Effects of cimetidine and atropine sulfate on gastric secretion and healing of gastric and duodenal ulcers in rats

Influence of aging on gastric ulcer healing activities of the antioxidants alpha-tocopherol and probucol

In the present study, we compared the effects of alpha-tocopherol and probucol, antioxidants, on the healing of acetic acid-induced gastric ulcers in 8-, 48- and 96-week-old rats. The repeated oral administration of alpha-tocopherol (16 mg/kg twice daily) and probucol (1000 mg/kg twice daily) for 14 consecutive days markedly accelerated the gastric ulcer healing in 48- and 96-week-old rats as well as 8-week-old ones. The ulcer healing effects of both drugs were not significantly different among the rats at three different ages. The superoxide dismutase (SOD) activity in the ulcerated region of 8-, 48- and 96-week-old rats was markedly lower than that in the unulcerated region. In contrast, the thiobarbituric acid (TBA)-reactive substance content, an index of lipid peroxidation, in the ulcerated region of rats at three different ages markedly increased, as compared to that in the unulcerated region. The SOD activity tended to decrease with aging, while the TBA-reactive substance content gradually increased. The repeated administration of alpha-tocopherol and probucol accelerated the ulcer healing and inhibited the increase in the TBA-reactive substance content in the ulcerated region. These results suggest that alpha-tocopherol and probucol promote the ulcer healing by their potent antioxidant activities in 48- and 96-week-old rats as well as 8-week-old rats.

Effects of cytochrome P450 (CYP) 3A4 inhibitors on the anxiolytic action of tandospirone in rat contextual conditioned fear

The azapirone derivatives, including tandospirone and buspirone, are anxiolytics with 5-HT(1A) receptor agonistic action. Previous in vitro studies have suggested these azapirone derivatives are mainly metabolized by the cytochrome P450 (CYP) 3A4 isoform. The purpose of this study was to clarify the effects CYP3A4 inhibitors have on the anxiolytic action of tandospirone in a conditioned fear stress rat model. One day after fear conditioning, the orally administered tandospirone (30-100 mg/kg) significantly inhibited conditioned freezing in a dose-dependent manner. Co-administration of oral tandospirone and CYP3A4 inhibitors [ketoconazole (10 mg/kg, i.p.) and cimetidine (200 mg/kg, p.o.)] markedly inhibited conditioned freezing. Ketoconazole significantly increased the anxiolytic effect of buspirone similar to tandospirone. As with freezing behavior, the plasma concentrations of tandospirone and buspirone were increased by CYP3A4 inhibitors. This suggests the CYP3A4 isoform is involved in the metabolism of tandospirone, in vivo. Therefore, drugs with CYP3A4 inhibitory property may facilitate the anxiolytic effect of tandospirone when treating human anxiety disorders.

Influence of aging on gastric ulcer healing activities of cimetidine and omeprazole

In this study, we compared the effects of cimetidine and omeprazole on the healing of acetic acid-induced gastric ulcers in 8-, 48-, and 96-week-old rats. The repeated oral administration of cimetidine or omeprazole for 14 consecutive days markedly accelerated the ulcer healing in 8- and 48-week-old rats. However, both drugs were ineffective in 96-week-old rats. The basal gastric acid secretion of 8-, 48-, and 96-week-old rats decreased with aging. A single oral administration of cimetidine or omeprazole strongly decreased basal gastric acid secretion in the three different ages of rats. Cimetidine and omeprazole produced a potent and sustained serum gastrin-elevating action in 8- and 48-week-old rats. However, the gastrin-elevating actions of both drugs in 96-week-old rats were much weaker than in the 8- and 48-week-old rats. These results indicate that cimetidine and omeprazole have potent gastric ulcer healing actions in 8- and 48-week-old rats, as well as potent serum gastrin-elevating actions, but both drugs are ineffective in 96-week-old rats, which have lost their gastrin-elevating actions.

