title: Effect of PAF on parasympathetic contraction of canine airways.
abstract: Platelet-activating factor (PAF) increases the bronchoconstrictor response of mammalian airways to cholinergic agonists and is thus implicated as a potential mediator of airway hyperreactivity. This study further defines the nature of the increase in airway responsiveness induced by PAF. We employed an in situ canine tracheal preparation, which allows differentiation of the effects PAF has on airway smooth muscle contraction from confounding effects it has on inducing airway edema and secretions. We found that PAF, infused regionally into tracheal arteries, increases the responsiveness of the trachealis muscle to parasympathetic stimuli in a dose-dependent manner. This effect occurred within 15 min. To determine whether the increase in trachealis muscle responsiveness resulted from effects localized to the trachea, we compared the effect of PAF on the tracheal segment with effects of the lower airways of the lung. Delivered to the arteries perfusing the tracheal segment, PAF did not increase lung resistance during vagus nerve stimulation. These data indicate that airway hyperresponsiveness elicited by PAF results from regional stimulation and/or release of mediators that augment tracheal contractility and that this effect is distinct from systemic effects elicited by PAF.
authors.affiliation: National Jewish Center for Immunology and Respiratory Medicine, Department of Medicine, University of Colorado Health Sciences Center, Denver 80206.
authors.forename: R A
authors.initials: RA
authors.lastname: Bethel
authors.forename: S P
authors.initials: SP
authors.lastname: Curtis
authors.forename: D C
authors.initials: DC
authors.lastname: Lien
authors.forename: C G
authors.initials: CG
authors.lastname: Irvin
authors.forename: G S
authors.initials: GS
authors.lastname: Worthen
authors.forename: A R
authors.initials: AR
authors.lastname: Leff
authors.forename: P M
authors.initials: PM
authors.lastname: Henson
mesh_terms: D000818:Animals; D004285:Dogs; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects* / Q000294:innervation / Q000502:physiology
chemical_list: D010972:Platelet Activating Factor