Contribution of NO,ATP-sensitive K+ channels and prostaglandins to adenosine receptor agonists-induced relaxation of the rat tail artery

The mechanism of relaxation in the rat tail artery induced by the adenosine A1 receptor-selective agonist N⁶-cyclohexyladenosine (CHA, 10 nM–300 μM) and the adenosine A1/A_2a receptor agonist 5’-N-ethylcarboxamidoadenosine (NECA, 10 nM–300 μM) has been characterized. To do this, we used α₁-receptor agonist phenylephrine to evoke contraction (10 μM), and inhibitors of nitric oxide synthase (L-NAME, 10 μM), ATP-sensitive K⁺ channels (glibenclamide, 10 μM) and prostaglandin synthesis (indomethacin, 10 μM). CHA and NECA induced relaxation of rat-tail artery by 80% and 70% in a concentration-dependent manner, respectively. The relaxation effect of NECA was completely abolished in the presence of L-NAME, while glibenclamide and indomethacin prevented CHA-induced relaxation of the rat tail artery by approximately 25% and 40%, respectively. Our results indicate that nonspecific effects such nitric oxide and prostaglandins release or the activation of potassium channels significantly contributed to the effects of CHA and NECA.