title: Differential effects of presynaptic versus postsynaptic adenosine A2A receptor blockade on Δ9-tetrahydrocannabinol (THC) self-administration in squirrel monkeys.
abstract: Different doses of an adenosine A2A receptor antagonist MSX-3 [3,7-dihydro-8-[(1E)-2-(3-ethoxyphenyl)ethenyl]-7 methyl-3-[3-(phosphooxy)propyl-1-(2 propynil)-1H-purine-2,6-dione] were found previously to either decrease or increase self-administration of cannabinoids delta-9-tetrahydrocannabinol (THC) or anandamide in squirrel monkeys. It was hypothesized that the decrease observed with a relatively low dose of MSX-3 was related to blockade of striatal presynaptic A2A receptors that modulate glutamatergic neurotransmission, whereas the increase observed with a higher dose was related to blockade of postsynaptic A2A receptors localized in striatopallidal neurons. This hypothesis was confirmed in the present study by testing the effects of the preferential presynaptic and postsynaptic A2A receptor antagonists SCH-442416 [2-(2-furanyl)-7-[3-(4-methoxyphenyl)propyl]-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine] and KW-6002 [(E)-1, 3-diethyl-8-(3,4-dimethoxystyryl)-7-methyl-3,7-dihydro-1H-purine-2,6-dione], respectively, in squirrel monkeys trained to intravenously self-administer THC. SCH-442416 produced a significant shift to the right of the THC self-administration dose-response curves, consistent with antagonism of the reinforcing effects of THC. Conversely, KW-6002 produced a significant shift to the left, consistent with potentiation of the reinforcing effects of THC. These results show that selectively blocking presynaptic A2A receptors could provide a new pharmacological approach to the treatment of marijuana dependence and underscore corticostriatal glutamatergic neurotransmission as a possible main mechanism involved in the rewarding effects of THC.
authors.affiliation: Preclinical Pharmacology Section of Behavioral Neuroscience Research Branch and Integrative Neurobiology Section of Molecular Targets and Medications Discovery Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland 21224.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Justinová
authors.forename: Godfrey H
authors.initials: GH
authors.lastname: Redhi
authors.forename: Steven R
authors.initials: SR
authors.lastname: Goldberg
authors.forename: Sergi
authors.initials: S
authors.lastname: Ferré
mesh_terms: D058917:Adenosine A2 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008297:Male; D002189:Marijuana Abuse / Q000188:drug therapy; D011687:Purines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D043705:Receptor, Adenosine A2A / Q000187:drug effects*; D017661:Receptors, Presynaptic / Q000187:drug effects*; D012054:Reinforcement, Psychology; D012201:Reward; D012453:Saimiri; D012646:Self Administration; D013569:Synapses / Q000187:drug effects*; D014970:Xanthines / Q000494:pharmacology
chemical_list: D058917:Adenosine A2 Receptor Antagonists; C113602:MSX 3 compound; D011687:Purines; D011720:Pyrazoles; D011743:Pyrimidines; D043705:Receptor, Adenosine A2A; D017661:Receptors, Presynaptic; D014970:Xanthines; C111599:istradefylline; D013759:Dronabinol; C416650:SCH 442416
keywords: THC; adenosine A2A receptor; cannabinoids; drug abuse; monkey; self-administration