Open Access

We improved our previous model of tracheal tube preparation and examined the effects of oral treatment of rats with carbocisteine (CCS) and its interaction with bronchial epithelium. The model permitted isometric or isotonic measurements of smooth muscle contraction or relaxation in cannulated or tracheal ring preparations, with or without epithelium. We found that oral treatment with carbocisteine and not preincubation of preparations in vitro, diminished sensitivity of preparations without epithelium to carbachol (EC50, -log(M) values: IN -luminary perfusion, -EP, controls vs. CCS: 5.8±0.06 vs. 5.5±0.09, p<0.005; OUT - serosal perfusion, -EP, controls vs. CCS: 5.9±0.06 vs. 5.6±0.05, p<0.005), while the sensitivity to aminophylline, degree of shortening, and the velocity of contraction of rat tracheal rings stimulated by 10-6M carbachol was not affected. Normal sensitivity to carbachol stimulation was re-established if preparations were preincubated with capsaicin. We conclude that carbocisteine has small inhibitory effects on the sensitivity to carbachol of the rat tracheal smooth muscle denuded of epithelium. Described model is valuable for examining the effects of bronchial epithelium on bronchial smooth muscle contraction.