A new model of stress ulcer in the rat with pylorus ligation and its pathogenesis

Acute and sub acute toxicity study on Sangu parpam

Peptic ulcer is described in the siddha system of medicinal classification of 4448 diseases. Information on the use of Sangu Parpam in treating peptic ulcer is known. Therefore, it is of interest to document the acute and sub acute toxicity analysis on Sangu parpam in this regard.

Ethanol-induced gastric ulcer in rats and intervention of tert-butylhydroquinone: Involvement of Nrf2/HO-1 signalling pathway

Gastric ulcer (GU) is the most common health concern that occurs due to alcohol consumption, smoking and physiological stress. Ethanol-induced GU in animal model resembles the pathophysiology of human ulcer. The present study was designed to investigate the cytoprotective and anti-inflammatory properties of tert-butylhydroquinone (tBHQ), a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, against gastric mucosal damage induced by acute exposure of ethanol (5 ml/kg). The intervention of tBHQ (25 and 50 mg/kg, per os (po)) and omeprazole (20 mg/kg, po) was done for 10 consecutive days. Omeprazole was chosen as a standard drug because it is prescribed for the treatment of GU. Pretreatment of tBHQ decreased gastric mucosal lesion, ulcer index, apoptotic cells and lipid peroxidation level induced by ethanol. Furthermore, the intervention of tBHQ increased gastric mucosa integrity, pH, reduced glutathione, collagen and mucus-producing goblet cells. Intervention of tBHQ increased the expression of antioxidant markers such as Nrf2, haeme oxygenase-1 and catalase and decreased the expressions of inflammatory markers such as nuclear factor kappa-light-chain-enhancer of activated B cells and cyclooxygenase-2. The cytoprotective potential of tBHQ against gastric mucosal damage might be due to its ability to enhance cellular antioxidants and anti-inflammatory responses.

Protective effects of Weilikang decoction on gastric ulcers and possible mechanisms

Although Weilikang decoction (WLK) has been used for gastric ulcer (GU) therapy in a clinical setting with good curative effect for >20 years, the mechanism remains unclear. Several GU animal models, induced by ethanol, hydrochloric acid, aspirin, pylorus ligation, acetic acid and indomethacin, were used to investigate the gastroprotective effects of WLK decoction. Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME), indomethacin, and N-ethylmaleimide (NEM) were pretreated, respectively, to investigate the action mechanism. Real-time polymerase chain reaction and Western blot analysis methods were used to determine the effects of WLK on indomethacin-induced GUs. The WLK-administered groups (2.5, 1.25 and 0.625 g/kg) significantly reduced the GU areas induced by ethanol, hydrochloric acid and aspirin. Furthermore, the effects could be quenched by L-NAME and NEM, but not by indomethacin. The 2.5 and 1.25 g/kg WLK groups showed significantly decreased effects on GU areas induced by pylorus ligation and acetic acid. WLK treatment significantly decreased mRNA expression on cyclooxygenase (COX)-1, COX-2, interleukin-6, tumor necrosis factor α and inducible nitric oxide synthase (iNOS) mRNA, but showed no effect on endothelial nitric oxide synthase mRNA expression. Western blot analysis result showed that WLK-treated groups markedly downregulated COX-2 protein expression. The anti-ulcer potential of WLK can be primarily attributed to its regulatory effects on nitric oxide, sulfhydryl compounds, and reduction effect on mucosal expression of proinflammatory cytokines.

Anti-ulcerogenic effect of chitin and chitosan on mucosal antioxidant defence system in HCl-ethanol-induced ulcer in rats

The anti-ulcerogenic effect of chitin and chitosan against ulcer induced by HCl-ethanol in male Wistar rats was studied. Levels of acid output, pepsin, protein, lipid peroxides and reduced glutathione and the activity of glutathione peroxidase (GPx), glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) were determined in the gastric mucosa of normal and experimental groups of rats. A significant increase in volume and acidity of the gastric juice was observed in the ulcer-induced group of rats. Peptic activity was significantly decreased as compared with that of normal controls. In the rats pre-treated with chitin and chitosan 2% along with feed, the volume and acid output and peptic activity of gastric mucosa were maintained at near normal levels. The level of lipid peroxidation was significantly higher in the ulcerated mucosa when compared with that of normal controls. This was paralleled by a decline in the level of reduced glutathione and in the activity of antioxidant enzymes like GPx, GST, CAT and SOD in the gastric mucosa of ulcer-induced rats. Also, the levels of mucosal proteins and glycoprotein components were significantly depleted in ulcerated mucosa. The pre-treatment with chitin and chitosan was found to exert a significant anti-ulcer effect by preventing all the HCl-ethanol-induced ulcerogenic effects in experimental rats.

