Effect of cocaine sensitization prior to pregnancy on maternal care and aggression in the rat

Although many studies have investigated the effects of gestational and lactational cocaine use on maternal behavior, few studies have examined the effects of prior adult cocaine use on maternal behavior.

In the current study, intraperitoneal cocaine or saline was administered to adult female rats for 10 days, treatments were stopped for 4 days, and the females were then mated. Litter size and weight were recorded on days 2 and 16 of lactation, and maternal care, maternal aggression, and light/dark box activity were assessed on days 2, 9, and 16 of lactation.

The cocaine-treated females exhibited behavioral sensitization on treatment day 10. Mothers previously treated with cocaine retrieved pups more quickly, spent more time caring for the pups (increased pup retrieval, pup grooming, and crouching over the pups by the mother), and were more aggressive towards a male intruder compared to saline-treated control animals on day 2 of lactation. These effects were specific to maternal behavior, as other behaviors were mostly unaffected by prior cocaine treatment. Data from light/dark box tests indicate that cocaine did not affect activity in this test. There were few significant behavioral effects of prior cocaine treatment on lactation days 9 and 16.

Prior cocaine use may have lasting effects on offspring care and maternal aggression, specifically during early lactation. The present data support the hypothesis that maternal behavior is increased by prior cocaine sensitization, possibly due to cross-sensitization between cocaine and the natural reward of maternal behavior.