A comparative study on the activity of lansoprazole, omeprazole and PD-136450 on acidified ethanol- and indomethacin-induced gastric lesions in the rat

1. The proton pump inhibitors lansoprazole (LP) and omeprazole (OP) and the cholecystokinin (CCK)-receptor antagonist PD-136450 (PD) provide a broad spectrum of activities in their ability to inhibit gastric acid secretion and protect the stomach against ulcerogens. In the present study, we investigated the protective effects of these compounds against gastric ulcers induced by acidified ethanol (AE) and indomethacin. 2. Both AE (60% ethanol in 150 mmol/L HCl, 1 mL/rat) and indomethacin (30 mg/kg) produced gastric haemorrhagic lesions in the rat 1 and 6 h after oral administration, respectively. 3. The gastric mucosal protective effects of LP (1-20 mg/kg), OP (0.5-10 mg/kg) and PD (1-20 mg/kg), administered either orally or subcutaneously (s.c.) 30 min before the administration of AE or indomethacin, were dose dependent against both models of ulcer induction. 4. To determine whether the cytoprotective effect of LP, OP and PD (each 10 mg/kg) was mediated by endogenous prostaglandins (PG), indomethacin (10 mg/kg, s.c.) was administered 15 min before AE to inhibit prostanoids biosynthesis. Indomethacin reduced the cytoprotective effects of OP, but not LP, administered either orally or s.c. Indomethacin reduced the cytoprotective effect of PD administered orally, although the effect was much less significant than when PD was administered s.c. The results exclude the role of PG in mediating the protective effects of LP, whereas the possibility exists for PG to have a role in mediating the protective effects of OP and PD. 5. To investigate the possible involvement of endogenous nitric oxide (NO) in the cytoprotective action of LP, OP and PD, we treated rats with a selective inhibitor of NO synthesis, namely NG-nitro-L-arginine methyl ester (L-NAME; 25 mg/kg, s.c.). Administration of L-NAME 15 min prior to LP, OP or PD (each 10 mg/kg) orally or s.c. and challenge with AE or indomethacin did not significantly increase the degree of the ulcer index and L-NAME was not able to antagonize the protective effects of LP, OP and PD, thus excluding the role of NO in mediating the protective effects of these drugs. However, the effects of PD in reducing the indomethacin-induced ulcer index were less significant in the presence than the absence of L-NAME (P < 0.05 vs P < 0.001, respectively), suggesting a role for NO. 6. In conclusion, the results of the present study suggest that LP and OP are equally effective against AE- as well as indomethacin-induced gastric ulcers and were more potent than PD in protecting the stomach against ulcer formation. Lansoprazole, OP and PD bring about their cytoprotective action through the reduction of acid secretion and some other unknown mechanisms. However, OP and PD may exert their cytoprotective action through PG and NO pathways.

Gastroprotective effect of Copaifera langsdorffii oleo-resin on experimental gastric ulcer models in rats

The effects of oleo-resin obtained from the stem bark of Copaifera langsdorffii on ethanol, indomethacin and hypothermic restraint-stress induced gastric lesions were studied in rats. Oral administration of oleo-resin at doses of 200 and 400 mg/kg provided dose-dependent significant protection against gastric damage caused by ethanol and restraint stress, and at a dose of 400 mg/kg it also prevented the gastric ulceration induced by indomethacin. Further, in the 4 h pylorus ligated rats, the accumulation of gastric juice volume and the mucus secretion was significantly enhanced by oleo-resin whereas the total acidity was inhibited. These results highlight the gastroprotective potential of C. langsdorffii oleo-resin and the need for a systematic study on this traditional remedy.

