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Peripheral Cannabinoid Receptor Agonist Inhibits Neuropathic Pain

http://www.medscape.com/viewarticle/459987

August 11, 2003
By Will Boggs, MD
Reuters Health
Newv York

AM1241, a selective activator of peripheral CB2 cannabinoid receptors, inhibits neuropathic pain in a rat model, according to a report in the August 11th PNAS Early Edition.

Medications currently used for treating neuropathic pain produce side effects related to their central nervous system activity, the authors explain, whereas targeting of peripheral CB2 cannabinoid receptor should avoid these problems.

"By targeting a specific class of cannabinoid receptors, we have developed selective cannabinoid drugs (drugs with actions similar to those of THC, the active ingredient in marijuana) that should lack the undesirable central nervous system side effects (such as sedation and anxiety) and the abuse potential of non-selective cannabinoid drugs," Dr. T. Philip Malan Jr. told Reuters Health.

Dr. Malan from University of Arizona in Tucson, Arizona and colleagues designed AM1241 and tested its effects on sensory hypersensitivity in a rat model of neuropathic pain.

AM1241 dose-dependently inhibited the tactile and thermal hypersensitivity in rats treated with spinal nerve ligation, the authors report.

The beneficial effects of AM1241 were completely blocked by a selective CB2 receptor antagonist but unaffected by a selective CB1 receptor antagonist, the report indicates.

"CB2 receptor agonists have been useful in a variety of pain models (acute pain, inflammatory pain, neuropathic pain)," Dr. Malan explained. "We have emphasized their actions in neuropathic pain because there is a strong need for new therapies for neuropathic pain."

CB2 receptors are found on immune cells, Dr. Malan pointed out, "and drugs acting on CB2 receptors can inhibit immune cell function. We do not believe that this will result in clinically deleterious immunosuppression (other drugs with similar effects do not), but this needs to be systematically tested."

Proc Natl Acad Sci USA 2003.
 

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