Aars H, Myhre L, Haswell B A
Acta Physiol Scand. 1978 Jan;102(1):84-93. doi: 10.1111/j.1748-1716.1978.tb06048.x.
The participation of aortic nerve C fibers in the baroreflex was investigated by recording changes in renal nerve activity in response to acute increases in arterial pressure, in two experimental situations: with the A and C fibres of the aortic nerve intact, and with the A fibres temporarily blocked by a hyperpolarizing current (anodal block). Pressure was increased by manual inflation of an intra-aortic balloon, and interference from other barorecptor areas was avoided by carotid occlusion and sectioning of the right aortic nerve. Rises in mean arterial pressure exceeding 20 mmHg, to levels above 110 mmHg, were needed to trigger sympathetic inhibition via C fibres. A rise of 45 mmHg caused 50% reduction in sympathetic activity, equal to that obtained by stimulation of aortic nerve C fibres at about 3 Hz. In contrast, a rise of 20-30 mmHg evoked more than 60% reduction in sympathetic activity when the A fibres were operative. Judged by these studies of peak reflex responses to brief pressure rises, baroreceptors with C fibres in the aortic nerve have a much higher threshold to pressure than their myelinated counterpart; the C fibres contribute to the baroreflex inhibition sympathetic discharge only when pressure is increased well above normal resting levels.
通过记录肾神经活动的变化，以研究主动脉神经C纤维在压力感受性反射中的作用。该变化是在两种实验情况下，对动脉压急性升高的反应：一种是主动脉神经的A和C纤维完整无损，另一种是A纤维被超极化电流（阳极阻滞）暂时阻断。通过手动向主动脉内球囊充气来升高压力，并通过颈动脉闭塞和切断右主动脉神经来避免其他压力感受器区域的干扰。平均动脉压升高超过20 mmHg，达到110 mmHg以上的水平，才能通过C纤维触发交感神经抑制。45 mmHg的升高导致交感神经活动降低50%，这与以约3 Hz的频率刺激主动脉神经C纤维所获得的降低程度相当。相比之下，当A纤维起作用时，20 - 30 mmHg的升高会引起交感神经活动降低超过60%。根据这些对短暂压力升高的峰值反射反应的研究判断，主动脉神经中具有C纤维的压力感受器对压力的阈值比其有髓鞘的对应物高得多；只有当压力升高到远高于正常静息水平时，C纤维才会对压力感受性反射抑制交感神经放电起作用。
