[Effects of continuous infusion of vasopressin on circadian rhythms of food and water intake, urine output and electrolyte excretion in Brattleboro rats].

Food intake (FI), water intake (WI), urine output (UO), Na+ and K+ excretions were investigated for 2 days at 4-h intervals during continuous infusion of saline or vasopressin (VP) 1.0 UI/day, in male Brattleboro vasopressin-deficient rats. Continuous VP infusion reduced significantly 24-h amounts of WI and UO, and increased Na+ excretion. A significant (3.5 h) phase advance of the circadian rhythm of WI was observed, while the group circadian rhythm of Na+ excretion was eliminated due to irregular phase shifts in the different rats. The results suggest that VP do not play a role in the generation of the circadian rhythms of water input and output, but it may participate in their internal synchronization.