Long-term effects of preoptic area knife cuts on the maternal behavior of postpartum rats.

Knife cuts severing the lateral connections of the medial preoptic area disrupt maternal behavior in postpartum rats. In these studies the knife cuts were produced 1-2 days prior to behavioral testing. The present study examined whether preoptic area knife cuts produce long-term deficits in maternal behavior. Nulliparous Charles River CD rats received knife cuts severing the lateral connections of the medial preoptic area or sham cuts. Approximately 2 weeks later they were mated. All females delivered young 22-23 days after mating, and litter size did not differ between the groups. Females with preoptic knife cuts cleaned their young, built nests (albeit of inferior quality), crouched over their young in a nursing posture, and lactated. The major deficit shown was the near total elimination of retrieval behavior. Females with preoptic knife cuts, however, were capable of performing the oral-motor responses associated with hoarding behavior. These results show that severing the lateral connections of the medial preoptic area does produce long-term deficits in maternal behavior, particularly with respect to maternal retrieving.