Antiulcer activity of the calcium antagonist propyl-methylenedioxyindene--II. Effects on acid secretion and gastric emptying in rats

Inhibitory Effects of Hot Water Extract of the Stevia Stem on the Contractile Response of the Smooth Muscle of the Guinea Pig Ileum

The effects of a hot water extract of the stem of Stevia rebaudiana on the smooth muscle of isolated guinea pig ileum were investigated. The butyl alcohol layer of the extract antagonized the contractions of the isolated guinea pig ileum induced by histamine (1 x 10(-5) M) and acetylcholine (1 x 10(-5) M) in a concentration-dependent manner. The butyl alcohol layer of the extract also showed inhibition of CaCl(2) (1 x 10(-3)-3.8 x 10(-1) M)-induced contractions. The antagonism of the extract was considered to be non-specific, but this action might be related to an influx of extracellular Ca(2+). With column chromatography preparation, the active component was assumed to be as stevioside. The antagonistic effects exerted by the stem extract of Stevia rebaudiana contributed to the gastroprotective activity of the extract in animals fed dietary histamine.

Glucagon-like peptide-1 inhibits gastric emptying via vagal afferent-mediated central mechanisms

Exogenous administration of glucagon-like peptide-1-(7-36) amide (GLP-1), an insulinotropic hormone, inhibits gastric emptying and acid secretion in humans. The role of GLP-1 as a regulator of gastric function is elusive. In gastric fistula rats, vagal afferent denervation and peripheral administration of the GLP-1 receptor antagonist exendin-(9-39) amide enhanced emptying of a glucose meal, whereas intracerebroventricular exendin was ineffective. The rate of saline emptying was attenuated by peripheral as well as by central administration of GLP-1, and pretreatment with exendin by the respective routes reversed the inhibition by GLP-1. Vagal afferent denervation abolished the central and peripheral action of GLP-1 on gastric emptying. Neither peripheral cholinergic nor adrenergic blockade altered the delay of methyl cellulose meal emptying by intracisternal GLP-1 injection. Acid secretion in conscious pylorus-ligated rats was inhibited by intracisternal GLP-1 administration, whereas systemic GLP-1 was ineffective. These results support the notion that GLP-1 receptors participate in the central and peripheral regulation of gastric function. Furthermore, vagal afferent nerves mediate the inhibitory action of GLP-1 on gastric motor function. GLP-1 may be a candidate brain-gut peptide that acts as a physiological modulator of gastric function.

Antiulcer activity of the calcium antagonist propyl-methylenedioxyindene--V. Localization of site of action

1. Propyl-methylenedioxyindene (pr-MDI) is an intracellular calcium antagonist which inhibits cold-restraint stress ulceration at subcardiovascular doses (less than or equal to 30 mg/kg). It also inhibits gastric acid secretion evoked by RX77368 (a stable analog of thyrotropin-releasing hormone, the putative mediator of cold-restraint stress ulcers). 2. The objective of this investigation was to localize the site of the inhibitory effect of pr-MDI on gastric acid secretion stimulated by intracisternal (i.c.) administration of RX77368 (100 ng) in rats. 3. Peripheral administration of pr-MDI (30 mg/kg i.p. or i.v.) inhibited the elevated basal and the RX 77368-induced acid secretion in conscious 2-hr pylorus-ligated rats. This effect was completely blocked in anesthetized (urethane or pentobarbital) acute gastric fistula rats. 4. Intracisternal administration of pr-MDI (0.1-1 mumol) produced a dose-related inhibition of acid secretion in conscious pylorus-ligated rats. However, urethane anesthesia completely blocked the inhibitory effect of i.c.-administered pr-MDI (1 mumol) on RX77368-induced acid secretion. 5. Since previous studies indicate that anesthesia does not inhibit peripheral actions of pr-MDI (e.g. the antiarrhythmic effect), the convergent evidence suggests that the inhibitory effect of pr-MDI on gastric acid secretion is mediated primarily via the central nervous system.

Adrenalectomy, but not vagotomy, reverses the worsening effect of Ca2+ blockers on ethanol-induced gastric lesions in rats

This study examines the influence of the adrenals and of the vagus nerve on the lesion-worsening action of nitrendipine or verapamil on 75% ethanol-induced gastric mucosal damage in rats. Bilateral adrenalectomy antagonized ethanol lesion aggravation by nitrendipine or verapamil; instead, dose-related lesion reduction was seen. Dexamethasone treatment of adrenalectomized rats restored the lesion-enhancing effects of both Ca2+ channel blockers. Bilateral subdiaphragmatic vagotomy failed to abolish the adverse action of nitrendipine or verapamil on ethanol lesions. The findings suggest that the adrenal corticoids modulate the worsening effect of Ca2+ channel antagonists on ethanol-induced gastric damage; when the influence of the adrenal steroids is removed, these compounds become gastroprotective.

Antiulcer activity of the calcium antagonist propyl-methylenedioxyindene. IV. Effects on gastric lesions in rats induced by cold-restraint stress and thyrotropin-releasing hormone

Propyl-methylenedioxyindene (pr-MDI; 30 mg/kg, i.p.), an intracellular calcium antagonist, significantly reduced the number and size of erosions per stomach induced by cold-restraint stress by 69% and 86%, respectively. Our previous findings indicate that the antiulcer activity of pr-MDI is highly correlated with its inhibitory effect on gastric motor activity. Since central TRH is suggested as the brain mediator responsible for cold-restraint stress gastric ulcers in rats, the inhibitory action of pr-MDI was evaluated in the TRH-induced gastric lesion model. Pr-MDI (30 mg/kg) did not reduce the gastric erosions induced by intracisternal administration of 100ng RX77368, a stable thyrotropin-releasing hormone (TRH) analogue, even though it abolished the RX77368-induced stimulation of gastric emptying, gastric acidity, and acid output. Since pr-MDI (30 mg/kg, i.p.) significantly inhibited the stimulation of gastric motility by both cold-restraint stress and TRH, but only cold-restraint stress-induced gastric erosions were effectively reduced by the drug, the present findings suggest a possible dissociation between the ulcerogenic mechanisms of cold-restraint stress and intracisternal administration of TRH.