Role of local motility changes in the pathogenesis of duodenal ulcers induced by cysteamine in rats

Effects of Cistus laurifolius L. flowers on gastric and duodenal lesions

The flowers and flower buds of Cistus laurifolius L. are used for the treatment of peptic ulcers. Through the bioassay-guided fractionation of the material, using water immersion and immobilisation-induced stress ulcer model, the EtOH-precipitated part from the aqueous extract (E-H2O decreases) was determined to be the active fraction. For the evaluation of the mode of action, the activity of E-H2O decreases was tested using various ulcer models in rats and mice and this fraction was found active against pylorus ligation-, abs. ethanol-, indomethacin-, indomethacin plus HCl/EtOH-induced gastric and cysteamine-induced duodenal lesions while ineffective against serotonin-induced gastric lesions. The active fraction showed its activity not only on per os administration but also after subcutanous injection. According to the results of biochemical studies, the active fraction showed a potent antiacid activity. In addition, histopathological, and toxicological studies were conducted with the active fraction.

Gastric and duodenal anti-ulcer activity of sulpiride, a dopamine D2 receptor antagonist, in rats

The gastric and duodenal anti-ulcer activity of sulpiride, a dopamine D2 receptor antagonist, was studied on various types of experimentally induced ulcers in rats, viz., pylorus ligation and water immersion + restraint stress-induced gastric ulcers, gastric mucosal damage induced by nonsteroidal anti-inflammatory drugs and reserpine, and duodenal ulcers induced by cysteamine hydrochloride. It has been found to possess significant anti-ulcer activity against all these models. In 19 h pylorus ligated rats, it significantly reduced the gastric secretion, increased the fucose and sialic acid concentration of the gastric juice and reduced its protein content, thus increasing the total carbohydrate:protein (TC/PR) ratio. These results suggest that the antisecretory and gastric mucosal barrier strengthening effects of sulpiride may be responsible for its anti-ulcer activity. A central component also appears to be involved in its anti-ulcer action against water immersion + restraint stress model. The results of this study provide a rationale for its beneficial effect seen in the therapy of peptic ulcer disease.

Effects of compound U74500A in animal models of gastric and duodenal ulceration

Pretreatment with U74500A (up to 0.65 mg/100 g) failed to affect gastric lesions induced by 100% EtOH gavage in Sprague-Dawley rats. Topical application of U74500A did not reduce lesions induced by 40% EtOH in ex vivo gastric chamber preparations. However, pretreatment of rats with U74500A (0.65 g/100 g per os) reduced the incidence and severity of experimental duodenal ulcer induced by cysteamine HCl, and duodenal ulcer induced by cysteamine-HCl plus GABA. These results show U74500A to have powerful and specific antiduodenal ulcer actions. Pharmacologic analysis of organ-bath preparations of the small intestine show this compound to reduce intestinal contractility to applied cholinergic and serotonergic agonists. However, relaxations induced by electrical or nicotinic ganglionic stimulation were unaffected. U74500A itself caused concentration-dependent contractions.

Disturbed gastroduodenal motility in patients with active and healed duodenal ulceration

Disordered gastroduodenal motility may promote duodenal ulceration by allowing prolonged acid contact with the duodenal mucosa. Using a multilumen perfused catheter incorporating 3 pH microelectrodes, antral and duodenal pH and antropyloroduodenal pressure activity were recorded in 36 subjects (10 with healed duodenal ulceration, 11 with active duodenal ulceration, and 15 healthy volunteers) during fasting and after a radiolabeled solid test meal. Correct pH probe/catheter position was continuously verified by recording transmucosal potential difference across the pylorus. Patients with active and healed duodenal ulcer had similarly disordered gastroduodenal motility. The chief abnormalities consisted of an increase in postprandial duodenal retroperistalsis (healed duodenal ulceration, 12 +/- 1 events per hour; active duodenal ulceration, 12 +/- 1; control, 6 +/- 1; mean +/- SEM: healed and active duodenal ulceration vs. control, P = 0.004 and P = 0.03, respectively), a reduction in pressure waves sweeping aborally through the duodenum after the meal (healed duodenal ulceration, 22 +/- 4 events per hour; active duodenal ulceration, 23 +/- 3; control, 34 +/- 4: healed and active duodenal ulceration vs. control, P = 0.04 and P less than 0.05, respectively), and an increased incidence of atypical, complex forms of coordinated duodenal motor activity throughout the study (postprandial data; healed duodenal ulceration, 8 +/- 1 events per hour; active duodenal ulceration, 10 +/- 1; control, 4 +/- 1: healed and active duodenal ulceration vs. control, P = 0.02 and P less than 0.02, respectively). In addition, gastric emptying of the solid test meal was significantly delayed in healed, but not active, duodenal ulceration [half-emptying time, healed duodenal ulceration 185 minutes (117-235); active duodenal ulceration 102 minutes (80-200); control 107 minutes (78-130): healed duodenal ulceration vs. control, P less than 0.009]. Duodenal bulb pH was similar in controls and patients with active duodenal ulceration; however, bulb pH was less than 4 for a significantly greater period of time in healed duodenal ulceration compared with active ulcer patients, particularly after the meal. In conclusion, duodenal ulcer disease is associated with disturbed gastroduodenal motility, even when the ulcer is quiescent and when intraduodenal acidity is low. In healed duodenal ulceration, disturbed motility may promote ulcer relapse by impairing acid clearance from the bulb. However, in active ulceration other factors such as mucosal bicarbonate secretion may have a more influential role in determining intraduodenal pH.

