Positive chronotropic and negative inotropic actions of vasopressin in isolated blood-perfused canine atrium.

Effects of vasopressin on SA nodal pacemaker activity and atrial contractility were investigated, using 5 isolated, blood-perfused canine atrium preparations. Vasopressin produced a dose-related positive chronotropic and negative inotropic effect, which was not influenced by treatments with an adequate dose of atropine or an adrenergic beta-blocking agent, alprenolol. From these results, it is concluded that vasopressin has a direct stimulating property on SA nodal pacemaker activity and a direct suppressive property on atrial contractility.