Anti-ulcer activity of higher primary alcohols of beeswax

The anti-ulcer effects of a natural mixture of higher aliphatic primary alcohols, designated D-002, isolated from beeswax, were compared with those of cimetidine on indomethacin-, ethanol-, water-immersion-induced ulcers and on gastric secretion in rats. D-002 (25-50 mg kg-1 p.o.) was similar to cimetidine in dose-dependently reducing the duration of indomethacin-induced ulcers while also being effective in preventing ethanol-induced ulcers, which are not affected by cimetidine. On the other hand, D-002 (100 mg kg-1) moderately decreased the volume of gastric basal secretion in pylorus-ligated rats, but not the acidity. Nevertheless, it inhibited gastric ulcer induced by pylorus-ligation at doses (50 mg kg-1) that were ineffective in decreasing the volume. In addition, 100 mg kg-1 of D-002 prevented the formation of acute gastric ulcers induced in rats by water-immersion stress. The results demonstrate the anti-ulcer activity of the preparation in different experimental models suggesting its potential value for ulcer therapy.

Effect of cimetidine and omeprazole on gastric ulcer healing of rats with limited food intake time

The effects of cimetidine, omeprazole and atropine sulfate on the healing of acetic acid-induced gastric ulcers in rats with limited food intake time (9:00-10:00 a.m. and 5:00-6:00 p.m.) were evaluated 15 days after the acid injection. Oral repeated administration of cimetidine (25-100 mg/kg twice daily) or omeprazole (10-50 mg/kg once daily) dose dependently accelerated ulcer healing. Atropine sulfate (10 mg/kg twice daily, p.o.) was ineffective. A single oral administration of omeprazole (50 mg/kg) or cimetidine (100 mg/kg) resulted in potent and long-lasting anti-acid secretory and gastrin-releasing actions. The degree and duration of anti-acid secretion by atropine sulfate were equal to those of cimetidine, but the elevation of gastrin release by atropine sulfate was weak and temporary. These results indicate that the gastric ulcers of rats with a limited food intake time are useful for evaluating the healing effects of cimetidine and omeprazole on gastric ulcers. In addition, the effects of both drugs may be related to the increased gastrin release rather than to the reduced acid secretion.

Antisecretory and antiulcer effects of ebselen, a seleno-organic compound, in rats

The effects of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-on), a metal-containing organic compound, on gastric secretion and gastric ulceration were examined in rats. Intraduodenal ebselen (30 to 300 mg/kg) significantly and dose-dependently inhibited gastric secretion in pylorus-ligated rats. Both aspirin- and water-immersion restraint stress-induced ulcers were significantly prevented by oral administration of ebselen at doses equivalent to the antisecretory doses. These results indicate that the antisecretory effect of ebselen underlies its antiulcer effect in these models.

Effect of DS-4574, a novel peptidoleukotriene antagonist with mast cell stabilizing action, on acute gastric lesions and gastric secretion in rats

DS-4574 is a peptidoleukotriene antagonist with mast cell stabilizing activity. In the present study, we studied the effects of this compound on gastric secretion and various acute gastric lesions in rats. Intraduodenal administration of DS-4574 at doses of 5 to 10 mg/kg significantly and dose-dependently inhibited gastric acid secretion in pylorus-ligated rats, but a further increase in the dose up to 50 mg/kg did not cause any further inhibition. Shay ulceration in response to pylorus ligation was dose-dependently prevented by DS-4574 (10-25 mg/kg, i.d.). Water-immersion restraint stress- and aspirin-induced gastric ulcers were also significantly prevented in a dose-related manner by oral pretreatment with DS-4574 (10-50 mg/kg). The lower doses of DS-4574 (1-10 mg/kg, p.o.) significantly and dose-dependently protected the gastric mucosa against the necrotizing action of either absolute ethanol or concentrated hydrochloric acid, indicating that this compound possesses a potent gastroprotective activity. These antiulcer and gastric protective effects of DS-4574 were more potent than those of cimetidine used as a reference drug. These findings suggest that DS-4574 is useful for peptic ulcer therapy, as well as for the therapy of various allergic diseases, including asthma.