Protective effect of glucosamine against ibuprofen-induced peptic ulcer in rats

BACKGROUND

Helicobacter pylori is the major causative factor of ulcer but the use of ibuprofen and other non-steroidal anti-inflammatory drugs have also been implicated in development of ulcer. The purpose of the present study was to determine the anti-ulcer effect of glucosamine.

METHODS

The protective effect of glucosamine on ibuprofen-induced peptic ulcer in male albino rats was studied with respect to changes in the volume of gastric juice, acid output, pepsin activity, activities of membrane bound ATPases, protein content, glycoprotein components and histopathology.

RESULTS

Oral administration of ibuprofen caused significant increase in the number of lesions in the gastric mucosa, increases in the volume of gastric juice and acidity, and decreased activity of pepsin. The levels of protein content and glycoprotein components (hexose, hexosamine and sialic acid) and ATPase activities were also observed. Oral pretreatment with glucosamine resulted in significant reduction in the number of lesions in the gastric mucosa and decreases in the volume of gastric juice and acidity. The pepsin activity was also maintained at near normalcy. Prior oral administration of glucosamine significantly prevented the ibuprofen-induced depletion of protein and glycoprotein components and maintained the activities of membrane bound ATPases as compared to untreated ulcer induced group of rats.

CONCLUSION

The anti-ulcerogenic activity of glucosamine might be ascribable to its ability to neutralize the hydrochloric acid secreted into the stomach and to its capability to strengthen the mucosal barrier by increasing mucosal glycoprotein synthesis and to its free radical scavenging property. Histopathological investigations of the mucosal tissue also support the anti-ulcerogenic effect of glucosamine.

Efficacy of brown seaweed hot water extract against HCl-ethanol induced gastric mucosal injury in rats

Effect of pre-treatment with hot water extract of marine brown alga Sargassum polycystum C.Ag. (100 mg/kg body wt, orally for period of 15 days) on HCl-ethanol (150 mM of HCl-ethanol mixture containing 0.15 N HCl in 70% v/v ethanol given orally) induced gastric mucosal injury in rats was examined with respect to lipid peroxides, antioxidant enzyme status, acid/pepsin and glycoproteins in the gastric mucosa. The levels of lipid peroxides of gastric mucosa and volume, acidity of the gastric juice were increased with decreased levels of antioxidant enzymes and glycoproteins were observed in HCl-ethanol induced rats. The rats pre-treated with seaweed extract prior to HCl-ethanol induction reversed the depleted levels of antioxidant enzymes and reduced the elevated levels of lipid peroxides when compared with HCl-ethanol induced rats. The levels of glycoproteins and alterations in the gastric juice were also maintained at near normal levels in rats pre-treated with seaweed extract. The rats given seaweed extract alone did not show any toxicity, which was confirmed by histopathological studies. These results suggest that the seaweed extract contains some anti-ulcer agents, which may maintain the volume/acidity of gastric juice and improve the gastric mucosa antioxidant defense system against HCl-ethanol induced gastric mucosal injury in rats.

The antiulcer activity of Garcinia cambogia extract against indomethacin-induced gastric ulcer in rats

Garcinia cambogia extract is a herbal preparation that has been suggested as useful in the treatment of gastrointestinal disorders. In the present study this drug was tested for its antiulcerogenic effect. Oral pretreatment with Garcinia cambogia fruit extract (1 g/kg body wt/day) for 5, 10 or 15 days protected the gastric mucosa against the damage induced by indomethacin (20 mg/kg body wt). The volume and acidity of the gastric juice decreased in the pretreated rats. The glycoprotein levels of the gastric contents which were decreased in the untreated rats, maintained near normal levels in the pretreated rats. Protein which was elevated in the gastric juice of untreated rats, showed near normal levels in the pretreated rats. Garcinia cambogia was able to decrease the acidity and to increase the mucosal defence in the gastric areas, thereby justifying its use as an antiulcerogenic agent.

