title: The potent emetogenic effects of the endocannabinoid, 2-AG (2-arachidonoylglycerol) are blocked by delta(9)-tetrahydrocannabinol and other cannnabinoids.
abstract: Cannabinoids, including the endogenous cannabinoid or endocannabinoid, anandamide, modulate several gastrointestinal functions. To date, the gastrointestinal effects of the second putative endocannabinoid 2-arachidonoylglycerol (2-AG) have not been studied. In the present study using a shrew (Cryptotis parva) emetic model, 2-AG (0.25-10 mg/kg, i.p.) potently and dose-dependently increased vomiting frequency (ED(50) = 1.13 mg/kg) and the number of animals vomiting (ED(50) = 0.48 mg/kg). In contrast, neither anandamide (2.5-20 mg/kg) nor methanandamide (5-10 mg/kg) induced a dose-dependent emetogenic response, but both could partially block the induced emetic effects. Delta(9)-Tetrahydrocannabinol and its synthetic analogs reduced 2-AG-induced vomiting with the rank order potency: CP 55,940 > WIN 55,212-2 > Delta(9)-tetrahydrocannabinol. The nonpsychoactive cannabinoid, cannabidiol, was inactive. Nonemetic doses of SR 141716A (1-5 mg/kg) also blocked 2-AG-induced vomiting. The 2-AG metabolite arachidonic acid also caused vomiting. Indomethacin, a cyclooxygenase inhibitor, blocked the emetogenic effects of both arachidonic acid and 2-AG. CP 55,940 also blocked the emetic effects of arachidonic acid. 2-AG (0.25-10 mg/kg) reduced spontaneous locomotor activity (ED(50) = 11 mg/kg) and rearing frequency (ED(50) = 4.3 mg/kg) in the shrew, whereas such doses of both anandamide and methanandamide had no effect on locomotor parameters. The present study indicates that: 1) 2-AG is an efficacious endogenous emetogenic cannabinoid involved in vomiting circuits, 2) the emetic action of 2-AG and the antiemetic effects of tested cannabinoids are mediated via CB(1) receptors, and 3) the emetic effects of 2-AG occur in lower doses relative to its locomotor suppressant actions.
authors.affiliation: Department of Pharmacology, Kirksville College of Osteopathic Medicine, Kirksville, Missouri 63501, USA. ndarmani@kcom.edu
authors.forename: Nissar A
authors.initials: NA
authors.lastname: Darmani
mesh_terms: D000818:Animals; D000932:Antiemetics / Q000494:pharmacology*; D001095:Arachidonic Acids / Q000494:pharmacology; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids / Q000494:pharmacology*; D003511:Cyclohexanols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology*; D004639:Emetics / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D063388:Endocannabinoids; D005260:Female; D005989:Glycerides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D000077285:Rimonabant; D012788:Shrews
chemical_list: D000932:Antiemetics; D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D003511:Cyclohexanols; D004639:Emetics; D063388:Endocannabinoids; D005989:Glycerides; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C088155:methanandamide; D013759:Dronabinol; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; C094503:glyceryl 2-arachidonate; D000077285:Rimonabant; C078814:anandamide