Abstract
The effect of substance P (SP) and methacholine (MC) on nasal fluid secretion was studied in anesthetized rats. Pre-weighed filter papers impregnated with the challenging agent were applied to the nasal mucosa, changed every 5 minutes and reweighed to measure the secretion absorbed. SP evoked a dose-dependent increase in nasal secretion that was not affected by pretreatment with propranolol, hexamethonium, lidocaine, or chlorpheniramine combined with ranitidine but was inhibited by the SP antagonist (d-Pro2, d-Trp7,9)-SP. MC evoked a dose-dependent increase in nasal secretion that was inhibited by atropine but not by (d-Pro2, d-Trp7,9)-SP. The secretory response to SP was greater than that to MC at equimolar doses.
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