Singulair (Montelukast) is a potent and selective leukotriene D4 receptor antagonist, often used in treating inflammatory conditions of the respiratory system such as allergic rhinitis and asthma. However, the eVects of singulair given intratracheally have rarely been well explored. To verify the eVect of singulair, which acts on the tracheal smooth muscle directly in vitro. We used our preparation to test the eVects of singulair on isolated rat's tracheal smooth muscle. The following assessments of singulair were performed: (1) effect on the tracheal smooth muscle resting tension, (2) eVect on contraction caused by 10-6 M methacholine as a parasympathetic mimetic, and (3) eVect of the drugs on electrically induced tracheal smooth muscle contractions. The results indicated that the addition of methacholine to the incubation medium caused the trachea to contract in a dose-dependent manner. Addition of singulair at doses of 10-5 M or above elicited a signiWcant relaxation response to 10-6 M methacholine-induced contraction Singulair could not inhibit electrical Weld stimulationinduced spike contraction. It also had a minimal eVect on the basal tension of trachea as the concentration increased. This study showed that the high concentrations of singulair also had an anti-cholinergic eVect for relieving symptoms of asthma.
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