Abstract

Maternal aggression toward intruders is temporarily expressed during lactation in association with the rearing and protection of offspring to promote their survival and growth. This normal component of maternal behaviour that requires both the hormonal changes occur at the end of pregnancy and due to the presence of newborn for its establishment analyzed in Wistar rats. The effects of nitric oxide (NO) by L-arginine (L-arg) was analyzed when administered on days 1, 4, and 8 postpartum in order to observe the maternal aggressive response to an intruder. Data collected indicated that L-arg treated dams exhibited a significant increase of the frequency of biting on postpartum days 1 and 8.   In contrast, findings also showed reductions of the frequency of sniffing on day 1. Both frontal and lateral attacks also showed significant decreases attributable to L-arg treatment. These findings suggest that the role of NO during the lactating period may be relevant for the survival and long-term behavioral development of the progeny due to the fact that it has been demonstrated that several neurotransmitters are closely regulated by NO. Therefore, this is interesting in the development of antidepressant drugs for possible human applications.

Key words: Aggressive behavior, lactating period, rats, L-arginine treatment, postpartum.