Jonzon A, Pisarri T E, Roberts A M, Coleridge J C, Coleridge H M
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Respir Physiol. 1988 Apr;72(1):19-33. doi: 10.1016/0034-5687(88)90076-x.
In open chest, artificially ventilated, anesthetized dogs, we examined the effect of vagal cooling on the pulmonary afferent input evoked by hyperinflating the lungs to 3 VT, recording the activity of slowly adapting pulmonary stretch receptors (PSRs), rapidly adapting receptors (RARs) and pulmonary C fibers rostral to the cooling platform. At 15 degrees C and below, input in all three types of fiber was significantly reduced, attenuation being least marked in C fibers. Between 12 degrees C and 7 degrees C, attenuation of RAR input was significantly less than that of PSRs. At 7 degrees C, virtually none of the hyperinflation-evoked increase in PSR activity and only 10% of that in RARs passed the cooling platform--indeed RAR input was less than during normal ventilation at 37 degrees C; by contrast, 40% of the hyperinflation-evoked increase in C fiber activity was still transmitted. Cooling had similar effects on C fiber input evoked by capsaicin. If reflexes are attenuated in proportion to the attenuation of afferent input, our results suggest that a hyperinflation-evoked reflex that survives vagal cooling below 6 degrees C is almost certainly triggered by C fibers.
在开胸、人工通气、麻醉的犬类中，我们通过将肺充气至3倍潮气量（VT）来诱发肺传入输入，研究迷走神经冷却对其的影响，记录冷却平台上方缓慢适应肺牵张感受器（PSR）、快速适应感受器（RAR）和肺C纤维的活动。在15℃及以下时，所有三种纤维类型的输入均显著降低，C纤维的衰减最为不明显。在12℃至7℃之间，RAR输入的衰减明显小于PSR。在7℃时，几乎没有由肺过度充气诱发的PSR活动增加能通过冷却平台，而RAR的增加只有10%能通过——实际上，RAR输入低于37℃正常通气时；相比之下，由肺过度充气诱发的C纤维活动增加仍有40%能被传导。冷却对辣椒素诱发的C纤维输入也有类似影响。如果反射与传入输入的衰减成比例减弱，我们的结果表明，在迷走神经冷却至6℃以下时仍存在的由肺过度充气诱发的反射几乎肯定是由C纤维触发的。
