Pharmacology of Casimiroa edulis; II. Cardiovascular effects in the anesthesized dog

The cardiovascular effects of an aqueous extract of seeds of Casimiroa edulis were assessed in pentobarbital-anesthetized dogs. The extract produced marked hypotension which lasted more than two hours; it was accompanied by moderate and less persistent bradycardia. The histaminergic nature of these effects was investigated in animals pretreated with the specific antagonists diphenhydramine, cimetidine, or a combination of both agents. These experiments showed that both H1- and H2-receptors were involved in the hypotensive response, while the bradycardia was mediated solely through an H1-mechanism. In open-chest dogs instrumented for recording cardiac output (ascending aortic flow), left ventricular contractility (dp/dt), central venous pressure (superior vena cava), systemic blood pressure, heart rate, total peripheral resistance and stroke volume, the extract decreased blood pressure and peripheral resistance and increased cardiac output and stroke volume, without modifying the other parameters. It was concluded that the cardiovascular pattern of Casimiroa edulis in the dog is that of a peripheral arterial vasodilator and that it increases cardiac output by reducing left ventricular afterload.