We examined the response of tracheal mucosal blood flow normalized for systemic arterial pressure (Q̇trn), water content (VH2O) and luminal dead spac anesthetized sheep. Nebulized histamine produced rapid increases in mean Q̇trn ( + 84%) and VH2O (+ 85%), and a decrease in mean Vtr(-17%)(P<0.05) within 5 min post completion of challenge. Mean Vtr rapidly returned to baseline, while mean Q ̇trn and VH2O remained elevated for 60 and 90 min after challenge, respectively. Pretreatment with chlorpheniramine (H1-antagonist) blocked the changes in Vtr and VH2O, and attenuated the increase in Q̇trn. Metiamide (H2-antagonist) pretreatment abolished the increase in Q̇trn and blunted the increase in VH2O, but had no effect on the decrease in Vtr. 2-methylhistamine (H1-agonist) decreased mean Q̇trn and Vtr (P<0.05) and dimaprit (H2-agonist) increased mean Q̇trn (P<0.05) without changing Vtr. Neither 2-methylhistamine nor dimapritsignificantly altered VH2O Atropine blocked histamine induced decreases in Vtr and slightly attenuatedthe increases in Q̇trn and VH2O. Thus, histamine increased airway smooth muscle tone and mucosal water content principally via H1 receptors, and mucosal perfusion via H2 receptors. The airway smooth muscle contraction involved muscarinic pathways.
- Histamine, and airway smooth muscle, and airway water content, and trachealmucosal
- Trachea, mucosal perfusion
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine