DISCRIMINATIVE STIMULUS EFFECTS OF ANANDAMIDE IN RATS

Anandamide (arachidonylethanolamide), a putative endogenous ligand for the cannabinoid receptor, produces a tetrad of behavioral effects in mice characteristic of psychoactive cannabinoids including catalepsy, antinociception, hypothermia, and hypomobility. The present study exam ined the discriminative stimulus effects of anandamide in rats trained to discriminate dg-tetrahydrocannabinol or the potent cannabinoid rec eptor ligand CP 55,940 yl)phenyl]-trans-4-(3-hydraxypropyl)cyclohexano l)] from vehicle. Intraperitoneal injections of anandamide substituted for dg-tetrahydrocannabinol and for CP 55,940; however, unlike substi tution dose-effect curves with the training drugs, anandamide substitu tion occurred at a single dose (30 or 45 mg/kg) and was accompanied by severe decreases in response rates. The results of the present study suggest that, although systemic anandamide administration may have can nabimimetic effects similar to those of Delta(9)-tetrahydrocannabinol and CP 55,940, some differences in the behavioral effects of anandamid e and other psychoactive cannabinoids also are apparent.