title: Temperature-dependent effects of morphine on the isolated right atrium.
abstract: The aim of the present study was to examine whether changes in temperature alter the effects of morphine on isolated right atria. Morphine dose-response curves at different temperatures (30, 37 or 40 degrees C) from right atria of the rat were obtained. The maximal negative chronotropic effect induced by morphine was 11 +/- 3% at 37 degrees C and 20 +/- 1% at 30 degrees C. However, when the temperature was increased to 40 degrees C, morphine induced a positive chronotropic effect. The increase in auricular automaticity induced by morphine at 40 degrees C was antagonized in the presence of naloxone (5 x 10(-6) mol/l). These data demonstrated that: (1) hyperthermia modifies the effects of morphine on isolated right atria and (2) at 40 degrees C morphine induces a positive chronotropic effect by activation of opioid receptors.
authors.affiliation: Department of Physiology and Pharmacology, Murcia University School of Medicine, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Ruiz
authors.forename: M I
authors.initials: MI
authors.lastname: Valcarcel
authors.forename: M L
authors.initials: ML
authors.lastname: Laorden
mesh_terms: D000818:Animals; D016280:Atrial Function, Right / Q000187:drug effects; D003080:Cold Temperature; D003864:Depression, Chemical; D005260:Female; D006325:Heart Atria / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D009270:Naloxone; D009020:Morphine