Pisarri T E, Yu J, Coleridge H M, Coleridge J C
Respir Physiol. 1986 Apr;64(1):29-43. doi: 10.1016/0034-5687(86)90058-7.
Vagal cooling experiments suggest that the deep slow breathing observed after vagotomy results not only from loss of pulmonary stretch receptor feedback, but also from loss of some unidentified vagal input. To investigate this possibility we cooled the vagus nerves in anesthetized dogs. In dogs breathing spontaneously, the Hering-Breuer reflex was abolished at 7 degrees C, but average expiratory time was unchanged and lengthened only on cooling below 3 degrees C. In artificially ventilated dogs the pulmonary vagus nerves were cooled in the chest and phrenic activity was recorded. Entrainment of phrenic bursts to the ventilator cycle ceased at 7 degrees C, and expiratory pauses shortened; they lengthened again on cooling below 3 degrees C. Cervical vagotomy did not change breathing pattern after the pulmonary vagus nerves were cut. Recording of afferent impulses during cooling showed that at 5 degrees C or less pulmonary vagal input was confined largely to nonmyelinated fibers; at 3 degrees C, background activity in pulmonary C-fibers was still 78% of control whereas myelinated afferents were virtually silent. We suggest that in eupnea low frequency, background activity in pulmonary afferent C-fibers shortens expiratory time.
迷走神经冷却实验表明，迷走神经切断术后观察到的深度慢呼吸不仅源于肺牵张感受器反馈的丧失，还源于一些未明确的迷走神经传入的丧失。为了探究这种可能性，我们对麻醉的狗的迷走神经进行了冷却。在自主呼吸的狗中，在7摄氏度时赫林-布雷尔反射被消除，但平均呼气时间没有变化，只有在冷却到3摄氏度以下时才延长。在人工通气的狗中，在胸部冷却肺迷走神经并记录膈神经活动。膈神经冲动与呼吸机周期的同步在7摄氏度时停止，呼气暂停缩短；在冷却到3摄氏度以下时又延长。在切断肺迷走神经后，颈迷走神经切断术并未改变呼吸模式。冷却过程中传入冲动的记录表明，在5摄氏度或更低温度时，肺迷走神经传入主要局限于无髓纤维；在3摄氏度时，肺C纤维的背景活动仍为对照的78%，而有髓传入纤维几乎没有活动。我们认为，在平静呼吸时，肺传入C纤维的低频背景活动缩短了呼气时间。
