Antidiuretic effect of acute morphine administration in the conscious rat

Morphine was administered intravenously to normal and to Brattleboro (genetically deficient in antidiuretic hormone) rats. The injection caused a significant decrease in mean arterial pressure and urine flow in all animals, including those homozygous for diabetes insipidus. It is suggested that the antidiuretic effect of morphine may occur independently of ADH release.