Effect of psychogenic stress on gastrointestinal function

This review summarizes the studies published over the last twenty years on the effects of psychogenic stress on gastrointestinal function, using animal models. The effects of stress on gastric ulceration have received wide attention and the central and local mechanisms of mucosal damage have been, for the most part, clearly delineated. In comparison, relatively few studies have focused on the impact of stress on intestinal and colonic physiology, even though its influence on intestinal motility, mucosal permeability and inflammation has been established. More work is necessary in this field, especially considering the importance of irritable bowel syndrome in modern society.

Characterization of dopamine receptor subtypes involved in experimentally induced gastric and duodenal ulcers in rats

There are conflicting reports about the role of dopamine in gastric and duodenal ulcers. This investigation was undertaken to characterize the specific subtypes of dopamine receptor involved in gastric and duodenal ulceration. Administration of dopamine D1 agonist fenoldopam and dopamine D2 antagonist sulpiride elicited a significant decrease in acid secretion, total acid output, pepsin output and histamine content in the gastric juice, and reduced ulcer-index values, in pylorus-ligated rats. However, dopamine D1 receptor antagonist SCH 39166 ((-)-trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H -benzo (d) naptho -(2,1-b) azepine) and the D2 receptor agonist quinpirole led to significant augmentation of these parameters compared with respective controls. In the restraint plus water-immersion stress model the score for intraluminal bleeding and the cumulative gastric lesion length was significantly lower for rats treated with fenoldopam and sulpiride. The opposite effects were observed after pretreatment of rats with SCH 39166 and quinpirole. In the cysteamine-induced duodenal ulcer model the mean ulcer area and the score for intensity were significantly lower for fenoldopam and sulpiride and higher for SCH 39166 and quinpirole. Our data suggest that the dopamine D1 and D2 receptors have opposite effects on gastric and duodenal ulcers. Whereas stimulation of dopamine D1 receptors inhibits the formation of gastric and duodenal ulcers, stimulation of dopamine D2 receptors has a pro-ulcerogenic effect.

Immobilization-induced and crowded environment-induced stress delay barrier recovery in murine skin

To examine the effect of stress on skin homeostasis, cutaneous barrier recovery was measured in rate exposed to immobilization stress after tape stripping or sodium dodecyl sulphate treatment. The barrier function was evaluated by measuring transepidermal water loss. Barrier recovery was delayed in rats exposed to stress in comparison with untreated controls. This tendency was observed in both male and female animals. The delay in barrier recovery was blocked by application of the sedative drugs diazepam and chlorpromazine. The barrier recovery rate in mice which were kept at a high population density (10 animals per cage) for 2 weeks was slower than that in mice kept at lower population densities (five animals or one animal per cage). These animal models could be useful for objectively quantifying the influence of stress on the cutaneous function.

Anti-ulcerogenic evaluation of the methanolic extracts of some indigenous medicinal plants of Pakistan in aspirin-ulcerated rats

Anti-ulcerogenic activity of the methanolic extracts of 4 medicinal plants were studied in aspirin-induced gastric ulcers in rats. Their effects on the volume of gastric juice secreted, acid output, peptic activity, mucin activity and curative ratio were recorded. Bauhinia racemosa (flower buds) decreased the ulcer index significantly, and Moringa pterygosperma (flower buds) showed some decrease in the ulcer index. Trianthema pentandra (whole plant) did not show any decrease in the acid or pepsin content or any increase in mucin; however, it showed a highly significant decrease in the ulcer index. Cordia latifolia (ripened fruit) did not however decrease the ulcer index.

