Nasal mucosal permeability after methacholine, substance P, and capsaicin challenge in the rat.

Nasal permeability was studied in anaesthetized rats after topical challenge with methacholine (MC), substance P (SP), or capsaicin. The drugs were applied onto strips of filter paper. After drying, they were inserted into one side of the nasal cavity while the other side received strips without drugs. The filter paper strips were used not only to stimulate secretion but also to collect the resulting fluid. FITC-albumin was given i.v. and the amount appearing in the nasal fluid was captured on the strips and measured by fluorometry. The presence of FITC-albumin in nasal secretions reflects a leakage of plasma through the capillary endothelium and the nasal epithelium. MC, SP, and capsaicin stimulated the secretion of nasal fluid. SP and capsaicin, but not MC increased the concentration of FITC-albumin in the nasal fluid.