Pharmacological characterization of Adenosine A1 and A2 receptors in goat coronary artery.

Abstract

Adenosine, a purinergic neurotransmitter, has an essential role in vasodilation, particularly in vital organs like heart and brain. Any modulation in adenosine receptor function in these organs can have unfavourable outcome. Therefore, the present study was undertaken to investigate the pharmacological characteristics of adenosine A1 and A2 receptors and establish it as an experimental isolated tissue preparation. It was found that the isolated goat coronary strips were quiescent and did not show any spontaneous movements when mounted at 1 g basal tension in the modified KHS at 37°C. There was a predominance of A1 receptors over A2 receptors in goat coronary artery, as revealed by the rank order potency of adenosine analogues. The latter revealed that PEA (Phenyl ethyl adenosine) was the most potent while adenosine was the least effective in relaxing the goat coronary artery. From the contraction-relaxation studies, it is suggested that adenosine affects the release of Ca2+ from the intracellular stores in a more negative way than the influx of Ca2+ from extracellular source. Adenoceptor antagonist CGS~15943A was equipotent in inhibiting the relaxant reponses of A1 and A2 receptors.