Neurogenic inflammation in rat trachea is accompanied by increased negativity of interstitial fluid pressure

The present experiments were performed to investigate whether neurogenic inflammation in rat trachea (with edema formation and protein extravasation when the circulation is intact) induced by electrical field stimulation of neuropeptide-containing C fibers in the vagal nerve is accompanied by increased negativity of interstitial fluid pressure (P(if)). Increased negativity of P(if) in the trachea occurs in dextran anaphylaxis and mast cell degranulation and facilitates edema formation under these circumstances. Experiments were performed after circulatory arrest had been induced in pentobarbital anesthesia to prevent edema formation, which will raise P(if) and potentially cause underestimation of an increased negativity of P(if). After induction of circulatory arrest, the vagal nerve was isolated and placed in a stimulating electrode. The trachea was then exposed and covered with mineral oil, and measurement of P(if) was started as soon as possible thereafter. P(if) was measured with sharpened glass capillaries (tip diameter, 3 to 7 microns) connected to a servocontrolled counterpressure system. P(if) in the control group (n = 12) did not change throughout the observation period. Electrical stimulation of the left vagal nerve caused P(if) to fall in all experiments, from -1.1 +/- 1.1 mm Hg in the control condition to an average of -10.6 +/- 3.4 mm Hg (n = 9, P < .01). In some experiments, a continuous recording of P(if) was obtained, showing that the reduction of P(if) started within 30 seconds after onset of stimulation to reach and later remain at a stable level within a few minutes. The experimental protocol was repeated after the C fibers had been nearly depleted of neuropeptides with capsaicin.(ABSTRACT TRUNCATED AT 250 WORDS)