CP 55,940

CP 55,940 is a cannabinoid which mimics the effects of naturally occurring THC (one of the psychoactive compounds found in marijuana). CP 55,940 was created by Pfizer in 1974 but was never marketed. It is currently used to study the endocannabinoid system. Some effects that have been noted are a greatly decreased rates of lever pressing in exposed mice, and a greater reaction to opiates in exposed mice. There is also a recent study which shows that CP 55,940 can upregulate 5-HT2A receptors in mice.

CP 55,940 is 45 times more potent than Δ9-THC, and fully antagonized by rimonabant (SR141716A). CP 55,940 is considered a full agonist at both CB1 and CB2 receptors and has Ki values of 0.58nM and 0.68nM respectively, but is an antagonist at GPR55, the putative "CB3" receptor.

There is no information on the dangers or neurotoxicity of CP 55,940 except what can be inferred from its similarity to other cannabinoids, which typically exhibit neuroprotective properties.