Developmental levels and androgen responsiveness of hepatic mono-oxygenases of male rats perinatally exposed to maternally administered cimetidine

Cimetidine, a widely prescribed, potent histamine H2-receptor antagonist, is unrelatedly a mild antiandrogen. Since perinatal androgens are essential for normal masculine imprinting, we wanted to determine if maternally administered cimetidine interfered with the development of the male offspring's sex-dependent, hepatic drug-metabolizing enzymes. Cimetidine was administered in the mothers' drinking water at several levels reflecting both human and rat therapeutic-like doses from day 17 of gestation through day 7 of lactation. With the exception of a 30% decline in the Vmax for hexobarbital hydroxylase during adulthood, the developmental profile of microsomal drug-metabolizing enzymes, when measured at 1, 4 and 18 weeks of age, was generally unaffected by perinatal exposure to cimetidine. Furthermore, the levels of various components of the hepatic mono-oxygenase system (i.e. heme, cytochromes P-450 and b5, hexobarbital hydroxylase and p-chloro-N-methylaniline demethylase) following orchidectomy and androgen replacement at physiologic and inductive concentrations, were basically the same in control and cimetidine-exposed rats.

Comparative antiulcer and antisecretory effects of various calcium antagonists

1. The antiulcer activity (ethanol or indomethacin-induced ulcers) and the antisecretory effects (pylorus-ligated rats) of various selective and non selective calcium antagonists were studied. 2. Flunarizine and pirenzepine reduce the ethanol-ulcer length whereas diltiazem and cimetidine are weakly active and verapamil, nifedipine and nicardipine are ineffective. 3. All tested compounds except verapamil prevent the development of indomethacin-induced ulceration. 4. All substances, except flunarizine decrease the total H+ output in Shay rats. 5. The activities of the different compounds are discussed in terms of their mode of action.

Novel method for producing standard subacute gastric ulcer in rats and for the quantitative evaluation of the healing process. Effect of several drugs on healing

A simple new method has been developed for producing subacute gastric ulcers in rats, and it has been combined with a novel method for the quantitative evaluation of the healing process. Fasted rats of body weight 120-150 g were used. The animals were anaesthesized by ether and then a polyethylene catheter was orally inserted in the stomach with a fine needle inside. After the cannula reached the gastric wall, the needle was pressed gently so as to punch the tastric wall. Drugs under study were administered orally 30 min and 24 hr after the puncture. Food and water were given ad libitum from 2 hr after the intervention until the end (96 hr) of experiments. In order to follow the healing process of subacute ulcer, the so-called tensile strength of the ulcer was determined by inflating and was expressed in mmHg. The healing rate was calculated. The antiulcer drugs, cimetidine, famotidin, pirenzepine, and sucralfate, dose dependently and significantly increased the healing rate of ulcer. Nonsteroidal antiinflammatory drugs, naproxen, piroxicam, indomethacin, and ibuprofen, significantly delayed the healing of ulcer and acetylsalicylic acid showed no significant effect on the healing. Strong HCl (0.5 molar) significantly delayed the healing of ulcer. N-EM given subcutaneously dose dependently delayed the healing of subacute ulcer.

The effect of cimetidine on chronic gastric ulcers in rats

Surgically induced chronic gastric ulcers were created in rats. Cimetidine was administered for 1 year and the histological features of the gastric mucosa were studied to determine if cimetidine induced greater than normal proliferative or metaplastic changes or atypia. There were 60 rats in the study group and 51 and 55 in two control groups. The incidence of persisting chronic gastric ulcer in the cimetidine-treated study group at 1 year was 45% compared with 58% in non-treated control group (non-significant difference). There was no tendency for proliferative or metaplastic changes to be associated with cimetidine treatment--these changes reflected the presence of the chronic ulcers. Cimetidine did not induce atypia and no cases of gastric carcinoma occurred.

