SR 141716A differentially attenuates the behavioral effects of delta9-THC in rhesus monkeys.
The prototypic cannabinoid CB1 antagonist SR 141716A is one important pharmacologic tool for examining CB1 receptors that mediate the behavioral and physiologic effects of delta9-tetrahydrocannabinol (delta9-THC). This study examined the effects of SR 141716A on the rate-decreasing, hypothermic and discriminative stimulus effects of delta9-THC in rhesus monkeys. In monkeys (n=4) responding under a multiple fixed ratio (FR-10:FR-10) schedule of food presentation and stimulus-shock termination, the potency of i.m. delta9-THC to decrease responding in the food component (ED50=0.64 mg/kg) was threefold greater than its potency in the stimulus-shock termination component (ED50=2.14 mg/kg). In the same monkeys, hypothermia was induced by delta9-THC at a dose (e.g. 0.32 mg/kg) that did not alter responding in either schedule component; the maximum decrease was 2.1 degrees C at a dose of 3.2 mg/kg. A dose of 0.32 mg/kg of SR 141716A, significantly attenuated delta9-THC-induced hypothermia without attenuating the rate-decreasing effects of delta9-THC in either component of the multiple schedule. The largest dose of i.m. SR 141716A that was studied, 1.0 mg/kg, significantly decreased rectal temperature and responding in the food component but did not significantly decrease responding in the stimulus-shock termination component of the multiple schedule. In a separate group of monkeys (n=3) that discriminated i.v. delta9-THC (0.1 mg/kg) while responding under an FR-5 schedule of stimulus-shock termination, SR 141716A (0.32 and 1 mg/kg) significantly increased the ED50 of the delta9-THC by 2.3- and 3.7-fold, respectively. Collectively, these results demonstrate that the behavioral effects of delta9-THC are not equally attenuated by SR 141716A.
McMahon
L R
LR
Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA. mcmahonl@uthscsa.edu
Amin
M R
MR
France
C P
CP
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects* / Q000502:physiology; D001831:Body Temperature / Q000187:drug effects; D004192:Discrimination, Psychological / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D010880:Piperidines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology; D000077285:Rimonabant; D013997:Time Factors
D010880:Piperidines; D011720:Pyrazoles; D043884:Receptor, Cannabinoid, CB1; D013759:Dronabinol; D000077285:Rimonabant