LA JOLLA, CA August 20, 2010 ERepeatedly boosting brain levels of one natural painkiller soon shuts down the brain cell receptors that respond to it, so that the painkilling effect is lost, according to a surprising new study led by Scripps Research Institute and Virginia Commonwealth University scientists. The study has important implications for drug development.
The natural painkiller, 2-AG, is one of the two major "endocannabinoid" neurotransmitters. The other, anandamide, can be kept at high levels in the brain without losing its therapeutic effects, and researchers had hoped that the same would be true for 2-AG.
"One implication is that maximally elevating 2-AG levels in the brain might not provide a straightforward path to new pain drugs," says Benjamin F. Cravatt III, PhD, professor and chair of the Department of Chemical Physiology and member of the Skaggs Institute for Chemical Biology at Scripps Research in La Jolla, California, who led the study with Aron Lichtman, PhD, a professor of pharmacology and toxicology at Virginia Commonwealth University in Richmond, Virginia. "But we remain optimistic that more modest elevations in 2-AG could produce sustained pain relief. Perhaps more importantly, on a basic science level, we've been able to tease apart a key difference between the two major endocannabinoid signaling pathways, since one can maximally elevate anandamide without observing tolerance."
The report appears in the August 22, 2010 issue of Nature Neuroscience.
A Better Chill Pill
Like the opioid system, the endocannabinoid system was discovered as a result of humans identifying a plant in this case marijuana (cannabis sativa) that artificially boosts its activity. Marijuana's main active ingredient, THC, typically reduces pain and anxiety. Researchers have sought to develop drugs that reproduce such therapeutic effects while leaving out THC's unwanted side effects which include memo
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Scripps Research Institute