The body makes compounds that work like marijuana to suppress pain, a new study in the journal Nature shows.
"This study shows for the first time that natural marijuana-like chemicals in the brain have a link to pain suppression," says researcher Daniele Piomelli, PhD, in a news release.
Those chemicals are called cannabinoids. They act like those in marijuana, says Piomelli. He is a pharmacology professor and director to the Center for Drug Discovery at the University of California at Irvine's medical school.
The study was based on rats, not people. However, the findings may lead to new pain treatments, says Piomelli. "If we design chemicals that can tweak the levels of these cannabinoid compounds in the brain, we might be able to boost their normal effects," he says.
Putting Pain on Hold
Pain doesn't always register right away. It can briefly be buffered, say Piomelli and colleagues.
That phenomenon, called stress-induced analgesia, was the focus of their experiment. In stress-induced analgesia, a sudden injury activates certain brain pathways, temporarily suppressing pain, say the researchers.
Their tests showed a rapid rise in the levels of a cannabinoid called 2-AG in male rats' brains after injury.
But 2-AG doesn't hold off pain forever. Ordinarily, it subsides after a short time, ushered away by an enzyme also made by the body.
The study targeted that enzyme, called monoacylglycerol lipase (MGL). With MGL sidelined, 2-AG stayed in the brain for longer than normal. Under those circumstances, stress-induced analgesia increased. In other words, pain stayed at bay longer.
MGL may be a previously unrecognized therapeutic target, write researchers.
"There is no prescription or over-the-counter drug that allows us to manipulate the level of the brain's marijuana-like compounds," says researcher Andrea Hohmann, PhD, in a news release.
A drug based on the new research would likely be more effective and specific than smoked marijuana, says Hohmann. She is a neuroscientist in the University of Georgia's psychology department who also worked on the experiment.
The chemical used to inhibit MGL in the study was developed by Piomelli's group. It has been patented by the University of California at Irvine and the Italian universities of Urbino and Parma, according to the news release.
SOURCES: Hohmann, A. Nature, June 23, 2005; vol 435: pp 1108-1112. News release, University of California at Irvine. News release, University of Georgia.