Chemical Stimulation of Rapidly Adapting Receptors in the Airways
The lungs are known to contain and release a number of biologically active substances that produce important effects both within and outside the lungs themselves. Among the substances are histamine, which is released from mast cells in the lungs (and elsewhere) as a consequence of IgE-mediated antigen-antibody reactions1, and the prostaglandins, in particular PGF2α , which can be released by a number of factors including anaphylaxis, hyperventilation and mechanical stimulation of the lungs . Among the effects produced by these substances are tachypnea and bronchoconstriction, which in dogs are known to have reflex components mediated by afferent fibers in the vagus nerves3–5. The receptors responsible for these reflex effects in the lungs are not known, although they are believed to be receptors other than the slowly adapting stretch receptors, which reflexly are believed to cause apnea and relaxation of airway smooth muscle .One candidate receptor for this role in reflex bronchoconstriction could be the rapidly adapting vagal receptor that we characterized recently in intrapulmonary airways of dogs. These receptors give rapidly adapting responses to maintained hyperinflation of the lungs, and their discharge can be made to increase by several other ventilatory stimuli.
KeywordsAirway Smooth Muscle Smooth Muscle Contraction Lung Mechanic Chemical Stimulation Receptor Response
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