Effects of KW-5338 (domperidone) on gastric motility

Distribution of urocortin in the rat's gastrointestinal tract and its colocalization with tyrosine hydroxylase

Urocortin (Ucn), a newly identified member of the corticotropin-releasing factor (CRF) family, is not only expressed in the brain, but also abundantly present in the peripheral tissues, especially in the gastrointestinal tract (GI) as determined by radioimmuoassay. In order to determine the precise localization of urocorin in the GI, we mapped the distribution of urocortin-like immunoreactivity (ir) in the GI of the rat using an immunofluorescence histochemical technique. Ucn, both in the brain and the peripheral tissues, is involved in the regulatory control of host-defense mechanism during stress. In order to study the possible involvement of the sympathetic system in the expression of GI urocortin in response to stress, we examined the effect of chemical sympathectomy on urocortin-ir and its colocalization with tyrosine hydroxylase (TH). UCn was expressed in all parietal cells of the stomach, myenteric and submucosal plexuses as well as in cells in Lieberkühn crypts of the small and large intestine. Most of the acid secreting parietal cells contained both Ucn and TH. Chemical sympathectomy did not affect Ucn immunoreactivity of parietal cells.

The effect of dopamine on rat gastric motility

The inhibitory mechanism of dopamine (DA) on rat gastric motility was investigated in association with DA receptors. Gastric movement was assessed according to the method of Jacoby et al and was expressed with the system of Ludwick et al. (1968). DA inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. Domperidone, a specific antagonist of DA2 receptor, suppressed DA-induced inhibition of gastric movement in a dose-dependent manner. SCH23390, a specific antagonist of DA1 receptor did not affect DA-induced inhibition of gastric movement. LY171555, a specific agonist of DA2 receptor, inhibited gastric movement in both the corpus and antrum in a dose-dependent manner. SKF38393, a specific agonist of DA1 receptor, did not affect gastric movement. These results indicate that DA plays an important role in the inhibitory regulation of gastric motility, through DA2 receptor but not DA1 receptor.

A comparative study on the effects of domperidone, metoclopramide, clebopride and trimebutine on the gastro-duodenal preparation of the guinea pig

Domperidone (dopamine antagonist), metoclopramide and clebopride (both dopamine antagonists and stimulators of the intramural cholinergic system), and trimebutine (spasmolytic) are used in the treatment of digestive disorders such as dyspepsia or gastritis. Our aim was to compare the effects of these compounds on the isolated intact gastroduodenal preparation of the guinea pig. Domperidone (IC50 = 10(-6) M), clebopride (10(-5) M) and metoclopramide (2 X 10(-5) M) antagonized gastric relaxations induced by dopamine. In contrast with clebopride, domperidone and metoclopramide enhanced the amplitude of gastric contractions, moderately reduced contractile frequency, and enhanced antroduodenal coordination in a dose-dependent manner (EC50 for domperidone 3 X 10(-7) M, for metoclopramide 2 X 10(-5) M). Trimebutine reduced gastric spontaneous activity and antroduodenal coordination. Trimebutine had a direct relaxatory effect on gastric tone (EC50 = 4 X 10(-6) M). The mechanism of this inhibitory effect remains unknown but our data indicate that it is not mediated via dopamine or opiate receptor subtypes.

CONCLUSION

domperidone, clebopride, metoclopramide and trimebutine exert distinct and diverse effects on the motility parameters of the gastroduodenal preparation of the guinea pig. These diverging actions may help explain the differences in patients' responsiveness to the treatment of digestive disorders such as dyspepsia or gastritis.