title: Morphine effects on the cardiovascular system of awake, freely behaving rats.
abstract: The effects of small, i.v. infusion of morphine on the heart rate was studied in unanesthetized rats. A dose-response study indicated that all values of morphine between 5 and 1000 mug/kg resulted in a transient bradycardia. In addition, morphine doses above 20 mug/kg induced cardiac irregularities including atrial fibrillation, atrioventricular block and temporary cardiac arrest. When morphine was delivered daily over a period of eight weeks, cardiac responding (first arrhythmias and then the bradycardia) became tolerant at a time when catatonia was still present. These results indicate that in an unanesthetized rat, profound cardiovascular effects are seen to very small, mug range, doses of morphine.
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D003864:Depression, Chemical; D004361:Drug Tolerance; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D051381:Rats; D013997:Time Factors
chemical_list: D009020:Morphine