Verapamil attenuates stress-induced gastric ulceration

Effect of (+/-)-verapamil and hydralazine on stress- and chemically-induced gastric ulcers in rats

The influence of (+/-)-verapamil and hydralazine on stress- and various chemically-induced gastric ulcers in rats together with their influence on various biochemical parameters which affect the development of the induced ulcers was examined. Pretreatment of rats with (+/-)-verapamil (4-16 mg kg-1 orally) significantly decreased cold-stress-induced gastric ulcers and enhanced ethanol-induced ulcers. It did not affect indomethacin- (30 mg kg-1 orally) or reserpine- (5 mg kg-1 i.p.) induced ulcers. Pretreatment of the animals with hydralazine (1-10 mg kg-1 orally) significantly enhanced ethanol-, reserpine- and cold-stress-induced ulcers. It did not affect indomethacin-induced ulcers. Pretreatment of the animals with verapamil increased gastric mucus secretion, inhibited gastric acid secretion, decreased glutathione content and enhanced gastric lipid peroxidation whereas pretreatment of the animals with hydralazine significantly decreased gastric mucus secretion. Hydralazine did not affect gastric acid secretion, glutathione or gastric lipid peroxidation. The results of this study suggest that verapamil-induced protection against stress-induced ulcer may be due to its ability to suppress gastric acid secretion and to increase gastric mucus secretion. Its enhancement of ethanol-induced ulcers may be due to its ability to increase lipid peroxidation. The hydralazine-induced enhancement of the experimentally-induced ulcers may be due to its ability to suppress gastric mucus secretion.

Relationship between tissue calcium content and duodenal ulcer in the rat

Since the effect of cellular calcium on cell injury has been in question, this study focused on the relationship between tissue calcium content and cysteamine-induced duodenal ulcer. Rats treated with cysteamine showed a high frequency and severity of duodenal ulcer, and the calcium content in the duodenal mucosa was elevated. Furthermore, the level of calcium content in duodenal mucosa was positively associated with the severity of the duodenal lesion. Whereas administration of calcium increased duodenal ulcerative response to cysteamine, verapamil afforded protection against ulceration. We conclude that calcium accumulation in duodenal mucosa is related to duodenal ulceration induced by cysteamine.

Behavioral changes in cold-stressed mice related to a central calcium-dependent-catecholamine synthesizing system

An investigation was carried out regarding the mechanism of behavioral changes in mice elicited by cold stress. Cold stress was induced in adult male mice by restraining them from free action for 2 h at 4 degrees C. As the control test, mice were restrained from free action for 2 h at room temperature. The locomotor counts in cold-stressed mice were found to be lower than in controls. The counts in cold-stressed mice were increased by IP pretreatment with EDTA or alpha-methyltyrosine (tyrosine hydroxylase inhibitor), and were further decreased by IP pretreatment with CaCl2. On the other hand, serum calcium and brain calcium levels in cold-stressed mice were increased 15-30 min and 30 min, respectively, after restraint under cold temperatures, and returned to original levels 1 h after restraint. Also, the biochemical and immunohistochemical brain dopamine levels in cold-stressed mice were higher than in control mice. The increment of brain dopamine levels in the control mice was also observed by the administration of CaCl2. Furthermore, the ability of cold stress to enhance the dopamine level in mice brains was attenuated by IP pretreatment with alpha-methyltyrosine. In light of previous reports that central calcium activates catecholamine-synthesizing enzymes via a calmodulin-dependent system, it is suggested that cold stress enhances the brain calcium level, and then increased calcium enhances dopamine synthesis in the brain through a central calcium-dependent catecholamine synthesizing system. Subsequently, increased dopamine induces behavioral changes.

Chronic oral treatment with diltiazem or verapamil decreases isolation-induced activity impairment in elevated plus maze

Adult male Wistar rats were either socially isolated or group-housed for 6 weeks and then tested in an elevated plus maze. During isolation the rats received either water or two concentrations of the calcium channel inhibitors, diltiazem or verapamil, in drinking solutions (approximately 5 and 10 mg/kg daily). Isolated rats showed a significantly lower total number of arm entries, a lower percentage of open arm entries and negligible time spent therein than did group-housed animals. Verapamil, in the higher dose, prevented that effect of isolation. Treatment with diltiazem brought about a similar tendency, though the effect did not reach statistical significance. Chronic treatment of group-housed rats with either drug failed to influence their behavior in the plus maze. We conclude that certain calcium channel inhibitors may decrease the behavioral deficit in the elevated plus maze that follows chronic social isolation.

