ObjectiveTo determine the pharmacologic effect of carcinine (beta-alanyl histamine), a compound that has been shown to be a positive inotrope in the isolated perfused guinea pig heart, on hemodynamics in an intact, anesthetized rat model.DesignProspective dose-response study.SettingAnimal research laboratory of a university medical center.SubjectsMale Sprague-Dawley rats.InterventionsEight male Sprague-Dawley rats were anesthetized with ketamine and midazolam. A tracheostomy tube, and central venous and arterial catheters were inserted. An electromagnetic flow probe was placed around the ascending aorta through a right thoracotomy for measurement of cardiac output. Dosages of carcinine from 0 to 10 mg/kg were infused intravenously over 30 secs, and hemodynamic parameters were measured at baseline and at peak effect.Measurements and Main ResultsAt dosages of 3 mg/kg and 10 mg/kg, carcinine significantly reduced mean arterial blood pressure, systemic vascular resistance index, and left ventricular stroke work index. There was no carcinine-induced effect on heart rate, central venous pressure, cardiac index, or stroke index. Lower doses of carcinine had no effect on the measured variables.ConclusionsIn this open-chest rat model, the primary pharmacologic effect of carcinine is systemic arterial vasodilation. A negative inotropic effect is suggested. Hypotension is secondary to these carcinine-induced actions. These results differ from results previously published using an isolated guinea pig heart preparation. Our model suggests that efforts to develop a clinical role for carcinine should exploit vascular rather than cardiac effects. Species differences may also play a role. (Crit Care Med 1996; 24:2042-2045)