title: Effects of acute administration of morphine on right atrial catecholamine content and heart rate in chronically morphine-treated rats.
abstract: The purpose of this study was to determine if chronic administration of the preferential mu agonist, morphine, induced changes in cardiac catecholamine content. In rats treated with morphine for 7 days, a challenge dose of morphine 30 mg kg-1 i.p. increased atrial noradrenaline (mean 1123.8 (SEM 62.2) ng g-1), adrenaline (79.48 (8.5) ng g-1) and dopamine (46.0 (1.0) ng g-1) content whereas dopamine turnover was decreased; this was accompanied by a decrease in the frequency of contraction of the isolated right atria. There were no changes in noradrenaline, adrenaline, dihydroxy phenylacetic acid (DOPAC) or DOPAC:dopamine ratio in placebo-treated rats. These results demonstrated that acute administration of morphine in morphine-treated rats produced inhibition of neuronal catecholamine activity in the heart which could be responsible for the decrease in atrial contraction frequency.
authors.affiliation: Department of Physiology and Pharmacology, University School of Medicine, Murcia, Spain.
authors.forename: J V
authors.initials: JV
authors.lastname: Rabadan
authors.forename: M V
authors.initials: MV
authors.lastname: Milanés
authors.forename: M L
authors.initials: ML
authors.lastname: Laorden
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D046508:Culture Techniques; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009206:Myocardium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000701:Analgesics, Opioid; D002395:Catecholamines; D009020:Morphine