title: Morphine sulfate depression of cardiac function is attenuated by opiate receptor antagonism with naloxone.
abstract: In previous work, morphine sulfate was shown to decrease heart rate (HR) and cardiac output (CO) in a dose-related fashion. It was hypothesized that this effect was mediated by opiate receptors located in the myocardium. The present study evaluated the effect of opiate receptor antagonism with naloxone using a modified Langendorff rat heart perfusion apparatus. Sixty-five rat hearts were excised and perfused with Krebs-Henseleit buffer (KHB) solution, to which morphine sulfate and naloxone (NAL) were added in different concentrations. In the initial studies, NAL (10(-5) M) was added to the perfusate prior to the incremental additions of morphine. This resulted in no antagonism of the previously described opiate agonist effects. Norepinephrine (NE; 10(-9) M) was then added to the perfusate prior to the NAL or morphine. The NE did not affect the dose-related decrease in HR and CO when morphine was added but did permit the attenuation of the morphine effect by the addition of increasing concentrations of NAL up to 10(-5) M. These results suggest that the agonist effect can be attenuated by opiate receptor antagonism with NAL; the data also suggest a possible interrelationship between opiate and catecholamine receptor activity in the myocardium.
authors.affiliation: Department of Surgery, West Virginia University, School of Medicine, Morgantown 26506.
authors.forename: T
authors.initials: T
authors.lastname: Vargish
authors.forename: K C
authors.initials: KC
authors.lastname: Beamer
authors.forename: T
authors.initials: T
authors.lastname: Daly
authors.forename: T R
authors.initials: TR
authors.lastname: Riggs
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D009020:Morphine / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects*
chemical_list: D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine