The effect of cholinergic agents on a canine model of allergic asthma

Pharmacologic agents capable of influencing the activity of the cholinergic nervous system were evaluated for possible effects on a canine model of allergic asthma. Dogs with an active cutaneous sensitivity to an antigen (Ag) prepared from Ascaris suum were subjected to repeated aerosol Ag provocations at 2-wk intervals. Ag-induced increases in pulmonary resistance (Rp) and decreases in dynamic lung compliance (Cdyn) were obtained in the presence and absence of drugs. The intravenous administration of atropine or chlorisondamine before, or atropine after, Ag-provocation, in most cases did not result in a significant reduction in Rp increases; however, in some animals an attenuation of the Rp increase was apparent. Aerosol administration of atropine or physostigmine prior to Ag provocation was without effect on Rp increases. None of the agents studied appeared to effect Ag-induced decrease in Cdyn. Similarly, intravenous atropine produced a slight antagonism of exogenous histamine-induced increases in Rp and decreases in Cdyn. These results suggest that the cholinergic nervous system is neither a prominent nor a consistent factor in Ag-induced increases in Rp in dogs.