Biochemical evaluation of the antiulcerogenic effect of Cauvery-100 (an ayurvedic formulation) in rats

Due to the varied pathogenesis of ulcers, a number of pharmacologically different antiulcer drugs are now used in the treatment of the condition. The suitability of certain of these drugs is still to be established. Cauvery-100 is an ayurvedic formulation consisting of plant ingredients, and has been suggested to be useful in the treatment of gastrointestinal disorders. In the present study this drug was tested for its antiulcerogenic effect. The number of lesions on gastric mucosa decreased markedly after 15 days oral treatment with Cauvery-100 in rats with indomethacin-induced ulcers. The volume and total acidity of the gastric juice also decreased in the treated rats. The hexose, hexosamine and sialic acid levels of gastric contents, which were increased in untreated rats returned to near normal levels after 15 days of treatment. Protein in the gastric juice was elevated in untreated rats but returned to near normal levels after 15 days of treatment. Cauvery-100 acts both to decrease the acidity and to increase the mucosal defence in the gastric areas, thereby justifying its use as an antiulcerogenic agent.

Sex differences and stress response of WKY rats

Wistar Kyoto (WKY), Fischer-344 (F-344), and Wistar male and female rats during either proestrus-estrus or diestrus phases of the estrus cycle were exposed to the ulcerogenic procedure of water restraint. Both male and female WKY rats revealed significantly more stomach ulcers as compared to Wistar and F-344 rats of the same sex. No persistent sex difference was observed, but ulcer severity was more pronounced during the proestrus-estrus phase as compared to the diestrus phase of the estrus cycle particularly in WKY female rats. In the second study, WKY females were observed as more active in the open-field test (OFT), but more immobile in the forced swim test (FST), as compared to WKY male rats. In addition, proestrus-estrus WKY females were less active in the OFT and significantly more immobile in the FST as compared to diestrus females. Thus, proestrus-estrus WKY females were judged as more emotional in the OFT and as exhibiting more signs of behavioral depression according to the FST. These studies suggest that the steroid hormone milieu in WKY rats may be responsible for these behavioral changes as well as the stress responsiveness in this stress-susceptible rat strain.

Parallelism among stress effects on ulcer, immunosuppression and analgesia: commonality of mechanisms?

Some general principles and mechanisms have been discovered that govern proactive effects of one stress on animals' later stress or challenge induced behavior, nociception, immune function, and stomach ulcerations. As described below, these principles demonstrate a considerable degree of parallelism across the domains represented by measures of learning deficits and fear-related behaviors, hypoalgesia, immunological status and stress gastric ulcerations. At a minimum, these parallels suggest that operational factors found important in one domain are likely factors of importance in the other domains. Beyond this, these parallels are permissive of an inference of commonality in underlying processes. Nonetheless, results reviewed below suggest that the specific response of the organism to stress is highly dependent on specific characteristics of the stressor.

Strain, age, but not gender, influence ulcer severity induced by water-restraint stress

Two ulcerogenic procedures, supine restraint (SR) and water restraint (WR) were compared. In Experiment 1, Fischer-344 (F344), Sprague-Dawley (S-D), Wistar, Long-Evans (L-E), Spontaneously Hypertensive rats (SHR) and Wistar Kyoto normotensive (WKY) rats were exposed to SR and WR. WR produced more ulcers than SR. There was no difference in ulcer scores between WKY, F344 and L-E but these rats had significantly more ulcers as compared to SHR, Wistar and S-D rats. In Experiment 2, 4- and 16-month-old SHR, WKY and F344 rats were exposed to SR and WR. The older WKY rats had more ulcers than all other treatment groups. Experiment 3 revealed no significant differences between male and female rats exposed to either SR or WR. Body temperature (BT) scores obtained after restraint and after 2-hr postrestraint rest were only marginally related to ulcer severity. Rats exposed to WR had lower BT scores but the strain and age ulcer differences did not have corresponding BT differences. These studies revealed the following: the ulcer susceptibility of WKY rats; the WR technique is a useful ulcerogenic procedure; and hypothermia is a weak covariant to restraint-induced stress ulcer.

