Neuroscience: No brain pain control

Pain is inhibited by the binding of cannabinoid compounds with their receptor molecules. Now scientists have identified the endogenous cannabinoid responsible — anandamide. Unexpectedly, they have also shown that its full analgesic effect can be achieved when the cannabinoid receptor CB₁ is activated solely in tissues outside the brain.

Daniele Piomelli at the Italian Institute of Technology in Genoa and his colleagues developed a small molecule, URB937, that blocks the breakdown of anandamide but cannot access the brain. Rats injected with URB937 displayed reduced responses to several different types of pain.

The discovery may offer a new approach to pain therapy that avoids the risk of a 'cannabis high', the authors say.

Nature Neurosci. doi:10.1038/nn.2632 (2010)