Vasopressin V1-receptor blockade lowers arterial blood pressure in young conscious Long-Evans rats.

Young, conscious Long-Evans rats had significantly higher basal mean arterial blood pressure than age-matched Brattleboro rats with hereditary hypothalamic diabetes insipidus, and an intravenous injection of a specific vasopressin V1-receptor blocker significantly decreased the mean arterial pressure in the former animals only. The basal heart rate, which was significantly higher in the Brattleboro rats than in the Long-Evans rats, was unaffected by the vasopressin antagonist in either strain. These results indicate that vasopressin may be important in maintaining normal blood pressure in young rats.