To determine the involvement of purinergic receptors in coronary endothelium-dependent relaxation, the response to acetylcholine (1 × 10<sup>-8</sup> to 3 × 10<sup>-7</sup><smlcap>M</smlcap>) was recorded in isolated rat hearts perfused according to the Langendorff procedure before and after 30 min of ischemia and 15 min of reperfusion and after the inhibition of nitric oxide synthesis with <smlcap>L</smlcap>-NAME (10<sup>-4</sup><smlcap>M</smlcap>), in the absence and presence of the antagonist of purinergic P2X receptors, PPADS (3 × 10<sup>-6</sup><smlcap>M</smlcap>), and of the antagonist of purinergic P2Y receptors, Reactive Blue 2 (3 × 10<sup>-7</sup><smlcap>M</smlcap>). In control conditions, the relaxation to acetylcholine was not altered by PPADS or Reactive Blue 2. The relaxation to acetylcholine was reduced after ischemia-reperfusion, and, in this condition, it was further reduced by treatment with PPADS or Reactive Blue 2. Likewise, the relaxation to acetylcholine was reduced by <smlcap>L</smlcap>-NAME, and reduced further by Reactive Blue 2 but not by PPADS. These results suggest that the relaxation to acetylcholine may be partly mediated by purinergic receptors after ischemia-reperfusion, due to the reduction of nitric oxide release in this condition.