Genes Help Determine Brain Response to Alcohol, Medication, NIAAA Says

Alcohol consumption prompts the brain to release the pleasure chemical dopamine, but genes may influence the degree to which the brain responds to drinking and — by extension — how effective medications like naltrexone are in treating alcoholism.

Researchers at the National Institute on Alcohol Abuse and Alcoholism (NIAAA) found that genetic variations in the mu-opioid receptor sites in the brain’s reward system seem to influence the release of the neurotransmitter dopamine and the degree of pleasure that individuals get from drinking.

Researchers also found that naltrexone — a drug that works to block the release of dopamine resulting from drinking — was more effective for patients with some genetic profiles than others.

“Our data strongly support a causal role of the 118G variant of the mu-opioid receptor to confer a more vigorous dopamine response to alcohol in the ventral striatum,” said NIAAA researcher Vijay A. Ramchandani, Ph.D. “The findings add further support to the notion that individuals who possess this receptor variant may experience enhanced pleasurable effects from alcohol that could increase their risk for developing alcohol abuse and dependence. It may also explain why these individuals, once addicted, benefit more from treatment with blockers of endogenous opioids.”

Markus Heilig, NIAAA’s clinical director, noted that naltrexone also worked better in the early stages of alcoholism, when the body still believes it is being rewarded for drinking (’reward craving’). At a certain point, however, the brain switches to a pattern called ’relief craving’ — what Heilig called a “pathological pattern of anxiety” — where naltrexone isn’t nearly as helpful.

The latest findings were published online in the journal Molecular Psychiatry.