Antigen challenge and canine tracheal mucus.

Tracheal mucus hypersecretion was demonstrated in 7 dogs with cutaneous sensitivity to extracts of Ascaris suum when the dogs were exposed to aerosols of the same antigen. There was a correlation between antigen skin sensitivity and the aerosol dose at which hypersecretion first occurred. In addition to hypersecretion, antigen challenge led to significant alterations in mucus viscoelasticity. The dose-response pattern was similar to that seen with methacholine and histamine aerosol administration in dogs employing the same methodology. The antigen-induced hypersecretion was blocked or substantially reduced by pretreatment with atropine, H1-antagonists, and thiazinamium chloride. These observations suggest that mucus hypersecretion associated with A. suum challenge in dogs involves histamine release and proceeds at least in part via a cholinergic mechanism.