Most pot smokers will tell you their drug of choice is cooler than other recreational drugs. And if by "cooler," they mean "different", then they're right on. New research indicates that chemicals similar to those in marijuana, unlike those in other widely abused drugs, stimulate neuron growth in the brain.
Chronic use of opiates, alcohol, nicotine, or cocaine prevents stem cells from giving rise to new neurons in the hippocampus--a brain region important for learning and memory. Recent research suggests that neurogenesis in the hippocampus is impaired by depression--and boosted by drugs that treat depression and anxiety (ScienceNOW  7 August 2003). But researchers have found conflicting evidence with cannabinoids--the family of compounds that includes the active ingredient in marijuana. Some studies have shown that getting rid of the brain's cannabinoid receptors slows down new neuronal growth, suggesting that the body's own cannabinoids spur such growth. Other studies, however, suggest that the compounds actually prevent neuronal growth.
To get a grip on reality, neuroscientist Xia Zhang of the University of Saskatchewan, Saskatoon, Canada, and colleagues added a potent synthetic cannabinoid called HU210 to petri dishes containing neuronal stem cells. After two days, the treated cultures had almost 20% more cells than untreated ones. A different cannabinoid, present naturally in the brain, had the same effect. When the researchers injected HU210 twice daily into rats for 10 days, they found that the number of cells in a specific part of the hippocampus rose by almost 40%, compared to animals that didn't receive the drug. In addition, animals on HU210 exhibited fewer signs of depression and anxiety than did animals not taking the drug, the team reports 13 October in the Journal of Clinical Investigation.
This is the first time researchers have shown cannabinoids can stimulate neuronal growth, says neuroscientist Amelia Eisch of the University of Texas Southwestern Medical Center in Dallas. But that "does not mean we should all be out smoking pot," she says, noting that little is known about how closely HU210 mirrors better understood cannabinoids. Nonetheless, more research on the compound might reveal a better target for antidepressants, she says. And that would be totally cool, dude.