CHARACTERIZATION OF THE NEUROGENIC PLASMA EXTRAVASATION IN THE AIRWAYS

Release of neuropeptides from sensory nerves causes an increase in vas cular permeability, plasma extravasation and edema. The sensory nerves in the airways can be activated by electrical stimulation of the vagu s nerve or by application of chemical and mechanical irritants, such a s capsaicin, hypertonic saline, isocapnic hyperpnea and cigarette smok e. In rodent airways, the neurogenic plasma extravasation is mediated by tachykinins released from the capsaicin-afferent nerve fibres, and involves activation of neurokinin-l tachykinin receptors. In periphera l guinea-pig airways, neurokinin-2 tachykinin receptors have also been implicated in the neurogenic plasma exudation. The tachykinins can in crease vascular permeability by both a direct effect on venular endoth elium, and indirect mechanisms involving mast cell activation and sero tonin release. Tachykinins and their receptors are present in the huma n airways. Release of tachykinins, following antigen. challenge, has b een demonstrated in the nose and lower airways. In humans, tachykinins have been shown to increase plasma exudation in the nasal mucosa, but whether neurogenic inflammation also occurs in the lower airways stil l remains to be proven.