Endocannabinoids are naturally produced in the bodies of animals. After cannabinoid receptors were first discovered in the 1980s, scientists began searching for natural compounds that activate these receptors. In the early 1990s, the first such compound was identified as arachidonyl ethanolamine and named anandamide, a name derived from the Sanskrit word for bliss and amide. Anandamide is a polyunsaturated fatty acid with pharmacology similar to THC (THC is the primary psychoactive component of the cannabis plant), although its chemical structure is different.

Another endocannabinoid, 2-arachidonyl glycerol, is more abundant and less active than anandamide. When the body experiences pain under stressful circumstances, such as an injury during sport or even after a gunshot wound, the body is protected for a period of time - a response called stress-induced analgesia. A study in rats by the researchers from the University of California, Irvine, and the University of Georgia found, for the first time, how chemicals play a part in this process. Production of one cannabinoid compound, 2-AG, was found to be triggered by stress-related pain.

This is the first time anyone has shown that one of the body's natural occurring cannabinoids, 2-AG, has anything to do with pain regulation under natural conditions.

Formal Chemical Name (IUPAC)
(5Z,8Z,11Z,14Z)-1,3-dihydroxypropan-2-yl icosa-5,8,11,14-tetraenoate

References

http://en.wikipedia.org/wiki/Cannabinoids

http://news.bbc.co.uk/1/hi/health/4119346.stm