EFFECTS OF MORPHINE ON ATRIAL PREPARATIONS OBTAINED FROM NONFAILING AND FAILING HUMAN HEARTS

We have examined the effects of morphine in auricular myocardium from non-failing and failing human hearts. In both preparations morphine in duced inhibition. These responses were not antagonized by naloxone. Co mparison of mean IC30 values obtained in non-failing (3.9 (SEM 0.2) x 10(-8) mol litre(-1)) and failing (5010 (200) x 10(-8) mol hearts indi cated that the morphine concentration-response curves were significant ly (P < 0.001) shifted to the right in preparations from failing heart s. In addition, a decrease in the maximal response was observed. These data indicate that opioid receptors are not involved in the cardiac e ffects induced by morphine and that there is a decrease in responses t o morphine in the failing heart.