Dec. 2, 2002 -- A distant chemical relative of marijuana may hold the promise of relieving depression and anxiety without the negative side effects of a marijuana high.
A new study shows the synthetic forms of the active ingredient in marijuana are gentler on the brains of animals and work much in the same way as popular antidepressants such as Prozac, Zoloft, Celexa, and Paxil.
Initial results from laboratory tests of the experimental new drugs appear on Nature Medicine's web site and will be published in the January 2003 issue of the journal.
Researchers say it's the first study to demonstrate how anxiety is controlled by a natural network of chemicals in the brain known as anandamides, which play a role in regulating pain, mood, and other psychological functions, and may pave the way for new treatments for mental disorders.
The active ingredient in marijuana, THC, is already known to affect this system of nerve transmitters, but at a price.
"THC reduces anxiety by binding directly to receptors in the brain and resulting in its familiar 'high' sensation," says study researcher Daniele Piomelli, PhD, of the department of pharmacology at the University of California, Irvine, in a news release. "The reaction is too strong, creating marijuana's side effects."
Side effects of THC include dizziness, lethargy, and in some cases miscarriage or stillbirth among women.
In this study, researchers identified two synthetic forms of THC, called URB532 and URB595, which worked in a gentler way than marijuana to relieve anxiety and depression.
Rather than acting directly on the receptors in the brain, the drugs inhibited the activity of an enzyme that breaks apart anandamide -- keeping levels of natural anti-depressant for many hours after a single dose without significant side effects.
Researchers say the effect is similar as that achieved by antidepressants known as SSRIs (selective serotonin reuptake inhibitors) that act on serotonin, another natural antidepressant chemical in the brain.
Although the results are promising, the study authors stress that much more research is needed before these drugs can be tested on humans.