Luminal acid in stress ulceration and the antiulcer action of verapamil in rat stomachs

The role of luminal acid and the influence of the antisecretory action of verapamil in stress ulcer prevention in rat stomachs have been studied. Intraperitoneally injected verapamil, 4 mg kg-1, inhibited gastric acid secretion and ulcer formation, however, a 2 mg kg-1 dose, which did not significantly influence acid output, also had an antiulcer effect. Intraperitoneal injection of bethanechol, 1.2 or 3.6 mg kg-1, increased gastric acid output, but did not influence stress-induced ulcer formation. Oral administration of HCl, 25 or 50 mu equiv, aggravated stress ulceration in a dose-dependent manner; this lesion-worsening effect was prevented by pretreatment with verapamil or bethanechol. The gastric luminal acid content in 2 h pylorus-ligated rats was similar in the groups given either bethanechol or HCl. These findings indicate that the antisecretory action of verapamil may not account for its antiulcer effect. It is suggested that endogenous and exogenous luminal acid may have different influences on stress ulcer formation.

Gastric antisecretory, gastric and duodenal anti-ulcer and cytoprotective properties of Ro 22-6923, a synthetic trimethyl prostanoid in rats

Ro 22-6923, a synthetic trimethyl prostanoid, has been studied for its ability to inhibit gastric secretion and to protect the gastroduodenal mucosa against the injuries caused by pyloric ligation, hypothermic restraint stress, nonsteroidal anti-inflammatory drugs (NSAIDs), reserpine, dimaprit, cysteamine and the cytodestructing agents--80% ethanol, 0.6 M HCl, 0.2 M NaOH, 25% NaCl, aspirin 30 mg in 0.35 M HCl and 100 mM sodium taurocholate in 0.2 M HCl. The results of this study demonstrate that Ro 22-6923 has both prophylactic and curative effects on various experimental models. It produces a dose dependent inhibition of the gastric mucosal damage induced by pyloric ligation, hypothermic restraint stress, NSAIDs, reserpine, dimaprit and cytodestructing agents and that of duodenal ulcers induced by cysteamine. It also produces a dose dependent healing of the acetic acid induced chronic gastric ulcers. These observations suggest that Ro 22-6923 exerts its anti-ulcer effects by its antisecretory, gastric mucosal resistance increasing and cytoprotective activities and that it may be a useful therapeutic agent for the treatment of peptic ulcer disease in humans.

Antiulcer effect of (-)-cis-2,3-dihydro-3-(4-methylpiperazinylmethyl) -2-phenyl-1,5-benzothiazepin-4-(5H)-one hydrochloride (BTM-1086) in experimental animals

Effects of (-) cis-2,3-dihydro-3-(4-methylpiperazinylmethyl)-2-phenyl-1,5-benz othiazepin-4-(5H ) -one hydrochloride (BTM-1086) on various experimental gastric and duodenal ulcers were studied in rats. In the pylorus-ligated ulcer, restraint and water immersion stress ulcer, and drug-induced ulcer (indomethacin, aspirin, reserpine, serotonin, cysteamine), BTM-1086 prevented the development of ulcer at a dose of 0.1 to 1 mg/kg, p.o., but only weakly inhibited the histamine-induced gastric ulcer. The inhibitory activities of BTM-1086 were significantly higher than those of atropine sulfate. In the healing experiment with the acetic acid-induced stomach ulcer, BTM-1086 (1 mg/kg/day, p.o., X 14) showed a significant healing effect, which was higher than that of propantheline bromide. BTM-1086 at a dose of 0.2 mg/kg, i.d., remarkably inhibited the gastric secretion 6 hr after pylorus ligation. The aspirin-induced reductions of the total acid and K+ as well as the increments of the volume and Na+ in the gastric secretion were prevented dose-dependently by pretreatment with BTM-1086.

The influence of morphine on acid secretion by the isolated rat gastric mucosa

The influence of morphine on acid secretion by the isolated gastric mucosa was studied in adult rats. A wide range of morphine concentrations (1 X 10(-4) to 1.6 X 10(-3) M) was found to have no effect on basal acid output, or on acid secretion maximally stimulated by bethanechol or histamine. It is suggested that the opiate receptors in the rat gastric mucosa, if there are any, are not involved in modulating acid secretion.

