Re. Santing et al., CONTRIBUTION OF A CHOLINERGIC REFLEX MECHANISM TO ALLERGEN-INDUCED BRONCHIAL HYPERREACTIVITY IN PERMANENTLY INSTRUMENTED, UNRESTRAINED GUINEA-PIGS, British Journal of Pharmacology, 114(2), 1995, pp. 414-418
1 In conscious, permanently instrumented, unrestrained, ovalbumin-sens
itized guinea-pigs the development of allergen-induced bronchial hyper
reactivity to histamine- and methacholine-inhalation was investigated
after the early as well as after the late asthmatic response. 2 The al
lergen-induced increase in bronchial reactivity to histamine was signi
ficantly higher than to methacholine. 3 The muscarinic receptor antago
nist, ipratropium bromide (1.0 mM, 3 min inhalation), blocked methacho
line-induced bronchoconstriction and caused a significant 1.7 fold inh
ibition of the histamine-induced bronchoconstriction of control animal
s. 4 A lower dose of ipratropium bromide (0.1 mM, 3 min inhalation) ha
d no significant effect on histamine-induced bronchoconstriction in co
ntrol animals, but significantly reduced the allergen-induced increase
in bronchial reactivity to histamine between the early and late asthm
atic response. At 1.0 mM ipratropium bromide, no further reduction was
observed. 5 These results clearly indicate that an exaggerated cholin
ergic reflex mechanism contributes to allergen-induced bronchial hyper
reactivity to histamine.