Scientists devise a new approach to an old problem -- relieving pain

Among other things, marijuana is known to relieve pain. Scientists believe the cannibinoids deserve the credit, though they’re not exactly sure how they work their magic. Unfortunately, the cannibinoids also get into the brain, where they can cause a variety of problems.

So researchers at UC Irvine and their colleagues set out to design a molecule that relieves pain like cannibinoids, but doesn’t cause any mischief in the brain.

They started with a compound called URB597, which is a known analgesic. Then they added chemical groups to it, making it bigger. One of the combinations – which they dubbed URB937 – acted the same way but didn’t stick in the central nervous system or brain.

Further tests revealed that the new compound probably does cross the blood-brain barrier, but gets “extruded” from the central nervous system. However, it did travel rapidly throughout the body, hitching a ride in the bloodstream.

When given to mice, URB937 boosted levels of a cannibinoid neurotransmitter (called anandamide) in body tissues, but not the brain. In a variety of tests, the researchers determined that the compound reduced pain in mice and rats suffering from pain caused by nerve damage, inflammation and damage to internal organs.

The researchers believe that the compound works by blocking an enzyme that would otherwise break down anandamide and prevent it from activating a “bliss receptor.” They said this mechanism of action is totally unlike that of traditional painkillers. But they cautioned that it could take years to turn this molecule into a marketable drug.

The study was published online Sunday by the journal Nature Neuroscience.

-- Karen Kaplan/Los Angeles Times