title: (+)Naloxone potentiates the inotropic effect of epinephrine in the isolated dog heart.
abstract: Naloxone potentiates the inotropic effect of circulating catecholamines in the isolated canine heart. The stereospecificity of this response was evaluated with the aid of the less active (+)enantiomer of naloxone. The more common (-)isomer of naloxone increased the contractile response to epinephrine only at the higher dose tested (4 mg). This effect of naloxone was not observed at a tenfold lower dose (0.4 mg), indicating a very narrow dose-response range. (+)Naloxone was effective at the lower dose and was, therefore, equal to or better than (-)naloxone in potentiating the inotropic effect of epinephrine. When introduced afterward, (-)naloxone did not add to the effect of (+)naloxone. These data suggest that naloxone modifies cellular responsiveness to catecholamines through a nontraditional opiate receptor, through a nonopiate receptor, or through a nonreceptor mechanism.
authors.affiliation: Department of Physiology, Texas College of Osteopathic Medicine, Fort Worth 76107.
authors.forename: H
authors.initials: H
authors.lastname: Gu
authors.forename: B A
authors.initials: BA
authors.lastname: Barron
authors.forename: J F
authors.initials: JF
authors.lastname: Gaugl
authors.forename: J L
authors.initials: JL
authors.lastname: Caffrey
mesh_terms: D000818:Animals; D004285:Dogs; D004357:Drug Synergism; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009270:Naloxone / Q000494:pharmacology*; D013237:Stereoisomerism; D013268:Stimulation, Chemical
chemical_list: D009270:Naloxone; D004837:Epinephrine