Ford T W, McWilliam P N
J Physiol. 1986 Nov;380:341-7. doi: 10.1113/jphysiol.1986.sp016289.
The bradycardia evoked by electrical stimulation of the peripheral end of the rabbit vagus nerve is mediated by both myelinated and non-myelinated fibres. Stimulation of myelinated fibres at 5 Hz for 20 s resulted in a fall in heart rate from a control value of 204 +/- 1.3 to 182 +/- 1.2 beats min-1 (means + S.E. of means). On stimulation of both myelinated and non-myelinated fibres, heart rate fell to 169 +/- 2.1 beats min-1. Heart rate returned rapidly to control value following stimulation of myelinated fibres but only slowly after stimulation of both myelinated and non-myelinated fibres. Thus recruitment of non-myelinated fibres increased both the magnitude and duration of the bradycardia. Atropine abolished all effects of vagal stimulation on heart rate. Hexamethonium abolished the effect of myelinated fibres on heart rate; however, recruitment of non-myelinated fibres still produced a bradycardia. It is suggested that the prolonged effect following stimulation of non-myelinated fibres may reflect the persistent action of a non-cholinergic excitatory transmitter at the ganglion.
电刺激兔迷走神经外周端所诱发的心动过缓是由有髓纤维和无髓纤维共同介导的。以5Hz频率刺激有髓纤维20秒，可使心率从204±1.3次/分钟的对照值降至182±1.2次/分钟（均值±均值标准误）。同时刺激有髓纤维和无髓纤维时，心率降至169±2.1次/分钟。刺激有髓纤维后心率迅速恢复到对照值，但同时刺激有髓纤维和无髓纤维后心率恢复缓慢。因此，无髓纤维的募集增加了心动过缓的幅度和持续时间。阿托品可消除迷走神经刺激对心率的所有影响。六甲铵可消除有髓纤维对心率的影响；然而，无髓纤维的募集仍会导致心动过缓。有人认为，刺激无髓纤维后出现的延长效应可能反映了神经节处一种非胆碱能兴奋性递质的持续作用。
