Protection against necrotizing agents-induced gastric lesions in rats. Unrelated to inhibition of gastric motility

Characterisation of alpha2-adrenoceptor subtypes involved in gastric emptying, gastric motility and gastric mucosal defence

The effect of clonidine on ethanol-induced gastric mucosal damage, gastric emptying and gastric motility was compared. The clonidine-induced gastroprotective effect (0.03-0.09 micromol/kg, s.c.) was antagonised by yohimbine (5 micromol/kg, s.c.), prazosin (0.23 micromol/kg; alpha2B-adrenoceptor antagonist) and naloxone (1.3 micromol/kg, s.c.). Clonidine also inhibited the gastric emptying of liquid meal (0.75-3.75 micromol/kg, s.c.) and gastric motor activity (0.75 micromol/kg, i.v.) stimulated by 2-deoxy-D-glucose (300 mg/kg, i.v.). Inhibition of gastric emptying and motility was reversed by yohimbine (5 and 10 micromol/kg, s.c., respectively), but not by prazosin (0.23 micromol/kg, s.c.) or naloxone (1.3 micromol/kg, s.c.). Oxymetazoline-an alpha2A-adrenoceptor agonist-inhibited both gastric emptying (0.67-6.8 micromol/kg, s.c.) and motility (0.185-3.4 micromol/kg, i.v.), whereas it failed to affect gastric mucosal lesions. The results indicate that in contrast to the gastroprotective effect, which is mediated by alpha2B-adrenoceptor subtype, alpha2A-adrenoceptor subtype may be responsible for inhibition of gastric emptying and motility. However, the site of action (central, peripheral, both) remains to be established.

Potassium channel modulators and indomethacin-induced gastric ulceration in rats

BACKGROUND

Different mechanisms have been proposed for the pathophysiology of indomethacin-induced gastric ulceration (IIGU), including changes in gastric mucosal blood flow, motility, and acidity. It seems probable that adenosine 5'-triphosphate (ATP)-dependent potassium channels (K(ATP)) have a regulatory effect on the above factors. The aim of the present study was to investigate the effects of K(ATP) channel modulators, diazoxide as a channel opener and glibenclamide as a K(ATP) antagonist, on IIGU.

METHODS

Male rats were starved for 24 h. Groups of 10 animals were used. Diazoxide at doses of 5, 15, and 45 mg/kg and glibenclamide at doses of 2, 6, and 18 mg/kg were injected intraperitoneally 30 min before the subcutaneous injection of 30 mg/kg of indomethacin. To assess the effects of indomethacin on the gastric mucosal vascular bed, different doses of enalapril and hydralazine, two vasodilators with mechanisms of action independent of K(ATP), were also studied. Gastric mucosal ulceration was noted, and fasting blood sugar was assayed. The data were compared between the groups.

RESULTS

Indomethacin produced gastric ulceration in 100% of rats with a severity rating of 2.15/10. This was prevented by diazoxide and aggravated by glibenclamide. Diazoxide increased and glibenclamide decreased fasting blood sugar. Neither enalapril nor hydralazine showed any effect on IIGU and/or fasting blood sugar.

CONCLUSION

K(ATP) modulators may play an important role in the pathophysiology of IIGU through a peripheral action on mucosal and submucosal blood flow of the stomach, gastric motility, acidity, or an action on the vagus complex center of the brain.

Double-blind, placebo-controlled study on effects of diclofenac sodium and indomethacin on postprandial gastric motility in man

Data from animal studies suggest that NSAIDs-induced gastric damage may be due to increased gastric motility. Such a mechanism, however, has never been tested or demonstrated in man. We evaluated the effects of two frequently prescribed NSAIDs, indomethacin and diclofenac sodium, on postprandial gastric motor activity (a physiologically reproducible stimulus) in healthy volunteers to see whether these compounds increase gastric motility. Twenty-four healthy volunteers of both sexes, 21-35 years of age, underwent a basal gastric motility recording. Thereafter, they were randomized in three groups to receive either placebo, indomethacin (50 mg three times a day) or diclofenac sodium (50 mg three times a day) for a week. At the end of the week, they underwent an identical manometric study. Analysis of the motility tracings showed no difference in gastric antral motility index and in amplitude of gastric antral contractions after NSAIDs with respect to the basal study and to the placebo group. About 50% of subjects (two in the placebo group) complained of side effects. These were transient and mild, except in two subjects taking indomethacin, in whom endoscopy was necessary; one of these had a small prepyloric ulcer. It is concluded that in man NSAID-related gastric damage is unlikely to be due to increased gastric motility.