stimulation modulates the maintenance of postpartum aggression in mice.

Previous work in female mice has shown that suckling stimulation is essential for the initiation of male-directed aggression during the immediate postpartum period. The present work examined the importance of this stimulus for the maintenance of aggression during lactation. Surgical excision of nipples (thelectomy) on Postpartum Day 5 accelerates the decline in aggression that ordinarily occurs during the final third of lactation (Postpartum Days 15-21), but does not disrupt the behavior during the middle third of lactation (Postpartum Days 6-12). Thus, both the initiation of aggression during the early postpartum period and the maintenance of the behavior during late lactation are controlled by suckling from young.