Action of nicotine on guinea-pig isolated bronchial smooth muscle preparation

In the isolated bronchial preparation of the guinea-pig, nicotine induced a contraction but not a relaxation. The contractile response of the bronchial preparation to nicotine was inhibited by hexamethonium and d-tubocurarine but not influenced by atropine and tetrodotoxin. In the isolated tracheal preparation of the guinea-pig where nicotine stimulated nicotinic receptor in nervous tissues, the contractile response to nicotine as considerably accelerated by the treatment of the guinea-pig with egg-albumin, while the contractile response of the bronchial preparation to nicotine was not influenced by the same treatment. These results suggest that a possible site of action of nicotine in the isolated bronchial preparation is not on the nervous cells but on the smooth muscle cells. However, we could not rule out a contribution by chemical mediators released by nicotine in the contractile mechanisms in the bronchial preparation.