Reflex control of the tracheal vasculature of sheep

1993.-Arteries to the cervical trachea were perfused at con-stant flow in anesthetized sheep. Perfusion pressures (PP), blood pressure (BP), and changes in tracheal smooth muscle tone (Ptr) were measured. Stimulation of pulmonary C-fiber receptors decreased PP (-6.5%) and BP (-16.8%) and in-creased Ptr (+61.5%), changes prevented by vagotomy and therefore reflex. Stimulation of cardiac receptors and slowly adapting pulmonary stretch receptors decreased PP (-7.9%) and BP (-21.0) and increased Ptr (+19.0%), changes reversed by vagotomy and therefore reflex. Stimulation and inhibition of slowly adapting pulmonary stretch receptors had no vagal-dependent effect on PP and BP, but inflation decreased (-20.3%) and deflation increased Ptr (+35.2%), effects abol-ished by vagotomy and therefore reflex. Systemic hypoxia in-creased PP and BP before and after vagotomy (+12.2 an