A compound known as methyllycaconitine (MLA) appears to block craving for and the effects of a synthetic version of THC, the main active ingredient in marijuana, New Scientist reported May 22.

Animal tests revealed that MLA, derived from Delphinium brownii, a plant in the buttercup family, cut craving for THC and blocked the brain's reward response for the drug. Rats that received injections of MTA pushed a lever for doses of THC 70 percent fewer times than on days where they did not receive MLA.

Studies of the rats' brains also showed that THC did not increase dopamine levels when MLA was present. "The increases in dopamine are virtually nonexistent because of MLA," said lead researcher Steven Goldberg of the National Institute on Drug Abuse, who said the findings could have implications for addiction treatment for humans.

The study was published in the Journal of Neuroscience.