The influence of verapamil on the gastric effects of stress in rats

The influence of verapamil on stress- or bethanechol-induced gastric effects was investigated in rats. Intraperitoneally injected verapamil (1, 2 or 4 mg/kg), given 30 min beforehand, dose-dependently prevented gastric glandular ulceration, mast cell degranulation and the increased stomach wall contractions evoked by restraint at 4 degrees C for 1 h. Gastric acid secretion, as well as ulceration in both the forestomach and glandular segment, produced by subcutaneously-injected bethanechol (3.2 mg/kg) were also inhibited. It is concluded that decreased amine release from the mast cells, stomach wall relaxation and reduced gastric acid were responsible for the ulcer-antagonising effects of the calcium-entry blocker. The possible antiulcer actions of verapamil are discussed in the light of present knowledge regarding calcium involvement in the various mechanisms thought to contribute to the pathophysiology of stress ulceration in rat stomachs.

Histidine decarboxylase inhibition: a novel approach towards the development of an effective and safe gastric anti-ulcer drug

The involvement of histamine in mediating gastric function under normal and pathological conditions has been largely established. The relationship between gastric acid production and peptic ulcer diathesis is also well known. Recently, endogenous histamine formation and its release from mast cells has been implicated in the pathogenesis of human and experimental gastric ulcers produced by restraint and pyloric ligation. It has also been implicated in the gastric mucosal damage produced by drugs like aspirin, phenylbutazone and reserpine. These observations suggest that histidine decarboxylase inhibitors may be useful in the prevention of such lesions. Our studies on the evaluation of some histidine decarboxylase inhibitors show that these compounds have a promising potential for developing an effective and safe anti-ulcer drug. This mini-review incorporates the results of our studies which have been adequately supported by other studies as well.

Effect of cimetidine and carbenoxolone on cysteamine-induced ulcers: a study of gastric mucosal histamine and histamine formation capacity in rat

Cysteamine-induced ulcers in rat were used to study the effect of ulcer-healing agents with different modes of action on ulcer formation and mucosal histamine. Male Wistar rats were divided into 5 groups. Group I had cysteamine injection; group II had cimetidine followed by cysteamine injection; group III had carbenoxolone before cysteamine injection; group IV had carbenoxolone as group III and cimetidine and cysteamine injections; group V had saline injections (controls). In group I 20/29; group II 17/30; group III 15/29; and group IV 23/30 developed ulcers. No significant differences were found. No ulcers were found in group V. Comparison between all groups and controls showed an increase in gastric mucosal histamine and HFC. The increase in histamine was related to ulcer formation. Duodenal and oesophageal histamine did not change significantly. Gastric mucosal histamine and HFC were directly correlated.

The gastric antisecretory activity of 3-methoxy-5,7,3'4'-tetrahydroxyflavan (ME)--a specific histidine decarboxylase inhibitor in rats

3-Methoxy-5,7,3'4'-tetrahydroxyflavan (ME), a specific histidine decarboxylase inhibitor, has been shown to significantly reduce the gastric acid secretion and gastric tissue histamine levels in 6 h pylorus ligated rats. It has been found to be as effective as cimetidine in reducing the gastric acid secretion. However, cimetidine does not affect the gastric tissues histamine levels in the normal or pylorus ligated rats. These observations clearly establish that the two drugs reduce the gastric acid secretion by different mechanisms and suggest that their combination may show a potentiated gastric anti-ulcer activity.

