Being a mother changes cocaine impact

There are differences in how intensely the "pleasure centers" in mother rats' brains react to cocaine compared with non-mothers, U.S. researchers say. Postdoctoral research fellow Jennifer Cummings and Jill Becker, a professor of psychology and psychiatry, both at the University of Michigan, said the brains of the mother rats released less of the chemical dopamine, which helps cause the "high" from cocaine. They also found an interaction with stress: Mother rats exposed to periods of increased stress weren't willing to work as hard to get a dose of cocaine, compared with rats that had never given birth or mother rats that weren't exposed to the stress -- even though the stressed mother rats showed an increased tendency to use cocaine when it was easy to get. Taken together, the findings suggest the experience of becoming a mother alters a female's overall response to cocaine, the researchers said. "While we have not yet identified a mechanism to explain these differences, they do suggest that the reward system and brain circuitry affected by cocaine is changed with maternal experience," Cummings said in a statement. The findings were presented at the Society for Neuroscience meeting in New Orleans.