Role of ADH in ethylketocyclazocine-induced diuresis: studies in the Brattleboro rat.

Kappa opioids produce diuresis presumably through ADH. We investigated further the role of ADH in kappa-induced diuresis by utilizing the Brattleboro rat, a strain lacking endogenous ADH. Ethylketocyclazocine (EKC), a kappa opioid prototype, increased urine formation in Sprague-Dawley, but not in Brattleboro rats. Furthermore, EKC pretreatment abolished the antidiuretic response to ADH administered exogenously to Brattleboro rats. Our study suggests that, in addition to a fall in plasma ADH reported previously, kappa opioids have direct effects on the renal response to ADH.