冠循環の神経性調節に関する研究(第3報) : 迷走神経末梢端刺戟による冠流血量の変化

In the present patper, the effects of the stimulation of the peripheral end of the vagal nerve were reported, with consideration of the relationship between vasomotor and hemodynamic factors. Experimental methods were same as already described in the Part I of this study.Results were as follows : 1) Stimulations of the peripheral ends of the cut vagal nerves were performed, on the left side in 15 experiments on 11 dogs, on the right side in 4 experiments on 4 dogs. During the stimulation of the vagal nerve, the depression of the blood pressure and the bradycardia occurred in all experiments.2) Coronary blood flow decreased with the depression of the blood pressure, for example, as shown in Fig. 1. But, in about a half cases of all experiments, coronary blood flow increased initially for a short time, and then decreased with marked depression of the blood pressure, for example, as shown in Fig. 2 and 3. Experimental results of all cases in the initial increase and maximal decrease in coronary blood flow, were shown in Tab. I and II, respectively.3) Coronary vascular resistance decreased markedly during phases of the initial increase in coronary blood flow (white dots in Fig. 4). In addition, it decreased also during phases of the maximal decrease in coronary blood flow, in over a half cases of experiments (black dots in Fig. 4). Changes in coronary vascular resistance in the vagal nerve stimulation (Fig. 4) were quite different from that in the depressor response by the stimulation of the proximal end of the vagal nerve (Fig. 5) (already discussed in Part I of this study). It suggests coronary vasodilatory actions by the stimulation of the peripheral end of the vagal nerve.4) It seems likely that, the more decreases the heart rate, the more decreases the coronary vascular resistance, when the degree of the bradycardia is not over approximatery 40 %, but, in marked bradycardia, the coronary vascular resistance tended to increase, as shown in Fig. 6.The initial increase in coronary blood flow (white dots in Fig. 6), however, occurred with either very slight or marked bradycardia, in spite of depression of the blood pressure. It suggests the vagal active vasodilatation.5) From results reported in this paper, it may be concluded that ; the vagal nerve stimulation produces the coronary vosodilation and the initial increase in coronary blood flow ; but, the coronary blood flow decreases thereafter, or throughout during the stimulation from its beginning, because of the marked depression of the blood pressure ; the bradycardia itself may have some vasodilatatory effects on the coronary blood flow.