Nifedipine versus cimetidine in prevention of stress-induced gastric ulcers in rats

The effects of nifedipine and cimetidine on cold/restraint stress-induced gastric ulcers and glandular wall mast cell count were studied in rats. Two hours of restraint at 4 degrees C resulted in 90% ulceration rate in the glandular stomach with a decrease in glandular wall mast cell count in the mucosa, submucosa and muscle layer. Nifedipine in three doses (1, 5 and 10 mg/kg) administered i.p. 30 min before stress significantly and dose dependently prevented gastric ulceration and mast cell degranulation. Cimetidine, in doses of 50, 100 and 150 mg/kg, again administered 30 min before stress prevented only gastric ulceration dose dependently without a significant change in mast cell count. The results indicate that both nifedipine and cimetidine are equally effective to reduce gastric mucosal ulceration in response to stress. However, the unique effect of nifedipine to inhibit mast cell degranulation which was now clearly demonstrated may favour the potential value of this drug in the management of peptic ulcer disease in humans.

Prevention of stress-induced erosive gastritis by parenteral administration of arachidonic acid

Stress-induced mucosal ulcerations are associated with a decreased synthesis of mucosal prostaglandin (PG) E2. This phenomenon is poorly understood. To investigate whether it is due to a decreased availability of the necessary substrates to the mucosa, four groups of 10 Holtzman rats were studied: group 1 received normal saline by intraperitoneal (ip) injection; group 2 also received ip normal saline, then were submitted to stress, by the cold restraint method; group 3 received a solution of arachidonic acid (AA) ip; and group 4 also received ip AA, then were submitted to stress. After sacrifice, the number of gastric ulcerations were counted and specimens of nonulcerated mucosa were assayed for PGE2 by high-performance liquid chromatography; the mean numbers of ulcers were 0, 5.8, 0.8, and 3 and the mean levels of PGE2 were 55, 41, 125, and 62 pg/mg of wet tissue for groups 1, 2, 3, and 4, respectively. It is concluded that parenteral administration of AA reduces but does not completely eliminate stress-induced gastric ulcerations and that the stressed animals synthesized half as much PGE2 as the nonstressed ones after ip administration of equal amounts of AA, suggesting that stress reduces the availability of AA to the gastric mucosa, possibly by vascular spasm.

Effect of verapamil on the gastric mucosal level of PGE2 during stress

Prostaglandin E2 is one of the factors in the maintenance of gastric mucosal integrity and verapamil, a calcium channel blocker, has been shown to reduce gastric mucosal ulcerations during stress. To investigate whether this protective effect of verapamil is mediated via PGE2, four groups of 20 Holtzman rats were given either 1 ml of normal saline (NS) intraperitoneally (ip): 1 mg/kg of indomethacin (I) ip; 2 mg/kg of verapamil (V) ip or I followed by V. Then 10 animals from each group were submitted to stress by the cold-restraint method. After sacrifice, gastric mucosal ulcerations were counted and specimens of nonulcerated mucosa were assayed for PGE2 by HPLC. Stress-induced mucosal ulcerations were associated with a significant decrease in the gastric mucosal levels of PGE2 (from 64.2 to 32.7 pg; P less than 0.05). This effect was magnified by the administration of indomethacin (down to 21.0 pg). Verapamil significantly increased PGE2 levels both in the stressed (48.0 pg) and unstressed (99.9 pg) animals and significantly reduced ulcerogenesis when compared to either NS- or I-treated groups. This effect of verapamil was completely blocked by the administration of indomethacin. In conclusion, verapamil stimulates PGE2 synthesis and its protective effect against stress-induced mucosal damage seems to be mediated by PGE2.

Calcium channel modulators: effects on gastric function

Calcium is important in stimulus-secretion coupling in the gut. We therefore examined a dihydropyridine (nitrendipine), a phenylalkylamine (verapamil) and a benzothiazepine (diltiazem) calcium channel blocker as well as a calcium channel 'agonist', CGP 28392, in several models of gastric function. Nitrendipine significantly decreased stress-induced gastric lesions, but was far less efficacious against 100% ethanol-induced lesions. The anti-ulcer effects of nitrendipine were not reversible with indomethacin, sodium meclofenamate or N-ethylmaleimide. Nitrendipine also significantly reduced basal gastric acid output. Verapamil significantly reduced stress lesions in an indomethacin and meclofenamate-reversible manner, but worsened ethanol ulcers. Verapamil also decreased basal acid secretion. Diltiazem decreased stress lesions (indomethacin- and meclofenamate-reversible), worsened ethanol lesions and slightly reduced acid secretion. CGP 28392 exerted a modest stress gastroprotective effect, decreased ethanol lesions and reduced slightly basal acid secretion. A possible clinical role for gastric calcium channel blockade is raised by these results.

