Reflex bronchial vasodilation in dogs evoked by injection of a small volume of water into a bronchus.
Injection of water into a lobar bronchus stimulates airway C-fibers and rapidly adapting receptors and evokes airway defense reflexes. To determine whether this stimulus also evokes a reflex increase in bronchial blood flow (Qbr), we injected 1-2 ml of water into a lobar bronchus in anesthetized dogs. Injection decreased arterial pressure but increased Qbr from 9 +/- 1 to 21 +/- 3 ml/min. The increase had a latency of 6-8 s and reached a peak after approximately 20 s; Qbr returned to control after 60-90 s. Airway mucosal blood flow, measured by colored microspheres, increased in proportion to Qbr. In contrast, flow in an adjacent intercostal artery that did not supply the airway decreased slightly. Injection of isosmotic saline had little effect. In 13 of 16 dogs, the water-induced increase in Qbr was abolished by cutting or cooling the cervical vagus nerves and hence was entirely dependent on centrally mediated vagal pathways. When the vagus nerves were intact, about one-third of the vasodilator response remained after pharmacological blockade of muscarinic and adrenergic receptors. We conclude that in dogs the defense response to water in the lower airways includes a large increase in Qbr that is partly due to activation of nonadrenergic noncholinergic autonomic pathways.
Pisarri
T E
TE
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Coleridge
H M
HM
Coleridge
J C
JC
D000818:Animals; D017776:Autonomic Pathways / Q000502:physiology; D001980:Bronchi / Q000098:blood supply* / Q000187:drug effects; D004285:Dogs; D007267:Injections; D007820:Laryngeal Mucosa / Q000098:blood supply / Q000502:physiology; D007830:Larynx / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D012018:Reflex / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014867:Water
D014867:Water