Mom’s past drug abuse may alter brain chemistry of offspring

SAN DIEGO — Drug-using moms-to-be who quit before pregnancy starts can still raise the risk among both their children and grandchildren for addiction or other psychiatric disorders, a new study in rats suggests.

Researchers at the Tufts University Cummings School of Veterinary Medicine in North Grafton, Mass., exposed female rats to morphine for 10 days during adolescence. After three weeks drug-free, the rats mated with healthy males. Male offspring of those matings produced less of a molecule sensitive to the chemical messenger dopamine in the nucleus accumbens, a brain structure related to addiction and reward-seeking behavior. A similar deficit was found in male grandchildren of the original rats, Elizabeth Byrnes of Tufts reported November 14 at the annual meeting of the Society for Neuroscience.

Problems with the brain’s dopamine system have been linked to substance abuse and mental illness.

Exposing the affected offspring to a chemical that mimics dopamine induced elevated secretion of a stress hormone, suggesting that the rats’ stress control systems had been impaired.

Byrnes said research is continuing to determine how the effects are transmitted from generation to generation, presumably by some epigenetic mechanism that influences the expression of genes — their activity in producing proteins — without altering the genes themselves.

“We’re seeing changes in gene expression in an area of the brain critical to reward-related behavior, including drug use,” Byrnes said. “Adolescent opiate use could in fact trigger these multigenerational changes that may make these offspring more vulnerable to drug addiction and other dopamine-related, reward-related disturbances.”