title: Cardiovascular changes during morphine withdrawal in the rat: effects of clonidine.
abstract: Arterial blood pressure and heart rate were measured in unrestrained rats as an index of the autonomic component of the morphine withdrawal syndrome. Physical dependence was produced by a constant infusion of morphine at increasing doses over 7 days. Signs of physical dependence observed during abrupt withdrawal included classical behavioral symptoms such as withdrawal body shakes (WBS) and increased autonomic responsiveness which was indicated by a sustained increase in mean arterial pressure (MAP) up to 23 mmHg. Injection of naloxone in morphine dependent rats also evoked a dose-related increase in MAP to about 40 mmHg. The antiwithdrawal effects of clonidine were tested in this model by pretreating dependent rats with this agent (6-60 micrograms/kg). Clonidine inhibited the pressor response produced by naloxone by 23-60%. These findings indicate that the increase in MAP during opiate withdrawal provides an objective and quantitative index of the intensity of the narcotic withdrawal syndrome in dependent rats.
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006801:Humans; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000139:chemically induced / Q000503:physiopathology*
chemical_list: D009270:Naloxone; D009020:Morphine; D003000:Clonidine