Positive Chronotropic and Negative Inotropic Actions of Vasopressin in Isolated Blood-Perfused Canine Atrium

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Abstract
Effects of vasopressin on SA [sino-atrial] 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. Vasopressin appears to have a direct stimulating property on SA nodal pacemaker activity and a direct suppressive property on atrial contractility. [Vasopressin-induced myocardial ischemia was previously shown to lead to severe reactions and even death.].