A chemical in marijuana might protect against brain damage from a stroke, according to a report in tomorrow's Proceedings of the National Academy of Sciences. The compound, called cannabidiol, in the test tube sops up damaging oxygen-free radicals more effectively than vitamins C and E, two of the most powerful known dietary antioxidants.
As every pothead knows, marijuana and its psychoactive component tetrahydrocannabinol (THC) inhibit the activity of certain brain regions. Aidan Hampson, working jointly with colleagues at the National Institute of Mental Health and elsewhere, set out to test whether THC's inhibitory effects might also prevent the toxic overstimulation of brain cells that results when the brain cells become starved for oxygen and sugar, and are then unable to pump out the neurotransmitter glutamate.
The researchers simulated a stroke by bathing a petri dish full of neurons in the neurotransmitter glutamate, which is toxic at high doses. When they added purified THC, half as many neurons died. At first the researchers assumed that THC was binding to the cannabinoid receptor, but when they added another chemical that blocks the receptor, THC still protected the cells. "It shouldn't have protected the neurons, but it worked just as well," Hampson says. Further testing showed that THC was mopping up free radicals, such as hydrogen peroxide, that are spewed out by overstimulated neurons. They also showed that cannabidiol, a marijuana component similar to THC but lacking its psychoactive effects, provided the same antioxidant benefits.
Hampson is already at work simulating strokes in rats and trying to prevent the damage with cannabidiol. But pharmacologist Steve Childers, of Wake Forest University Medical School in Winston-Salem, North Carolina, is skeptical that cannabidiol would be effective at preventing strokes in people at safe doses. "They're not testing a very low concentration of the compound," he points out.