Antidiuretic effect of beta-endorphin and morphine in Brattleboro rats: development of tolerance and physical dependence after chronic morphine treatment.
1 beta-Endorphin (2 micrograms injected into the lateral ventricles) produced a significant decrease in the urine outflow and in the excretion of Na+ and K+ in Brattleboro rats, animals suffering from severe diabetes insipidus. Morphine intracerebrally also produced antidiuresis, as compared to saline-treated controls. 2 Morphine injected intraperitoneally caused a dose-dependent decrease in the urine outflow, and in the excretion of Na+ and K+. 3. Rats chronically treated with morphine (72 h of morphine pellet implantation) were less sensitive to the antidiuretic effect of a challenge dose of morphine than control Brattleboro rats implanted with placebo pellets, but otherwise treated similarly. 4 After chronic morphine administration, Brattleboro rats became dependent on morphine. Challenge with 1 mg/kg naloxone (s.c.) precipitated an abrupt opiate withdrawal syndrome characterized, among other symptoms, by increased urination in contrast to the antidiuresis observed before naloxone.
D000818:Animals; D003919:Diabetes Insipidus / Q000503:physiopathology; D004231:Diuresis / Q000187:drug effects*; D004361:Drug Tolerance; D004723:Endorphins / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology; D009318:Natriuresis / Q000187:drug effects; D011188:Potassium / Q000652:urine; D051381:Rats; D001615:beta-Endorphin
D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin; D009020:Morphine; D011188:Potassium