Prenatal cocaine alters later responses to morphine in adult male mice

Mice prenatally exposed to cocaine (25 mg/kg), physiological saline or non-treated during the last 6 days of pregnancy were evaluated as adults for the rewarding properties of 2 mg/kg of morphine, using the conditioned place preference (CPP) procedure. Likewise, isolated animals underwent a social interaction test with conspecifics after receiving the same morphine dose. Unlike control or animals pre-treated with saline, subjects prenatally treated with cocaine did not develop CPP with this dose of morphine. Only cocaine-exposed animals showed increased threat, avoidance and fleeing during the social encounter. No differences in motor effects of morphine were observed. Analysis of monoamines revealed effects of housing conditions, isolated animals having fewer DOPAC but higher levels of HVA than those grouped, but in both groups there was a decrease in DOPAC in cocaine- and saline-treated mice. Prenatal cocaine exposure decreases the response to the rewarding properties of drugs in mature offspring. They also implicate cocaine consumption during pregnancy could affect the response of offspring to take other drugs of abuse.