Evaluation of the cannabinoid CB2 receptor-selective antagonist, SR144528: further evidence for cannabinoid CB2 receptor absence in the rat central nervous system.
The aim of this study was to characterize the activity of the cannabinoid CB2 receptor selective antagonist, N-[(1S)-endo-1,3,3-trimethyl bicyclo[2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazo le-3-carboxamide] (SR144528) in a number of biochemical assays and to look for evidence of cannabinoid CB2 receptors in the rat central nervous system. SR144528 displaced [3H]CP 55,940 ((-)-3-[2-hydroxyl-4-(1,1-dimethylheptyl)-phenyl]-4-[3-hydroxyprop yl]cyclohexan-1-ol) from binding sites in CB2- and CB1-transfected cells (Ki = 0.67+/-0.30 and 33.0+/-5.09 nM) and from rat cerebellum and whole brain membrane homogenates (Ki = 54.7+/-9.70 and 54.8+/-7.86 nM). In the GTPgammaS binding assay, SR144528 antagonized a number of cannabinoid receptor agonists (K(B) values ranging from 26.3 to 76.6 nM) in rat cerebellar membranes and in rat whole brain membranes (K(B) = 50.8 nM). SR144528 also antagonized CP 55,940-stimulated GTPgammaS binding in a CB2-expressing cell line (K(B) = 6.34 nM). In Xenopus oocytes co-expressing the CB1 receptor and G-protein coupled inwardly rectifying K+ channels (GIRK 1/4), SR144528 antagonized WIN 55212-2((R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrolo [1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthalenyl)methanone) -stimulated K+ currents (K(B) = 558 nM). In summary, this report characterizes the cannabinoid CB2 receptor-selective cannabinoid antagonist, SR144528, and additionally suggests an absence of cannabinoid CB2 receptors in the rat central nervous system, an observation confirmed by Northern blot.
Griffin
G
G
Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
Wray
E J
EJ
Tao
Q
Q
McAllister
S D
SD
Rorrer
W K
WK
Aung
M M
MM
Martin
B R
BR
Abood
M E
ME
D000818:Animals; D048588:Benzoxazines; D001667:Binding, Competitive; D015152:Blotting, Northern; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D001892:Camphanes / Q000378:metabolism / Q000494:pharmacology*; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D011720:Pyrazoles / Q000378:metabolism / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors* / Q000235:genetics; D014018:Tissue Distribution; D014982:Xenopus laevis
D048588:Benzoxazines; D002121:Calcium Channel Blockers; D001892:Camphanes; C469526:Cnr2 protein, rat; D009025:Morpholines; D009281:Naphthalenes; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011720:Pyrazoles; D012333:RNA, Messenger; D043885:Receptor, Cannabinoid, CB2; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C110630:SR 144528; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D019204:GTP-Binding Proteins