Abstract
Based on binding, functional, and pharmacological data, this study introduces SR147778 [5-(4-bromophenyl)-1-(2,4-dichloro-phenyl)-4-ethyl-N-(1-piperidinyl)-1H-pyrazole-3-carboxamide] as a highly potent, selective, and orally active antagonist for the CB1 receptor. This compound displays nanomolar affinity (Ki = 0.56 and 3.5 nM) for both the rat brain and human CB1 recombinant receptors, respectively. It has low affinity (Ki = 400 nM) for both the rat spleen and human CB2 receptors. Furthermore, it shows no affinity for any of the over 100 targets investigated (IC50 > 1 μM). In vitro, SR147778 antagonizes the inhibitory effects of CP 55,940 [(1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl)cyclohexan-1-ol] on both the mouse vas deferens contractions (pA2 value = 8.1) and on forskolin-stimulated adenylyl cyclase activity in the U373 MG cell lines (pA2 value = 8.2) but not in Chinese hamster ovary (CHO) cells permanently expressing the human peripheral cannabinoid receptor (hCB2). SR147778 is able to block the mitogen-activated protein kinase activity induced by CP 55,940 in the CHO cell line expressing human brain cannabinoid receptor (IC50 = 9.6 nM) but was inactive in cells expressing hCB2. After oral administration, SR147778 displaced the ex vivo [3H]-CP 55,940 binding to mouse brain membranes (ED50 = 3.8 mg/kg) with a long duration of action, whereas it did not interact with the CB2 receptor expressed in the mouse spleen. Using different routes of administration, SR147778 (0.3–3 mg/kg) is shown to antagonize pharmacological effects (hypothermia, analgesia, and gastrointestinal transit) induced by R-(+)-(2,3-dihydro-5-methyl-3-[{4-morpholinyl}methyl] pyrol [1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone in mice. Finally, per se, SR147778 (0.3–10 mg/kg) is able to reduce ethanol or sucrose consumption in mice and rats and food intake in fasted and nondeprived rats.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.104.067884.
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ABBREVIATIONS: Δ9-THC, tetrahydrocannabinol; SR147778, 5-(4-bromophenyl)-1-(2,4-dichlorophenyl)-4-ethyl-N-(1-piperidinyl)-1H-pyrazole-3-carboxamide; CP 55,940, (1R,3R,4R)-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-4-(3-hydroxypropyl)cyclohexan-1-ol; SIP, schedule-induced ethanol polydipsia; CHO, Chinese hamster ovary; hCB1, human brain cannabinoid receptor; hCB2, human peripheral cannabinoid receptor; PBS, phosphate-buffered saline; PTX, pertussis toxin; MAPK, mitogen-activated protein kinase; ANOVA, analysis of variance; CL, confidence limit; RO20-1724, 4-[(3-butoxy-4-methoxyphenyl)methyl]2-imidazolidinone; JWH133, (6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran; WIN55212-2, R-(+)-(2,3-dihydro-5-methyl-3-[{4-morpholinyl}methyl] pyrol [1,2,3-de]-1,4-benzoxazin-6-yl)(1-naphthalenyl) methanone; SR141716, N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methylpyrazole-3-carboxamide, AEA, arachidonyl ethanolamide.
- Received March 3, 2004.
- Accepted May 3, 2004.
- The American Society for Pharmacology and Experimental Therapeutics
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