University of Calgary scientists have discovered a new brain receptor that is manipulated by chemicals similar to cannabis and could hold the key to reducing nausea in cancer and AIDS patients.
An international team of researchers, led by Calgary's Dr. Keith Sharkey, has stumbled across the previously unknown CB2 cannabinoid receptor, located in the brain stem. The team's findings are being published today in the journal Science.
"Our discovery could lead to new, therapeutic advances for vomiting," said Sharkey.
Other experts in the field say the receptor could be involved in diseases of the central nervous system, such as multiple sclerosis and Parkinson's.
Scientists have long known about a cannabinoid receptor, known as CB1, which is located on immune cells.
Sharkey's team, including researchers from Canada, Italy and the United States, was researching the effect of chemical agents on CB1 when they made an accidental discovery.
After injecting laboratory animals with chemical agents, they found some surprising effects they could only attribute to the presence of a second, undetected receptor they named CB2.
To prove the existence of the new receptor, the scientists injected the agents in a variety of animals, including rats, mice and ferrets.
"It's widespread in every species," he said.
Located at the back of the brain, the CB2 receptor is present on nerves that control vomiting.
The body has natural chemical messengers -- similar to plant-derived cannabis -- that can inhibit the vomiting nerves by acting on the receptor.
Although marijuana mimics the body's chemical messengers, Sharkey says ingesting or smoking the drug doesn't have the same effect on the CB2 receptor.
Instead, Sharkey said researchers will have to develop drugs to manipulate the body's own chemical messengers to act as "keys" that will unlock the CB2 receptor and bring nausea under control.
New therapies could control nausea experienced by cancer and AIDS patients as well as pregnant women, he said.
Several therapies have already been developed to target the CB1 receptor, which also controls nausea, but they cause patients to feel stoned. Sharkey hopes the discovery of CB2 will lead to drugs without that side-effect.