Pot Plus Alcohol Kills Young Rats' Brain Cells

April 23 -- TUESDAY, April 22 (HealthDay News) -- A combination of THC, the main psychoactive ingredient in marijuana, and mildly intoxicating doses of alcohol caused widespread nerve cell death in the brains of young rats, a German study finds.

Researchers from Humboldt University, Berlin, administered THC, a synthetic form of THC, ethanol, an anticonvulsant called MK-801, and phenobarbital to rats between one and 14 days old. A previous study by the same team found that ethanol and drugs such as sedatives, anesthetics and anticonvulsants caused extensive nerve cell death in the brains of young rodents. The new study was conducted to determine if cannabinoids caused similar harm.

The researchers found that THC and synthetic THC did not cause nerve cell death when administered alone but did cause cell death when given with mildly intoxicating amounts of ethanol. The combined effect increased according to the dose of THC and was strongest when the rats were seven days old.

The researchers also found that the CB1 receptor blocker drug Rimonabant reduced brain nerve cell death in rats given a combination of THC and ethanol. Rimonabant, brand named Acomplia, is an anti-obesity drug that may help treat addiction, the team noted. The fact that the drug counteracted the effect of THC and ethanol suggests that activation of CB1 receptors may be responsible for the effect that THC has on the neurotoxicity of ethanol, the researchers said.

The study was published in the journal Annals of Neurology.

More studies are needed to examine how THC boosts alcohol's harmful effects on the developing brain, the researchers said.

"With the use of behavioral and stereological techniques, such studies would explore whether acute changes reflect permanent neuronal loss and lead to behavioral deficits," they concluded. "The results of the acute studies have interesting potential therapeutic implications for including the use of CB1 receptor antagonists for preventing brain damage in fetuses and neonates exposed to ethanol, sedative and/or anticonvulsant drugs."