Journal of Applied Physiology, Vol 66, Issue 5 2145-2149, Copyright © 1989 by American Physiological Society
Cholinergic component of histamine-induced bronchoconstriction in newborn guinea pigs
C. Clerici, A. Harf, C. Gaultier and F. Roudot
Departement de Physiologie, Faculte de Medecine, Creteil, France.
The magnitude of parasympathetic reflex-mediated bronchoconstriction during
histamine infusion was compared in anesthetized paralyzed newborn and adult
guinea pigs. The animals were ventilated using a constant-flow ventilator,
and the conductance and compliance of the respiratory system were
continuously monitored. We found that reactivity to histamine infusion was
less in newborns than in adults, because newborns required a larger dose of
histamine than adults (300 vs. 125 ng.kg-1.s-1) to produce an equivalent
decrease in conductance (42 +/- 13 vs. 42 +/- 15%). Vagal interruption by
bilateral cervical vagotomy or muscarinic blockade with atropine (3 mg/kg)
significantly reduced the bronchoconstrictor response to histamine in
adults. By contrast, neither vagotomy nor atropine significantly changed
this response in the newborns. These results indicate the lack of a vagal
component in the bronchoconstriction that histamine induced in the
newborns. Their relative unresponsiveness to histamine might partly be
related to the fact that, in the newborn, histamine mainly acts directly
via its airway receptors.
