Henning R J, Cheng J, Levy M N
Division of Investigative Medicine, Mt. Sinai Medical Center, Cleveland, Ohio.
Am J Physiol. 1989 Feb;256(2 Pt 2):H428-33. doi: 10.1152/ajpheart.1989.256.2.H428.
We determined the effects of vagal stimulation on the time constant (tau) of left ventricular isovolumic pressure decay and on the maximum rates of left ventricular pressure change (dP/dt) during contraction and relaxation in anesthetized dogs. In each dog, the atria were paced at a constant rate of 150 beats/min. We recorded left ventricular pressure waveforms in the absence (control) and in the presence of vagal stimulation at frequencies of 1, 2, and 3 Hz. During the control periods and during vagal stimulation at each frequency, we determined tau, the maximal rate of contraction, and the maximal rate of relaxation from left ventricular pressure waveforms recorded at medium (100 mmHg), high (130 mmHg), and low (73 mmHg) afterloads. Vagal stimulation at a frequency of 3 Hz increased tau by 23%. This effect of vagal stimulation on tau was most pronounced at the high afterload. Vagal stimulation at 3 Hz decreased the maximal rate of relaxation by 19%, but it decreased the maximal rate of contraction by only 8%. Thus vagal stimulation significantly decreased the rate of left ventricular relaxation and had a greater depressant effect on ventricular relaxation than on contraction.
我们测定了迷走神经刺激对麻醉犬左心室等容压力衰减时间常数（tau）以及收缩和舒张过程中左心室压力变化最大速率（dP/dt）的影响。在每只犬中，心房以150次/分钟的恒定速率起搏。我们记录了在无迷走神经刺激（对照）以及迷走神经刺激频率为1、2和3Hz时的左心室压力波形。在对照期以及每个频率的迷走神经刺激期间，我们从中等（100mmHg）、高（130mmHg）和低（73mmHg）后负荷下记录的左心室压力波形中测定tau、最大收缩速率和最大舒张速率。3Hz频率的迷走神经刺激使tau增加了23%。迷走神经刺激对tau的这种影响在高后负荷时最为明显。3Hz的迷走神经刺激使最大舒张速率降低了19%，但仅使最大收缩速率降低了8%。因此，迷走神经刺激显著降低了左心室舒张速率，并且对心室舒张的抑制作用大于对收缩的抑制作用。
