title: Attenuation of pulmonary afferent input by vagal cooling in dogs.
abstract: 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.
authors: Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
authors: A
authors: A
authors: Jonzon
authors: T E
authors: TE
authors: Pisarri
authors: A M
authors: AM
authors: Roberts
authors: J C
authors: JC
authors: Coleridge
authors: H M
authors: HM
authors: Coleridge
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D003080:Cold Temperature; D004285:Dogs; D008168:Lung / Q000294:innervation*; D008465:Mechanoreceptors / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D011661:Pulmonary Stretch Receptors / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*