Effect of epithelium removal on 5-HT-induced contraction. Fresh (A), 4 days of organ culture in the absence (B) and presence (C) of IL-1β (10 ng/ml). Epithelium was removed after the trachea had been organ cultured in the absence and presence of IL-1β. The results were compared with data obtained in segments with an intact epithelium. Each data point is derived from 5–10 experiments and represented as the mean ± S.E.M. Statistical analysis was performed with two-way ANOVA with Bonferroni post-test to compare the two corresponding data points at each concentration, no significant differences were seen (P > 0.05).