Relaxation of mouse isolated aorta to adenosine and its analogues does notinvolve adenosine A(1), A(2) or A(3) receptors

Relaxations to adenosine and analogues were investigated in the mouse aorta in the presence of the adenosine A, receptor-selective antagonist 1,3-dipr opyl-8-cyclopentylxanthine (DPCPX, 30 nM), which did not affect relaxations to adenosine or its analogue N-6-R-phenylisopropyladenosine (R-PIA) but ab olished contractile adenosine Al receptor-mediated responses to these agoni sts. Relaxations to adenosine, 5'-N-ethylcarboxamidoadenosine, R-PIA, 2-[ p -(2-carbonylethyl)-phenylethylamino]-5'-N-ethy;carboxamidoadensine (CGS 216 80), and N-6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) were u naffected by the adenosine A(1)/A(2) receptor antagonist 8-sulphophenyltheo phylline (100 muM). IB-MECA. relaxations were unaffected by the adenosine A , receptor-selective antagonist 3-ethyl-5-benzyl-2-methyl-6-phenyl-4-phenyl ethnyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191, 30 muM) and R- PIA relaxations were unaffected by NG-nitro-L-arginine methyl ester (100 m uM) and endothelium removal. In conclusion, relaxant responses to adenosine and analogues do not involve adenosine A,, A, or A, receptors and are endo thelium- and nitric oxide-independent. (C) 2001 Elsevier Science B.V. All r ights reserved.