Anandamide (AEA) was the first endogenous cannabinoid to be isolated and characterized as an agonist acting on the same receptors (CB1 and CB2) as tetrahydrocannabinol (THC). Arachidonoyl 2-chloroethylamide (ACEA) is a potent, stable, and selective agonist analog of AEA. ACEA has a Ki value of 1.4 nM at the isolated rat CB1 receptor, and is 1,400 times more potent at the CB1 compared with the CB2 receptor. In whole animal experiments, ACEA induces hypothermia in mice with the same efficacy as AEA, in spite of its much higher affinity for the CB1 receptor. These data have been interpreted to indicate that ACEA may be a substrate for fatty acid amide hydrolase (FAAH), and thus only transiently available in whole animal experiments.
