title: Chronic Δ⁹-tetrahydrocannabinol treatment in rhesus monkeys: differential tolerance and cross-tolerance among cannabinoids.
abstract: OBJECTIVE
  The extent to which behavioural effects vary as a function of CB₁ receptor agonist efficacy is not clear. These studies tested the hypothesis that cannabinoid tolerance and cross-tolerance depend upon the CB₁ agonist efficacy of drugs to which tolerance/cross-tolerance develops.
  
  
  METHODS
  Sensitivity to cannabinoids, including the cannabinoid antagonist rimonabant, low efficacy agonist Δ⁹-tetrahydrocannabinol (Δ⁹-THC), and high efficacy agonists CP 55940 and WIN 55212-2, was determined before and after chronic Δ⁹-THC treatment in rhesus monkeys. Two measures of behavioural effect were assessed: effects of drugs to decrease fixed ratio responding for food presentation and stimulus-shock termination and discriminative stimulus effects in monkeys discriminating Δ⁹-THC (0.1 mg·kg⁻¹, i.v.).
  
  
  RESULTS
  Δ⁹-THC decreased responding for both food presentation and stimulus-shock termination; these effects were antagonized by the CB₁ antagonist rimonabant. Chronic Δ⁹-THC (1 mg·kg⁻¹ per 12 h, s.c.) resulted in tolerance to the rate-decreasing effects of Δ⁹-THC and cross-tolerance to CP 55940 and WIN 55212-2; however, cross-tolerance was less than tolerance. Chronic Δ⁹-THC increased sensitivity to rimonabant without changing sensitivity to the non-cannabinoids midazolam and ketamine. In monkeys discriminating Δ⁹-THC (0.1 mg·kg⁻¹, i.v.), both CP 55940 and WIN 55212-2 produced high levels of drug-lever responding. Chronic Δ⁹-THC (1 mg·kg⁻¹ per day, s.c.) decreased sensitivity to Δ⁹-THC without producing cross-tolerance to CP 55940 or WIN 55212-2.
  
  
  CONCLUSIONS
  In Δ⁹-THC-treated monkeys, the magnitude of tolerance and cross-tolerance to other CB₁ receptor agonists varied inversely with agonist efficacy, suggesting that CB₁ agonist efficacy is an important determinant of behavioural effects.
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, USA. mcmahonl@uthscsa.edu
authors.forename: Lance R
authors.initials: LR
authors.lastname: McMahon
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D048588:Benzoxazines / Q000494:pharmacology; D002186:Cannabinoids / Q000008:administration & dosage / Q000819:agonists / Q000037:antagonists & inhibitors; D003511:Cyclohexanols / Q000494:pharmacology; D004193:Discrimination Learning / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000008:administration & dosage*; D004361:Drug Tolerance / Q000502:physiology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000037:antagonists & inhibitors; D000077285:Rimonabant
chemical_list: D048588:Benzoxazines; D002186:Cannabinoids; D003511:Cyclohexanols; D009025:Morpholines; D009281:Naphthalenes; D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D013759:Dronabinol; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D000077285:Rimonabant