Evidence for a depressor reflex elicited from left ventricular receptors during occlusion of one coronary artery in the cat.

Circulatory responses to shortlasting occlusions of one coronary artery (left anterior descendent or right coronary artery) were studied in chloralose-anesthetized cats. — When the carotid sinus baroreceptors were left functionally intact, coronary occlusion induced moderate reflex reductions of heart rate and blood pressure and slight increases of resistance and capacitance vessel tone in the calf muscles. When the buffering influences from the baroreceptors were largely eliminated by bilateral carotid occlusion, the reflex fall of blood pressure and heart rate became more pronounced and a clearcut vasodilatation was now observed. After cold block of the cervical vagi, the blood pressure fall upon coronary obstruction was markedly diminished, the heart rate response was reversed to a slight tachycardia and a marked peripheral vasocon-striction ensued. After i.v. administration of local anesthetics (lidocaine 3–4 mg/kg b.wt.) the reflex response to coronary obstruction and to shortlasting occlusions of the ascending aorta were almost completely eliminated. — It is concluded that acute occlusions of one coronary artery induce a reflex bradycardia and vasodilatation, in all probability due to activation of left ventricular mechanoreceptors. The vascular responses in this inhibitory reflex seem to be significantly moderated by influences from the arterial baroreceptors.