Effects of gastric distension and prostaglandin on acid ethanol-induced mucosal lesions in the rat

The effects of gastric distension on the morphology of acidified ethanol (AE) -induced mucosal lesions and on the protective action of 16,16-dm PGE2 were investigated in rats. AE (50% ethanol in 150 mM HCl) was given by gavage in the intact stomach or through a fistula prepared in the forestomach in the pylorus-ligated stomach. AE produced elongated bands of hemorrhagic necrosis within 1 hr in the former, while in the pylorus-ligated stomach the shape of lesions varied depending upon the volume of irritant. One milliliter produced bandlike lesions, whereas 2 ml or more induced widespread lesions; such volumes were observed to remove the mucosal folds. 16,16-dm PGE2 (0.3-10 micrograms/kg, subcutaneous) dose dependently reduced bandlike lesions in the intact stomach, but had no or little effect on non-band-like lesions in the pylorus-ligated stomach. This agent (10 micrograms/kg) had a slight effect on the reduction of PD caused by 10-min exposure of the stomach to AE (2 ml) in the intact stomach, while such effects were not apparent in the pylorus-ligated stomach. Oral gentian violet (2 ml, 0.3% w/v) produced bandlike staining of the mucosa in intact rats, but the effect was blocked by pyloric ligation. 16,16-dm PGE2 also significantly prevented the localized staining pattern seen in intact rats.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of two ulcerogenic techniques

Long Evans rats 45, 130, or 280 days old were exposed either to a supine restraint or a water restraint treatment for two hr. This was followed by a 2-hr rest period. Core body temperature was recorded every 30 min. Stress-induced hypothermia was greatest in the water restraint treatment and in younger rats irrespective in both restraint conditions. The water restraint procedure as compared to the supine restraint produced significantly more ulcers in 130- and 280-day-old rats.

Importance of pepsin and stomach distension in morphological alterations of stress-induced gastric lesions in pylorus-ligated rats

Pylorus ligation changed the morphology and location of gastric lesions induced by water-immersion stress (WI stress) in rats; linear lesions in the corpus mucosa disappeared, and punctate lesions appeared in both the corpus and antrum, in association with the loss of H+ and the gain of Na+ in the gastric contents. Oral administration of antipeptic drugs such as amylopectin sulfate and sulfated glyptide or porcine pepsin significantly prevented or aggravated the lesions, respectively, although another type of elongated lesion appeared in response to high doses of antipeptic drugs. These antipeptic drugs or exogenous pepsin significantly reduced or increased pepsin activity, respectively, without effect on the acid output. Similar punctate lesions were produced in the atropinized rats (10 mg/kg) by instillation of acid solution (100 mM HCl plus 54 mM NaCl) with pepsin into the pylorus-ligated stomach and subjecting to WI stress. On the other hand, when the gastric contents were drained through a fistula to prevent accumulation of gastric juice in the pylorus-ligated stomach, WI stress again induced linear lesions only in the corpus mucosa. Acid hypersecretion in these rats induced by intravenous infusion of histamine, tetragastrin, or carbachol significantly aggravated the severity of lesions but did not change their morphology. These results suggest that pepsin in the presence of acid is prerequisite for development of gastric lesions in pylorus-ligated rats induced by WI stress. The morphological alterations may be accounted for by the distensions of the stomach due to accumulation of gastric juice in the lumen caused by pylorus ligation, but not due to acid hypersecretion.

Induction of duodenal ulcers in rats under water-immersion stress conditions. Influence of stress on gastric acid and duodenal alkaline secretion

We investigated the influence of stress on gastric acid and duodenal HCO3- secretion in rats, and examined whether duodenal ulcers develop in rats under stress conditions in the absence or presence of acid hypersecretion caused by histamine. Either restraint alone or restraint plus water-immersion stress induced lesions in the stomach but not in the duodenum. However, subcutaneous administration of histamine dihydrochloride (40 mg/kg every 2.5 h for a total of three times) to stressed rats produced macroscopically visible damage in the proximal duodenum as well as in the stomach within 8 h of exposure to stress, and the incidence of duodenal lesions was 100% in the water-immersion group (24.8 +/- 3.8 mm2, n = 8). Histamine alone had no effect on either region. These lesions in the duodenum caused by water immersion plus histamine were prevented by subcutaneously administered cimetidine (30, 100 mg/kg) or 16,16-dimethyl prostaglandin E2 (10, 30 micrograms/kg) in a dose-related manner, but not by atropine (1, 3 mg/kg). Restraint decreased acid secretion by 40%, and additional water immersion restored the decreased acid secretion to normal levels. Basal duodenal HCO3- secretion was decreased to about 70% of normal values (5-6 microEq/15 min) in the restraint group, and after additional water immersion further declined to the values of 1.5-2 microEq/15 min. An increase of HCO3- secretion caused by acid was significantly inhibited by water immersion but not by restraint. Histamine significantly increased acid secretion but did not affect duodenal HCO3- secretion. In the rats treated with both water immersion and histamine, acid secretion was significantly reduced by either cimetidine (100 mg/kg) or 16,16-dimethyl prostaglandin E2 (30 micrograms/kg), whereas duodenal HCO3- secretion was significantly increased by 16,16-dimethyl prostaglandin E2. Atropine had little effect on either acid or HCO3- secretion. These results suggest that exposure of rats to stress decreases duodenal HCO3- secretion and increases the susceptibility of the mucosa to acid emptied from the stomach, thereby inducing duodenal ulcers if acid hypersecretion is concomitantly present.

