Cannabis joins battle of the bulgeThe drug that gives smokers the munchies
could also suppress hunger
Alok Jha, science correspondent
Scientists have unveiled an unlikely weapon in the battle against the bulge: cannabis. More specifically, one of its key ingredients, which has been found to suppress appetite.
Anyone who has ever inhaled will know the feeling: an inescapable desire to eat everything in sight, a state called the munchies. It stems from the action of tetrahydrocannabinol (THC), one of the active ingredients in cannabis, on specific appetite-control receptors in the brain. The chemical also causes the body to lay down more fat.
But Roger Pertwee, a neuropharmacologist at Aberdeen University, said yesterday at the British Association festival of science that there is more to the cannabis story.
"We've discovered to our surprise that cannabis, as well as containing a drug that boosts appetite, contains a drug which has a blocking effect," said Professor Pertwee. "The work so far has been working with tissue and we've yet to see what this drug does when we give it to a whole organism and what it does when we give it to humans."
The drug, known as tetrahydrocannabivarin (THCV), works on the same receptors as THC but has entirely the opposite effect. The research will be published in the British Journal of Pharmacology.
THCV is not the first appetite suppressant to be inspired by cannabis. The drug Rimonabant works by blocking the brain receptors that the body's own cannabinoid compounds - released when we comfort eat - attach themselves to. Because the cannabinoids do not reach the receptors in a person taking Rimonabant, they will feel less compulsion to eat.
Why THCV does not manifest itself to people who smoke cannabis is a mystery, but Prof Pertwee said it might have something to do with the proportions of the various ingredients in the drug. "The relative proportions of THC and THCV vary from cannabis to cannabis," he said.
"There is a large amount of THCV in Pakistani cannabis, which is the one used to make a medicine called 'tincture of cannabis'. That contained about equal amounts of THC and THCV."
Prof Pertwee said that there were several promising medicinal compounds to be derived from cannabis, both for boosting the effects of the body's own cannabinoids and for blocking them.
Boosting the cannabinoids could bring pain relief, for example, and relieve spasms for sufferers of multiple sclerosis. Prof Pertwee added that there was also evidence that the compounds had a protective effect against cancer.
As well as controlling appetite, developing drugs that block the body's cannabinoids could help people to quit smoking by stopping nicotine having any effect on the brain.