Chlorpheniramine對離體大白鼠氣管平滑肌的效應

BACKGROUND: Chlotrimeton (CTM) is a classical antihistamine. It is often used as a classical histamine receptor-l (H1) antagonist in rhinitis patients who are suffering from sneezing and rhinorrhea. The effect of H1 antagonist on nasal mucosa in vivo is well known; however, the effect of the drug on tracheal smooth muscle has been rarely explored. The aims of this paper were to study the effects of CTM on isolated rat's tracheal smooth muscle.
MATERIALS AND METHODS: We used our preparation to test the effectiveness of CTM on isolated rat's tracheal smooth muscle. The following assessments of CTM were performed: (1) effect on tracheal smooth muscle resting tension; (2) effect on contraction caused by 10^(-6) M methacholine as a parasympathetic mimetic; (3) effect of the drug on electrically induced tracheal smooth muscle contractions.
RESULTS: Results indicated that addition of a parasympathetic mimetic to the incubation medium caused the trachea to contract in a dose-dependent manner. CTM had a minimal effect on the basal tension of trachea as the concentration increased. Addition of CTM at doses of 10^(-6) M or above elicited a relaxation response to 10^(-6) M methacholine-induced contraction. CTM could also inhibit electrical field stimulation (EFS) induced spike contraction.
CONCLUSION: This study indicated that high concentrations of CTM might actually antagonize the methacholine-induced contraction and could relief the symptoms of asthma. At the same concentrations of CTM, it might inhibit parasympathetic function of the trachea.