Gastric acid secretion and lesion formation in rats under water-immersion stress

In attempts to investigate the roles of acid in the pathogenesis of stress-induced gastric lesions, gastric acid secretion was studied in pylorus-ligated and lumen-perfused rats under restraint alone (R) or restraint with additional water immersion (WI). Gastric mucosal blood flow (GMBF) was measured with the aminopyrine clearance method in acute fistula rats. Acid secretion in pylorus-ligated rats significantly decreased under R or WI of either 3.5 or 7 hr stress. In the lumen-perfused or acute-fistula rats, exposure of rats to stress for 7 hr produced a similar decrease; however, in the WI group, there was a significant increase of acid secretion for 3-4 hr during stress, but not exceeding the prestress level. Only in the WI group did GMBF exhibit similar increases to those of acid secretory activity, and these increases were significantly inhibited by intraperitoneal administration of atropine (1 mg/kg) or cimetidine (60 mg/kg). Gastric lesions developed in both groups at 3.5 hr and became extensively severe at 7 hr only in the WI group. Cimetidine failed to influence the formation of lesions at 3.5 hr but significantly inhibited the later outgrowth of lesions at 7 hr, while atropine or pylorus ligation all but completely prevented lesions induced by either 3.5- or 7-hr WI stress. These results indicate that exposure of rats to stress (R or WI) generally decreased acid secretory activity, but there was a rise in acid secretion toward normal levels during WI stress, which may play an important role in the aggravating process of stress-induced gastric lesions.

Inhibition of gastric motor activity by 16,16-dimethyl prostaglandin E2. A possible explanation of cytoprotection

Effects of 16-dimethyl prostaglandin E2 (16-dmPGE2) and necrotizing agents on gastric motility and gastric mucosa were studied in conscious rats. Gastric motility was determined using a miniature balloon positioned in the glandular part of the stomach, which was connected to a pressure transducer and polygraph. Necrotizing agents, such as absolute ethanol, 0.6 N HCl, 0.2 N NaOH, or 4 M NaCl, were instilled into the stomach through a small fistula prepared in the forestomach. One milliliter of these agents produced streak lesions in the glandular part of the stomach within 1 hr, which were preceded by violent gastric contraction in every case. An intragastric administration of 16-dmPGE2 (0.3-3 micrograms/kg) by itself increased a tonus of the gastric wall but dose-dependently lessened the number and the amplitude of contractions. In those rats treated with 16-dmPGE2 (3 micrograms/kg), necrotizing agents failed to enhance the motility or to induce streak lesions. Pretreatment with 1 M NaCl as a mild irritant also inhibited gastric motility and lesion formation, but those actions were significantly antagonized by indomethacin (5 mg/kg). These results indicate that necrotizing agents induce a violent gastric contraction, followed by development of lesions in the stomach, and that the inhibition of gastric hypercontraction may be involved in a cytoprotective action of a prostaglandin against those induced gastric lesions in rats.