Verapamil and nifedipine effects on gastric acid secretion and ulcer formation in rats

The calcium channel antagonists verapamil and nifedipine were examined for their effects on conscious basal gastric acid output, stress ulcer formation and on ethanol-induced ulcers. Both compounds significantly reduced gastric acid secretion, however verapamil did so in a dose-related manner. Both verapamil and nifedipine significantly attenuated stress gastric ulcer formation. Nifedipine, at a dose of 32.0 mg kg-1, virtually abolished stress ulcers. Verapamil exacerbated, while nifedipine, at 32.0 mg kg-1, attenuated ethanol-induced gastric ulcers. The differential gastrointestinal effects of these calcium channel antagonists support the existence of multiple classes of calcium channels in the gut and suggest an important role for intracellular calcium and hence, its blockade, in gastric pathophysiology.

Stress ulcers: current understanding of pathogenesis and prophylaxis

Stress-related gastrointestinal bleeding is known to occur in approximately 25 percent of untreated seriously ill patients, but with appropriate prophylaxis is largely preventable. Since the treatment of stress bleeding is generally unsatisfactory and has a high mortality, routine prophylaxis should be instituted for susceptible patients. Multiple mechanisms contribute to stress ulcer formation, the most important of which appear to be mucosal ischemia and the inability to control back-diffused hydrogen. Antacids and histamine2-blocking agents are presently the cornerstone of effective prophylaxis, but because they have been implicated as contributors to nosocomial pneumonias due to bacterial overgrowth in the stomach, investigation is ongoing into such alternative prophylactic agents as sucralfate and prostaglandins that do not alter the normal gastric acidity. This article presents a review of the literature on the development and prevention of stress ulcer disease.

Protection by the calcium antagonist Wy-47,037 against stress ulceration in the rat

Wy-47,037, a novel compound with both intracellular and extracellular calcium-blocking properties, was evaluated for its effects on cold/restraint stress induced ulceration in the rat. Wy-47,037 dose-dependently inhibited ulcerogenesis; with an ED50 of 8 mg/kg, PO, it was approximately twice as potent as nitrendipine (ED50 = 15 mg/kg). Wy-47,037 also reduced basal gastric acid secretion (ED50 = 7 mg/kg) and gastrointestinal motility (ED50 = 16 mg/kg). It is thus possible that Wy-47,037's alteration of basal gastric acid secretion and/or of gastrointestinal motility may contribute to its therapeutic efficacy against stress induced ulcer formation.

Restraint stress in biomedical research: a review

The use of restraint or immobilization for investigations of animal physiology, pathology and pharmacology has an extensive history. The major use of this technique has been as a "stressor" for the induction of stress response syndromes in animals. Many such syndromes have been characterized from the behavioral level to the neurochemical concomitants of stress. As a consequence of this particular use of the restraint procedure, much information concerning drug effects on stress response syndromes has been obtained. Indeed, many researchers in the area of gastrointestinal drugs routinely screen their new compounds in a restraint model of gastric stress ulcer. The purpose of this review is to present for researchers, a summary of the methods for, the parameters of, and known drug effects on, restraint-induced pathology. In our experience, this technique has proven to be a very useful one for the examination of both central and peripheral mechanisms of stress-related disorders, as well as for studying drug effects upon these disorders.

Advances in calcium blocker therapy

Calcium blockers are drugs that interfere with the entry of calcium ions into cells of a variety of tissues. Three calcium blockers, verapamil, nifedipine, and diltiazem, are currently approved for clinical use in the United States and many others are undergoing clinical trials. All calcium blockers share the effect of dilating blood vessels, although some agents are selective dilators of certain vascular beds, such as the coronary or cerebral circulation. There exist major differences among these drugs in their ability to depress myocardial contraction and inhibit cardiac impulse conduction, as well as other properties. The therapeutic actions of the agents in use, as well as the actions of the investigational calcium blockers, have been reviewed. Although calcium blockers are generally well tolerated and have fewer side effects than many alternative drugs, serious adverse effects are possible in certain clinical settings. The clinical indications for these drugs continue to expand and will likely find many uses in surgical patients, especially in the areas of cardiac surgery, neurosurgery, vascular surgery, and general surgery.