Hoffmann P, Thorén P
Department of Physiology, University of Göteborg, Sweden.
Acta Physiol Scand. 1988 Jun;133(2):211-9. doi: 10.1111/j.1748-1716.1988.tb08400.x.
The influence of prolonged low-frequency, low-intensity electric stimulation of the gastrocnemius muscle or of the biceps femoris muscle on blood pressure and heart rate was investigated in unanaesthetized, spontaneously hypertensive rats (SHR). In both groups, elevations of blood pressure and heart rate were elicited during the 60 min of muscle stimulation. After cessation of the stimulation, a depressor response developed within 60 min. Thirty to sixty minutes post-stimulation the fall in blood pressure was 19 +/- 3 and 17 +/- 4 mmHg, respectively (mean +/- SE) compared with controls. In both groups, the depressor response lasted for over 5 h. In addition, the gastrocnemius-stimulated animals also developed a post-stimulatory bradycardia. In one group of SHR the sciatic nerve was anaesthetized with bupivacaine. The arousal response during stimulation was similar to that in the other groups, but after termination of stimulation blood pressure returned to the control level without any further drop. To investigate further the neurotransmitters involved, one group of gastrocnemius-stimulated SHR was given naloxone by infusion during the stimulation. A modest post-stimulatory blood pressure fall also occurred in this group, but it lasted only 90 min. Another SHR group was pre-treated with parachlorophenylalanine, a serotonin synthesis blocker, which completely abolished the post-stimulatory depressor response. These results indicate that prolonged muscle stimulation gives rise to a post-stimulatory long-lasting drop in blood pressure and that this response is mediated by somatic nerve afferents. Involvement of the endorphin and serotonin systems is also suggested.
在未麻醉的自发性高血压大鼠（SHR）中，研究了长时间低频、低强度电刺激腓肠肌或股二头肌对血压和心率的影响。在两组中，肌肉刺激的60分钟内血压和心率均升高。刺激停止后，60分钟内出现降压反应。与对照组相比，刺激后30至60分钟血压下降分别为19±3和17±4 mmHg（平均值±标准误）。在两组中，降压反应持续超过5小时。此外，接受腓肠肌刺激的动物在刺激后还出现了心动过缓。在一组SHR中，用布比卡因麻醉坐骨神经。刺激期间的唤醒反应与其他组相似，但刺激终止后血压恢复到对照水平，没有进一步下降。为了进一步研究涉及的神经递质，在刺激期间对一组接受腓肠肌刺激的SHR通过输注给予纳洛酮。该组也出现了适度的刺激后血压下降，但仅持续90分钟。另一组SHR用对氯苯丙氨酸（一种血清素合成阻滞剂）预处理，这完全消除了刺激后的降压反应。这些结果表明，长时间的肌肉刺激会导致刺激后血压长期下降，并且这种反应是由躯体神经传入介导的。还提示内啡肽和血清素系统参与其中。
