Sensory and Inflammatory Peptide Receptors in Airways

This chapter discusses the receptors for substance P (SP), neurokinins, and calcitonin-gene-related peptide and for bradykinin and anaphylatoxins. SP is localized to unmyelinated sensory nerves in airways. SP causes microvascular leakage in airway vessels, as measured by extravasation of Evans blue dye, which binds to plasma albumin. SP-immunoreactive nerves are also seen in airway smooth muscle, around submucosal glands, around submucosal blood vessels, and in relation to parasympathetic ganglia. Calcitonin gene-related peptide receptors are localized in high density to pulmonary and vascular smooth muscle. SP facilitates cholinergic nerve-induced contraction in rabbit trachea without affecting acetylcholine contractile responses, suggesting the presence of facilitatory tachykinin receptors on airway postganglionic cholinergic nerves. Tachykinins produce their effects by interacting with specific surface receptors. Using several tachykinins it is possible to define different patterns of response, suggesting the existence of subtypes of tachykinin receptor.