title: Attenuation of morphine antinociceptive tolerance by cannabinoid CB1 and CB2 receptor antagonists.
abstract: Cannabinoid CB1 and CB2 receptor antagonists may be useful for their potential to increase or prolong opioid analgesia while attenuating the development of opioid tolerance. The aim of this study was to investigate the effects of AM251 (a selective CB1 antagonist) and JTE907 (a selective CB2 antagonist) on morphine analgesia and tolerance in rats. Adult male Wistar albino rats weighing 205-225 g were used in these experiments. To constitute morphine tolerance, we used a 3 day cumulative dosing regimen. After the last dose of morphine was injected on day 4, morphine tolerance was evaluated by analgesia tests. The analgesic effects of morphine (5 mg/kg), ACEA (a CB1 receptor agonist, 5 mg/kg), JWH-015 (a CB2 receptor agonist, 5 mg/kg), AM251 (1 mg/kg) and JTE907 (5 mg/kg) were considered at 30-min intervals (0, 30, 60, 90, and 120 min) by tail-flick and hot-plate analgesia tests. Our findings indicate that ACEA and JWH907 significantly increased morphine analgesia and morphine antinociceptive tolerance in the analgesia tests. In contrast, the data suggested that AM251 and JTE907 significantly attenuated the expression of morphine tolerance. In conclusion, we observed that co-injection of AM251 and JTE907 with morphine attenuated expression of tolerance to morphine analgesic effects and decreased the morphine analgesia.
authors.affiliation: Departments of Pharmacology, Cumhuriyet University School of Medicine, Sivas, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Altun
authors.forename: Kemal
authors.initials: K
authors.lastname: Yildirim
authors.forename: Ercan
authors.initials: E
authors.lastname: Ozdemir
authors.forename: Ihsan
authors.initials: I
authors.lastname: Bagcivan
authors.forename: Sinan
authors.initials: S
authors.lastname: Gursoy
authors.forename: Nedim
authors.initials: N
authors.lastname: Durmus
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D063386:Cannabinoid Receptor Agonists / Q000494:pharmacology; D063387:Cannabinoid Receptor Antagonists / Q000494:pharmacology*; D004149:Dioxoles / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D059225:Nociception / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D015363:Quinolones / Q000494:pharmacology*; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D063386:Cannabinoid Receptor Agonists; D063387:Cannabinoid Receptor Antagonists; C543264:Cnr1 protein, rat; C469526:Cnr2 protein, rat; D004149:Dioxoles; C422645:JTE 907; D010880:Piperidines; D011720:Pyrazoles; D015363:Quinolones; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; C103505:AM 251; D009020:Morphine