THE PHYSIOLOGICAL RÔLE OF THE CORONARY CONSTRICTOR FIBRES. I. THE EFFECT OF THE CORONARY VASOMOTORS ON THE SYSTEMIC BLOOD PRESSURE

¹ Institute of Physiology, Medical University of Debrecen, Hungary

On dogs under morphine-chloralose narcosis the coronary constrictors are tonically active: after pharmacological or surgical blocking of this tone coronary flow increases, resistance decreases.

The augmentation of the general sympathetic tone by clamping of the common carotids increases the coronary resistance. After interruption of the constrictor pathways this increase in the resistance did not occur. The augmented tonic activity of the coronary constrictors or the coronary constriction induced by vasopressin or noradrenaline leads to a reflex fall of the blood pressure. After vagotomy this reflex fall induced by increased tension of the vessel walls fails to occur. From the data presented the conclusion may be drawn that an important physiological rôle of the coronary constrictors is to maintain coronary flow (i.e. O₂ consumption) on an optimum level by restraining flow increase under conditions of augmented work load of the heart on the one hand, and to impede by reflex means a too great increase of the coronary perfusion pressure on the other.