Substance P-induced increase in vascular permeability in the rat trachea does not depend on neutrophils or other components of circulating blood.

An intravascular injection of substance P is known to increase vascular permeability in the rat trachea. Electrical stimulation of the cervical vagus nerve produces a similar response, presumably by releasing substance P or other tachykinins from sensory nerve endings. In the present study, we sought to determine whether the increase in vascular permeability induced by intravascular substance P or by vagal stimulation requires the presence of neutrophils or other components of circulating blood. To eliminate circulating blood, we perfused into the aorta of anesthetized rats an oxygenated Krebs-Henseleit solution containing albumin and monastral blue, a colloidal pigment that does not cross normal tracheal blood vessels. We then injected substance P intravascularly or electrically stimulated the right cervical vagus nerve. Increases in vascular permeability were quantified by using a microspectophotometer to measure the amount of extravasated monastral blue in tracheal whole-mounts. We found that the elimination of neutrophils and other components of circulating blood did not prevent the increase in tracheal vascular permeability induced by intravascular substance P or by vagal stimulation.