Role for adenosine A1 and A2 receptors in femoral vasodilatation induced by intra-arterial adenosine in rabbits.
The vasodilator effects of adenosine injected into the femoral artery (i.a.) of rabbits were analyzed. Single bolus i.a. doses of adenosine (0.3-10 microg) and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA) (0.03-1 microg), an adenosine A2-receptor agonist, produced dose-dependent increases in femoral blood flow and decreases in resistance, almost without affecting blood pressure, heart rate, left ventricular (LV) pressure, and LVd P/dt max, even though CPCA elicited slight decreases in arterial blood pressure and LV pressure. On the other hand, bolus i.a. injections of N6-cyclopentyladenosine (CPA) (1-30 microg), an adenosine A1 receptor agonist, caused a relatively weak increase in blood flow, but markedly affected cardiac parameters, especially heart rate and LVd P/dt max. I.v. treatment with 3,7-dimethyl-1-propargylxanthine (DMPX)(2 mg kg(-1)), an antagonist of adenosine A2 receptors, or 8-phenyltheophylline (1 mg kg(-1)), an antagonist of adenosine A1 receptors, significantly attenuated the vasodilator response to adenosine, but not that to acetylcholine. Decreases in blood pressure, heart rate, LV pressure, LVdP/dt max and femoral vascular resistance, and increases in the blood flow elicited by CPA were not significantly modified by the DMPX treatment, but when this was combined with 8-phenyltheophylline, the responses to CPA were completely abolished. The present results indicate that the adenosine-induced femoral vasodilatation in rabbits may be mediated throughout activation of both adenosine A1 and A2 receptors.
Sakai
K
K
Central Research Laboratories, Chugai Pharmaceutical, Tokyo, Japan.
Yoshikawa
N
N
Akima
M
M
Saito
K
K
D000241:Adenosine / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure; D005263:Femoral Artery / Q000187:drug effects* / Q000502:physiology; D006339:Heart Rate; D007269:Injections, Intra-Arterial; D008297:Male; D011817:Rabbits; D018047:Receptors, Purinergic P1 / Q000145:classification / Q000502:physiology*; D012039:Regional Blood Flow; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D018047:Receptors, Purinergic P1; D000241:Adenosine