Contribution of vagal afferents to the volume-timing response to expiratory loads in neonatal lambs.
Expiratory loads elicit volume-dependent reflex increases in expiratory duration (TE) in adult animals. This reflex is mediated by pulmonary vagal afferents. It was hypothesized that this same reflex in newborn lambs is mediated by vagal afferents. Single-breath graded expiratory loads were presented to 4 day old, anesthetized neonatal lambs through a facemask (FM), via tracheostomy (TR) and after the cervical vagi were severed bilaterally in the TR animals (VAG). In FM and TR studies, expired volume (VE) decreased and TE increased with increasing load magnitude. There was no significant difference in the VE-TE curves for FM and TR. These results demonstrate that pulmonary vagal afferents are mediating the volume-related reflex modulation of TE during expiratory loading in the anesthetized neonatal lamb which is unaffected by bypass (TR) of upper airway afferents.
Webb
B
B
Department of Physiological Sciences, University of Florida, Gainesville 32610, USA.
Hutchison
A A
AA
Davenport
P W
PW
D000818:Animals; D012123:Pulmonary Ventilation / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012119:Respiration / Q000502:physiology*; D012756:Sheep; D014630:Vagus Nerve / Q000502:physiology*