THE PHYSIOLOGICAL RÔLE OF CORONARY CONSTRICTOR FIBRES. II. THE RÔLE OF CORONARY VASOMOTORS IN METABOLIC ADAPTATION OF THE CORONARIES

¹ Institute of Physiology, Medical University, Debrecen, Hungary

On dogs under morphine-chloralose narcosis the reactive-hyperæmia test was used to evaluate the metabolic adaptation of the coronary circulation.

When coronary constrictor tone was increased by clamping one or both carotids, the degree of hyperæmic responses was also increased, as compared to the reactions of the control period. By pharmacological or surgical interruption of the coronary vasomotor pathways a diminution or total disappearance of the hyperaemic responses could be observed. When the hyperaemic responses were eliminated, the intracoronary administration of vasopressin restored the tone of the vessel walls and thereby the capacity of the coronaries to adapt themselves to metabolic demands. All this indicates that the preliminary constrictor tone is an essential condition for the metabolic adaptation of the coronaries. Thus the vasomotor constrictor tone of the coronaries serves as a "reserve" of this adaptation. If this "reserve" is diminished disturbances can be observed in the lumen adjusting capacity of the coronaries as well as in the O₂ consumption of the heart under condition of increased heart activity.

The experimental data indicate that the unresponsiveness of the coronaries to metabolic stimuli is probably due to a rigidity of the vessels. This coronary "rigidity" is considered as a phenomenon equivalent to the human angina pectoris.