Meranzin Hydrate Induces Similar Effect to Fructus Aurantii on Intestinal Motility through Activation of H-1 Histamine Receptors

This experiment studied the potential effect of meranzin hydrate (MH) and decoction of herb Fructus Aurantii (FA) on rat gut motility. It also investigated the prokinetic mechanism of MH. Experiments were performed on male Sprague-Dawley rats (200-220 g). The study included: (1) qualitation of MH and four other known compounds in FA and jejunum after oral administration of FA decoction to rats; (2) in vitro experiment of MH on rat jejunum contractions; (3) in vivo experiment of FA and MH in rats. Dose-dependently, MH (1-100 A mu M) increased amplitude in longitudinal and circular jejunum muscles. Pretreatment of jejunum longitudinal strips with benzhydramine (1 A mu M) remarkably inhibited the contractions induced by histamine (1 A mu M) and MH (10 or 30 A mu M). Pretreatment of jejunum longitudinal strips with atropine (1 A mu M) reduced the contractions induced by acetylcholine (1 A mu M) but did not influence the contractions induced by MH (10 or 30 A mu M). Interestingly, the antagonism of benzhydramine to MH was also verified in vivo. MH can be absorbed into the jejunum following oral administration of FA decoction. In healthy rats, MH (7, 14, and 28 mg/kg) and FA (3.3, 10, and 20 g/kg) both promoted intestinal transit and gastric emptying in a dose-dependent manner when gavaged acutely. In cisplatin model rats, MH (14 and 28 mg/kg) significantly reversed cisplatin-induced delay in gastric emptying. Meranzin hydrate can induce similar effect to Fructus Aurantii on intestinal motility and it was, at least in part, mediated by stimulation of H1 histamine receptors.