Characterization of the opioid receptor subtypes mediating the negative inotropic effects of DAMGO, DPDPE and U-50, 488H in isolated human right atria strips.

The present investigation was aimed at elucidating if mu-, delta- and kappa-opioid receptors are involved in the effects of DAMGO (selective mu-agonist), DPDPE (selective delta-agonist) and U-50,488H (selective kappa-agonist) in isolated electrically driven human right atria strips. The negative inotropic effects induced by the opioid agonists used in this study were not antagonized in presence of naloxone (preferentially mu-antagonist), naltrindole (selective delta-antagonist) and norbinaltorphimine (selective kappa-antagonist). These data suggest that the opioid receptors are not involved in the cardiac depressant effects induced by mu-, delta- and kappa-opioid agonists.