Gastric secretory conditions and plasma gastrin levels in rats after prolonged treatment with cimetidine

Effects of 4 weeks of treatment with oral cimetidine, 100 mg/kg twice daily, on gastric secretion and plasma gastrin levels were studied in rats. Pylorus ligation-induced and pentagastrin-stimulated gastric secretions were little changed at days 1, 3, and 10 after cessation of cimetidine treatment as compared to the controls. Histamine-stimulated acid secretion was significantly higher in the cimetidine-treated group than in the controls at day 3 after cimetidine treatment but was unchanged at days 1 and 10. A single oral administration of cimetidine at 100 mg/kg significantly increased plasma gastrin levels 4 hr after the treatment in refed rats but not at 2 and 8 hr later. Plasma gastrin levels significantly decreased at days 3 and 10 after cessation of cimetidine treatment as compared to the controls. Thus, while prolonged treatment with cimetidine induces a transient increase in response of parietal cells to histamine and a reduction of food-stimulated gastrin release, it does not seem to induce other appreciable changes in gastric secretion.

Effects of an antiulcer drug, sucralfate (a basic aluminum salt of sulfated disaccharide), on experimental gastric lesions and gastric secretion in rats

The effects of oral sucralfate, a basic aluminum salt of sulfated disaccharide, on various experimental gastric lesions and on gastric secretion were studied in rats. Sucralfate at 300 mg/kg potently inhibited the development of Shay ulcers and indomethacin- and aspirin-induced erosions. The drug at 1000 mg/kg also potently inhibited histamine-induced erosions. Water-immersion stress-induced erosions were inhibited with 1000 mg/kg of the drug, but the degree of inhibition was weaker than that seen in other types of erosion formation. Sucralfate at 1000 mg/kg given twice daily for 14 days significantly accelerated the spontaneous healing of acetic acid-induced ulcers. Sucralfate at over 300 mg/kg tended to increase the volume of gastric juice but had an insignificant effect on acid and pepsin output of pylorus-ligated rats. As a whole, the effects of sucralfate on experimental gastric lesions appear to be much more potent than Maalox, propantheline bromide, and cimetidine. The mechanism of action of sucralfate remains to be determined.

Cimetidine and parietal cell regeneration in experimental wounds in rat gastric mucosa. A light and electron microscopic study

Cimetidine, 75 mg/kg body weight, was given twice daily by gastric tube to rats with experimental gastric ulcers. After 130 days' treatment the rats were killed, and sections from the wounds and normal mucosa were prepared for light and electron microscopy. Light microscopic studies showed that the regenerating mucosa in the wounds was thicker in the cimetidine-treated animals than in the controls. Stereological analyses demonstrated no differences in mean size of the parietal cells or in parietal cell volume density between the cimetidine-treated and the untreated groups, but an increase in the secretory surface density was detected in the parietal cells from rats that had been given cimetidine.

Histamine H2-antagonists modify gastric emptying in the rat

1 Histamine H2-receptor antagonists were tested for their effect on gastric emptying in the rat. 2 At low doses all the compounds were inactive except for burimamide which delayed and ranitidine which accelerated gastric emptying. 3 At high doses burimamide, metiamide, cimetidine and oxmetidine delayed, whereas ranitidine accelerated gastric emptying; tiotidine remained ineffective. 4 Changes in emptying rate were not accompanied by changes in emptying pattern which, with all the compounds examined, proceeded, as in the controls, by apparent first order kinetics. 5 The mechanism of the ranitidine-induced acceleration of gastric emptying seemed to be connected with an interference with the cholinergic system, whereas the mechanism of cimetidine- and oxmetidine-induced slowing of gastric emptying was apparently related to cholinolytic and possibly also relaxant effects of the compounds. 6 These different effects of the various H2-blockers are consistent with the idea that changes in emptying rate are independent of H2-receptor blockade.

Different effects of the H2-antagonists on gastric emptying in the rat

H2-receptor antagonists, in doses capable of inhibiting gastric secretion, did not generally affect gastric emptying. Exceptions were burimamide, which delayed the emptying rate, and ranitidine, which accelerated it. At higher doses burimamide, metiamide cimetidine and oxmetidine delayed gastric emptying, but ranitidine accelerated it to a greater extent. Tiotidine remained ineffective. These data suggest that changes in emptying rate are independent of the H2-receptor blockade.

