Original Articles

Effect of ephedrine on myenteric plexus-longitudinal muscle of guinea pig ileum in vitro

Huai-De Shu, Guo-Ping Huang, Zao-Chen Yang


Ephedrine (0.1-1.6 mmol/L) inhibited the twitch response of the myenteric plexus-longitudinal muscle strip of isolated guinea pig ileum to field stimulation in a concentration-dependent manner. The inhibitory action of ephedrine was slightly antagonized by yohimbine (lμmol/L), but not by prazosin (lμmol/L) and propranolol (1μmol/L). The fact that pretreatment of guinea pig with reserpine reduced the inhibitory effect of ephedrine indicated that the action of ephedrine was involved indirectly in released catecholamine. Ephedrine also inhibited the contraction induced by acetylcholine or 5-HT and the spontaneous contraction of longitudinal muscle. The inhibitory action of ephedrine on spontaneous contraction of intestinal smooth muscle was blocked by propranolol. In preparations pretreated with tetrodotoxin, ephedrine triggered a characteristic contractile response. It is suggested that ephedrine has both inhibitory and excitatory action on the ileal longitudinal muscle of guinea pig. In addition, ephedrine has an agonistic action on the presynapticα2 adrenoceptor of cholinergic nerve-intestinal smooth muscle junction.

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