Effects of catecholamine agonist and antagonist drugs on acute stomach ulceration induced by medial hypothalamic lesions in rats

In order to investigate the involvement of catecholamines (CAs) in acute stomach ulceration induced by hypothalamic lesions, rats were given bilateral electrolytic anodal lesions in the medial hypothalamus followed by a single subcutaneous injection of CA agonist or antagonist drugs. As in previous studies, lesioned rats that received no post operative drug treatment showed extensive gastric damage when examined 24 hr after the brain lesion. Chlorpromazine, amphetamine, desipramine and isoproterenol caused significant reductions in the extent (total length) and/or number of erosions induced by the brain lesion. Haloperidol and propranolol did not seem to affect ulcer formation. Clozapine increased the number but not the total length of ulcers. Phentolamine, alone or in combination with propranolol, significantly increased both the number and total length of lesion-induced ulcers. Similarities between these results and those reported for most of these drugs in the context of ulcers induced by various experimental stress procedures suggest a degree of commonality between acute stress ulcers and ulcers induced by hypothalamic lesions. The overall pattern of results obtained is also consistent with evidence indicating a protective role for catecholamines in acute ulcer formation.

Effects of cholestyramine and synthetic hydrotalcite on acute gastric or intestinal lesion formation in rats and dogs

Cholestyramine, a bile-binding agent, markedly inhibited the development of gastric lesions induced by water-immersion stress in rats and of gastric and intestinal lesions induced by indomethacin in rats and dogs with an intact pylorus. However, cholestyramine had no effect on gastric lesions induced by stress in pylorus-ligated rats and on aspirin-induced gastric lesions in rats and dogs with or without pylorus ligation. Hydrotalcite, a potent antacid, significantly inhibited the gastric lesions induced by stress and aspirin in rats and dogs with or without pylorus ligation. Hydrotalcite also inhibited the gastric lesions induced by a single administration of indomethacin in rats with an intact pylorus. In contrast, the agent had no effect on gastric and intestinal lesions induced by repeated administration of indomethacin to rats and dogs with an intact pylorus. These results suggest that while bile probably plays an important role in the pathogenesis of stress-induced gastric lesions and of indomethacin-induced gastric and intestinal lesions, bile does not appear to play a role in the pathogenesis of aspirin-induced gastric lesions.

Effects of water-immersion stress on gastric secretion and mucosal blood flow in rats

The correlation between acid secretion and mucosal blood flow in the rat stomach during stress loading was determined to provide clues to the etiology of the gastric ulceration which thus occurs. The gastric acid output was increased remarkably by water-immersion stress at 23 degrees C, and this increase lasted while the stress was given, yet the mucosal blood flow did not show a corresponding increase. In rats stressed for 3 hr, ulcerative changes were observed in the glandular portion of the stomach. The stress-induced increase in acid output correlated well with the severity of erosions. Pretreatment of animals with atropine 10 microgram/kg, given subcutaneously, or vagotomy, inhibited the increase in acid output and also inhibited the ulcer formation caused by the stress: however, the mucosal blood flow in these animals decreased significantly. These results suggest that when there is an elevation of gastric acid secretion with no parallel increase in mucosal blood flow, gastric ulceration may occur under conditions of stress.

Effects of cimetidine, a histamine H2-receptor antagonist, on various experimental gastric and duodenal ulcers

The effects of cimetidine, a new histamine H2-receptor antagonist, on the development of experimental gastric and duodenal ulcers were studied. It was found that either by the oral, intraduodenal, or intraperitoneal route this agent had a marked inhibitory activity on stress-, aspirin-, indomethacin-, or histamine-induced gastric ulcers in rats and guinea pigs. The effects of cimetidine on stress-, aspirin-, and indomethacin-induced gastric ulcers were dose-dependent in many cases. Pylorus-ligation uclers, reserpine- or serotonin-induced gastric ulcers were little influenced by cimetidine. Duodenal ulcers induced by continuous infusion of carbachol-histamine were significantly inhibited by a simultaneous infusion of cimetidine. An analysis of gastric contents in pylorus-ligated rats after stressing indicated a decreased volume and acid output as the result of intraduodenal cimetidine treatment. In contrast, cimetidine exerted little influence on gastric secretion in rats treated with aspirin or in guinea pigs treated with histamine. Thus, the mechanism of action of cimetidine in preventing gastric or duodenal ulcers is likely to occur by suppression of gastric secretory function in a duodenal ulcer model but by suppression of other unknown ulcerogenic factors in gastric ulcer models.