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Ventricular responses of a few catecholamines in rabbits were studied with the use of various parameters: blood pressure, systemic output or stroke volume, heart rate, ventricular contractile force and change of segment length of ventricular muscle. In recording ventricular contraction, two kinds of apparatus, strain gauge compass and arch, which we devised, were used. Simultaneous recordings of these various factors permit characterization and direct comparison of the nature and sequence of left ventricular responses by infusion of catecholamines. Epinephrine or norepinephrine, in smaller dose produced almost the same changes in ventricular contractile force and segment length of ventricular muscle. However, in the course of a short time after the administration of the large dose of these drugs, the change of coutractile force by means of strain gauge arch was significant, but the change of muscle segment length measused by means of strain gauge compass was more complicated and gave us much information of cardiac function. Namely, there were a decrease of stroke deflection with a decrease of stroke volume and a downward displacement of systolic and diastolic excursion curve which meant heart dilatation. By the administration of methoxamine, the changes of muscle segment length were more marked than the changes of contractile force. By the administration of isoproterenol, the changes of contractile force were more marked than the changes of muscle segment length changes. The use of such two kinds of strain gauge apparatus may be valuable for observing the cardiac performance more precisely.

Investigation of the cardiovascular action of sympathetic amines using two kinds of strain gauge instrument.