Abstract
Many investigators have observed that the coronary blood flow was markedly increased following the stimulation of the stellate ganglia and/or their cardiac branches. But as in previous report of our clinic pointed out, it cannot be concluded that the sympathetic nerve dilate the coronary vessels directly. From recent work of our clinic, it seems to be that the sympathetic nerve constricts the coronary vessels, and that the augmentation of coronary blood flow following the sympathetic stimulation chiefly results from the hemodynamic and metabolic changes induced. On the other hand, many workers suspected that the metabolites of the heart muscle released following the stimulation of the sympathetic nerve dilated the coronary vessels. It is the purpose of present study to find out some vasodilatative substance in coronary venous blood, to clarify the nature of the sympathetic coronary vasodilatative effect.The outline of experimental method was almost the same as previous report. The left coronary artery of dog was perfused from the animal's own femoral artery. Then the peripheral ends of the cut stellate ganglia or vagal nerve were stimulated electrically and the coronary venous blood samples were obtained before, during and after the stimulation of the nerves. The blood samples were obtained six times in one experiment : before stimulation, during stimulation and 15 seconds, 1 minute, 2 minutes, 3 minutes after the stimulation. Then immediately one ml. of those blood samples were injected into the tubing leading to the coronary artery as in previous report performed.Results were as follows : 1. Coronary blood flow was markedly augmented after the injection of the coronary venous blood samples which were obtained during the stimulation of the sympathetic nerves or 15 seconds thereafter. On the other hand, the injection of the coronary venous blood samples obtained before stimulation or 1 minute or more thereafter did not augmented the coronary blood flow. In 6 among 11 cases such findings were observed. No significant changes of heart rate and blood pressure was observed after the intracoronary artery injection of coronary venous blood samples.2. The coronary blood samples obtained before, during, or after the stimulation of the vagal nerve did not affect coronary blood flow, heart rate and blood pressure.3. From this study, it is obvious that the coronary venous blood samples, which were obtained during the stimulation of the sympathetic nerve or 15 seconds thereafter, induced coronary vasodilatation. Since no remarkable hemodynamic changes were observed following the intracoronary artery injection of coronary venous blood samples, it is concluded that some vasodilatative substance present in those effective blood samples. It seems that this substance plays an important role in sympathetic coronary vasodilatation. The exact nature of this substance is not clear, but it is probably some metabolite, because the effective coronary venous blood samples were obtained during the time corresponding to the increase in vigor of cardiac contraction. The coronary flow patterns following the intracoronary artery injection of coronary venous blood samples were far different from those following the injection of epinephrine or norepinephrine, and therefore at least coronary vasodilatative substance thus demonstrated is not epinephrine or norepinephrine themselves.
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