Adenosine receptor subtypes mediating coronary vasodilation in rat hearts.

Adenosine receptor-mediated coronary vasodilation was studied in isolated hearts from young (1-2 months) and mature (12-18 months) Wistar rats. The nonselective agonist 5'-N-ethylcarboxamidoadenosine (NECA) induced biphasic concentration-dependant dilation with similar potencies in both age groups (p < 0.05).

Age-related changes in adenosine-mediated relaxation of coronary and aortic smooth muscle.

We tested whether adenosine mediates nitric oxide (NO)-dependent and NO-independent dilation in coronary and aortic smooth muscle and whether age selectively impairs NO-dependent adenosine relaxation. Responses to adenosine and the relatively nonselective analog 5'-N-ethylcarboxamidoadenosine (NECA) were studied in coronary vessels and aortas from immature (1-2 mo), mature (3-4 mo), and moderately aged (12-18 mo) Wistar and Sprague-Dawley rats. Adenosine and NECA induced biphasic concentration-dependent coronary vasodilation, with data supporting high-sensitivity (pEC(50) = 5.

Age-related changes in A(1)-adenosine receptor-mediated bradycardia.

The impact of age on functional sensitivity to A(1)-adenosine receptor activation was studied in Langendorff-perfused hearts from young (1-2 mo) and old (12-18 mo) male Wistar rats. Adenosine mediated bradycardia in young and old hearts, with sensitivity enhanced approximately 10-fold in old [negative logarithm of EC(50) (pEC(50)) = 4.56 +/- 0.