The influence of cimetidine, a histamine H2-receptor antagonist, on the gastric effects of reserpine in rats

The effects of graded doses of cimetidine on both resting and reserpine-evoked gastric acid secretion were examined in relation to their influence on reserpine-induced ulceration, mast cell degranulation and mucosal microcirculatory changes in rat stomachs. Cimetidine 10 mg/kg or above reduced resting or reserpine-provoked gastric acid secretion as well as rumenal and glandular ulceration. However, non-acid-inhibiting doses, 5 mg/kg or below, continued to prevent glandular ulceration. Reserpine-evoked gastric glandular mucosal mast cell degranulation was unaffected by both acid-inhibiting and non-acid-inhibiting doses of cimetidine which dose-dependently blocked the superficial glandular mucosal microcirculatory volume changes. These results suggest that cimetidine prevents reserpine-induced glandular ulceration largely by blocking the ulcerogenic effect of histamine H2-receptor-mediated mucosal microcirculatory congestion, in contrast to antagonising rumenal lesions through acid inhibition; they also support the idea tha reserpine may release histamine mainly from the glandular mucosal mast cells. The possibility of another antiulcer mechanism, due to cytoprotection, is discussed.

Effects of cimetidine, atropine and prostaglandin E2 on rat mucosal erosions produced by intragastric distension

The effects of three typical antisecretory agents: cimetidine, atropine and prostaglandin E2 were compared on an acute rat gastric ulcer model which consisted of perfusing the stomach continuously, at a high intraluminal pressure (120 mm H2O), with a simulated gastric juice (0.1 M HCl plus 600 mg pepsin/l). As the acid and pepsin are given exogenously the inhibitory action of the antisecretory drugs is obviated in this model. Cimetidine and atropine failed to reduce gastric erosions, whereas prostaglandin E2 markedly reduced the severity of the mucosal lesions with respect to control values. Long-term treatment with cimetidine also failed to increase the resistance of the gastric mucosa to the digestive action of the artificial gastric juice. These findings indicate that only prostaglandin E2 is cytoprotective and do not support the view that anticholinergics or histamine H2-receptor antagonists have a cytoprotective role on the cells of the gastric mucosa.

The role of aspirin in gastric ulceration . Some factors involved in the development of gastric mucosal damage induced by aspirin in rats exposed to various stress conditions

The gastric irritant effects of aspirin were studied in rats treated with a variety of physical and "disease" (inflammatory) stress conditions (which may mimic responses to some stress states encountered clinically) with the object of establishing whether these stress states increase the susceptibility of the gastric mucosa to the potentially ulcerogenic actions of aspirin. While exposure to physical (eg, cold) stress conditions markedly increased the sensitivity of the gastric mucosa to aspirin, exposure to various disease stressors (eg, adjuvant arthritis, acute pain, or paw inflammation) did not appreciably affect the mucosal sensitivity to this drug. Attempts were made to determine the mechanisms of the physical stress plus aspirin interaction by use of pharmacological agents. The results suggest a major involvement of the parasympathetic-vagal, sympathetic, and histamine-producing systems, but not the adrenocortical axis, in this model of gastric ulcerogenesis. No differences were observed in the mucosal uptake of [14C]aspirin, showing that accelerated uptake of the drug is not a factor in the development of gastric ulceration.

Effects of cimetidine on healing of chronic gastric and duodenal ulcers in dogs

The effects of cimetidine on healing of gastric and duodenal ulcers induced in mongrel dogs were studied. Gastric ulcers were produced by subserosal injection of acetic acid solution and duodenal ulcers by topical application of acetic acid on the serosal surface of the duodenum. Oral treatment with cimetidine, 450 mg/dog/day in three divided doses for 14 days, produced a remarkable acceleration of healing of duodenal ulcers but exerted little influence on gastric ulcers.