Comparing cocaine’s effects on rats who have given birth to rats who haven’t has shown differences in brain chemistry and behaviour.

“Mother” rats’ brains released less of the chemical dopamine, which helps cause the “high” from cocaine. Researchers also found an interaction with stress: mother rats that were exposed to periods of increased stress weren’t willing to work as hard to get a dose of cocaine.

Taken together, the findings suggest that the experience of becoming a mother alters a female’s overall response to cocaine – adding complexity to the issue of how best to treat addiction.