Species-dependent effects of adenosine receptor agonists on contractile responses of vas deferens to ATP.
1. Experiments were carried out to examine the postjunctional actions of adenosine receptor agonists on the smooth muscle of the vas deferens of the guinea-pig and rabbit. 2. Although they produced neither contraction nor relaxation by themselves, adenosine analogues enhanced contractions of the guinea-pig vas deferens induced by 10 microm ATP. The rank order of potency was N6-cyclopentyladenosine (CPA) > 5'-N-ethylcarboxamidoadenosine (NECA) > adenosine > CGS 21680. Dose-response curves for NECA were shifted to the right by the nonselective adenosine receptor antagonist 8(p-sulphophenyl)theophylline (8-SPT; 100 microM) and by the selective A1-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 1 mM). 3. In the rabbit vas deferens, contractions induced by ATP (1 mM) were inhibited rather than facilitated by NECA. Neither CPA, R(-)-N6-(2-phenyl isopropyl)-adenosine (R-PIA) nor CGS 21680 had any effect. 4. The results indicate that the smooth muscle of the guinea-pig vas deferens expresses facilitatory adenosine A1 receptors but not adenosine A2 receptors. In contrast, in rabbit there are postjunctional inhibitory adenosine A2A receptors but not adenosine A1 receptors.
Smith
A D
AD
Department of Pharmacology, School of Medicine, University of Nevada, Reno 89557, USA.
Moloney
S
S
Khoyi
M A
MA
Westfall
D P
DP
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D006224:Cricetinae; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000187:drug effects*; D010627:Phenethylamines / Q000494:pharmacology; D058906:Purinergic P1 Receptor Agonists; D011817:Rabbits; D018047:Receptors, Purinergic P1 / Q000145:classification; D013045:Species Specificity; D014649:Vas Deferens / Q000187:drug effects*
D015226:Dinucleoside Phosphates; D010627:Phenethylamines; D058906:Purinergic P1 Receptor Agonists; D018047:Receptors, Purinergic P1; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C013907:cytidylyl adenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); D000241:Adenosine