Do nasal mast cells release histamine on stimulation with substance P in allergic rhinitis

Summary The effects of nasal administration of increasing doses of exogenous substance P have been studied in patients with allergic rhinitis treated with placebo or with the H1 antagonist certirizine (10 mg twice daily for 3 days). Responses to substance P were assessed by posterior rhinomanometry (measuring nasal airway resistance) and by measure of histamine. protein and albumin production and cell recovery in nasal lavage fluids before and after challenge. Substance P induced a dose-dependent increase in nasal airway resistance which was similar after treatment with either cetirizine or placebo (maximal increase in nasal airway resistance was 4-2-fold greater than the baseline with the placebo and 4-7-fold greater than the baseline with cetirizine). No histamine release was observed. Similar increases in protein and albumin production were observed after stimulation with substance P along with the placebo (protein: from 0.35±0.11 to 3.31±0.62 mg and albumin: from 0.09±0.04 to 2.08±0.39 mg) and when combined with cetirizine treatment (proteins: from 0.42±0.09 to 3.62±0.77 and albumin: from 0.17±0.04 to 2.19±0.51 mg). After stimulation with substance P, percentages of neutrophils recovered in nasal fluids increased from 26.2±11.5 to 54.5±9.5 with the placebo and from 35.5±11.0 to 53.6±9.5 with cetirizine. Eosinophils were inconsistently found after substance P stimulation during both treatments. In conclusion, nasal response lo substance P is not modified by cetirizine which suggests that the effect of substance P is not secondary to histamine release in the nose in man.