Pretreatment with indomethacin modulates the effects of selective adenosine receptor agonists on the contractility and effective refractory period in the guinea pig heart.

The effects of selective adenosine receptor agonists N6-Cyclohexyladenosine (CHA, A1-agonist) and 5'-(N-ethylcarboxamido)-adenosine (NECA, A2-agonist) on the force of contraction (Fc) and effective refractory period (ERP) of isolated guinea pig papillary muscle were measured. Additionally, the influence of potent cycloxygenase inhibitor indomethacin on above mentioned parameters as well as on the effects of CHA and NECA were studied. It was found that CHA induced negative inotropic action and a shortening of ERP, opposite to NECA and indomethacin. The pretreatment with 10 microM of indomethacin shifted to the right the CHA effects and abolished the NECA effects.