Eldridge F L
Respir Physiol. 1980 Mar;39(3):327-43. doi: 10.1016/0034-5687(80)90064-x.
The phrenic nerve response to identical carotid sinus nerve (CSN) stimulations was studied in anesthetized, paralyzed and vagotomized cats during apnea induced by hypocapnia. Apnea could be terminated and rhythmic phrenic activity reestablished by CSN stimulation. Magnitudes and latencies of the phrenic response were used as indices of the level of subthreshold respiratory neural activity before stimulation. Increasing hypocapnia progressively reduced the apparent magnitude of the response to a constant CSN stimulus and increased the latency. When the chemical stimulus (PCO2) was held constant at levels subthreshold for rhythmic respiration, it was found that: (1) physical calf muscle stimulation shortened the latency, (2) restimulation of the CSN led to greater magnitudes of response and shorter latencies as the time after a prior stimulation became shorter. The findings support a conclusion that even in the absence of rhythmic respiration there exists a subthreshold respiratory drive which is graded by the level of PCO2 and which is affected by neural input from limb muscles and by the mechanism that causes respiratory afterdischarge.
在低碳酸血症诱发的呼吸暂停期间，对麻醉、麻痹和切断迷走神经的猫，研究了膈神经对相同颈动脉窦神经（CSN）刺激的反应。通过CSN刺激可终止呼吸暂停并重新建立膈神经的节律性活动。膈神经反应的幅度和潜伏期被用作刺激前阈下呼吸神经活动水平的指标。低碳酸血症程度加重会逐渐降低对恒定CSN刺激的反应的表观幅度，并延长潜伏期。当化学刺激（PCO2）维持在低于节律性呼吸阈值的水平时，发现：（1）对小腿肌肉进行物理刺激可缩短潜伏期，（2）随着前一次刺激后时间的缩短，再次刺激CSN会导致更大的反应幅度和更短的潜伏期。这些发现支持这样一个结论，即即使在没有节律性呼吸的情况下，也存在一种阈下呼吸驱动，其由PCO2水平分级，并受来自肢体肌肉的神经输入以及导致呼吸后放电的机制影响。
