title: Adenosine analogues relax guinea-pig taenia caeci via an adenosine A2B receptor and a xanthine-resistant site.
abstract: In this study we have sub-classified the adenosine A2 receptor mediating relaxation in the guinea-pig taenia caecum using the adenosine A2A receptor-selective agonist CGS 21680 (2-[p-(2-carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine) and the adenosine A2A receptor-selective antagonist ZM 241385 (4-(2-[7-amino-2-(2-furyl) [1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-yl amino]ethyl)phenol). CGS 21680 did not elicit relaxations, and a pKB value of 7.80 was obtained for ZM 241385 against 5'-N-ethylcarboxamidoadenosine suggesting the presence of adenosine A2B receptors. Relaxations are also mediated via a xanthine-resistant site. In this study relaxations to the adenosine A3 receptor agonist IB-MECA (N6-(3-iodo-benzyl)adenosine-5'-N-methyluronamide) were blocked by neither 8-sulphophenyltheophylline (100 microM) nor the adenosine A3 receptor antagonist BW-A1433 (1,3-dipropyl-8-(4-acrylate)phenylxanthine, 100 microM), suggesting that this site is not an adenosine A3 receptor.
authors.affiliation: School of Biological Sciences, University of Surrey, Guildford, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Prentice
authors.forename: S M
authors.initials: SM
authors.lastname: Hourani
mesh_terms: D000241:Adenosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000818:Animals; D002432:Cecum / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D010627:Phenethylamines / Q000008:administration & dosage / Q000494:pharmacology*; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014227:Triazines / Q000494:pharmacology*; D014230:Triazoles / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D014227:Triazines; D014230:Triazoles; D014665:Vasodilator Agents; D014970:Xanthines; C097270:ZM 241385; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C056346:BW A1433; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline; D000241:Adenosine