Ulcers produced by ligation of individual gastric mucosal arteries in the guinea pig

It is not known whether or not individual gastric mucosal arteries are end-arteries. We therefore occluded single mucosal guinea pig arteries, resulting in necrosis of the whole thickness of mucosa in the area supplied by the artery in 25 of 33 cases (76%). However, there were no cases of necrosis in 33 control sham ligations performed in the same animals (p less than 0.001). In another group, ligation of two or three adjacent mucosal arteries resulted in necrosis in 10 of 11 cases (p less than 0.0001), against 0 necrosis in 11 sham ligations. Killing the animals at varying intervals showed that after 1 day the mucosa was necrotic, after 2 days it was shed, and later it might perforate. We conclude that many mucosal arteries in the guinea pig may behave as functional end-arteries. How these findings may pertain to ulceration is discussed in relation to (a) the existence of atypical mucosal arteries found in the ulcer-bearing areas in humans and (b) the role of the muscularis mucosae on arterioles perforating it in both humans and other species.

Augmentation of cysteamine-induced ulceration of rat duodenum by systemically administered gamma-aminobutyric acid (GABA)

Subcutaneous administration of a single dose of gamma-aminobutyric acid (GABA, 10 mg/100 g) in conjunction with a pretreatment dose of aminooxyacetic acid (AOAA 2.5 mg/100 g subcutaneously) to prevent the degradation of GABA, significantly augmented the incidence and intensity of cysteamine HCl-induced duodenal ulceration in rats. This effect of GABA could be reduced by the GABA receptor antagonist, bicuculline (30 micrograms/100 g subcutaneously). These results suggest peripheral GABA receptors can modulate cysteamine HCl-induced duodenal ulcer.

Interactions of the ulcerogen cysteamine with enteric inhibitory nerves and putative transmitters in the rat small intestine

1. The effects of the ulcerogen cysteamine (2-aminoethanethiol HCL) on spontaneous activity and evoked responses of rat isolated small intestine preparations were investigated in vitro. 2. Cysteamine induced concentration-dependent relaxations of isolated segments of the rat duodenum, jejunum and ileum. These actions were manifest simultaneously in both the circular and longitudinal muscle layers, where the responses displayed a similar profile. 3. Treatment with tetrodotoxin (0.1 microM) or cold storage of individual preparations to prevent nerve-mediated responses abolished the effects of cysteamine. The presence of atropine (0.1 microM), propranolol (3.0 microM) and phentolamine (3.0 microM) in the bathing solution did not affect the cysteamine-evoked relaxations, suggesting cysteamine was stimulating non-adrenergic, non-cholinergic (NANC) intrinsic inhibitory nerves. 4. Applied cysteamine reversibly reduced GABA- and DMPP-evoked NANC nerve-mediated relaxations via actions unrelated to the receptors for these agents. 5. Methysergide-sensitive (direct) actions of 5-HT on the muscularis but not 5-HT neurally evoked responses were blocked by cysteamine. 6. It would appear that cysteamine has excitatory and inhibitory actions on enteric inhibitory nerves as well as specifically interfering with myogenic but not neural actions of 5-HT.

Effect of duodenal ulcerogens cysteamine, mepirizole, and MPTP on duodenal myoelectric activity in rats

Increased gastric acid secretion, enhanced acid delivery to the duodenum, and reduced alkaline secretion in the proximal duodenum are relatively well-established pathophysiologic abnormalities in duodenal ulcer. Impaired duodenal motility, however, may also contribute to duodenal ulceration by altering the distribution of acid and alkaline secretions along the upper digestive tract. We tested the hypothesis that the duodenal ulcerogens cysteamine, MPTP, and mepirizole modify duodenal motility in the rat and that motility changes might be a common and early alteration in experimental duodenal ulceration. All three duodenal ulcerogens rapidly produced extensive changes in duodenal myoelectric activity and reduced the frequency of myoelectric slow waves. Cysteamine induced marked hypermotility for at least 6 hr; MPTP rapidly decreased motility and fragmented the myoelectric migrating pattern. Mepirizole induced biphasic changes: an early hypermotility phase of about 30 min was followed by profound hypomotility. These results indicate that marked alterations of duodenal motility are common during experimental duodenal ulceration. In light of the differential effect of the ulcerogens on duodenal motility, it remains to be determined how these changes influence acid neutralization in the proximal duodenum. Nevertheless, our results suggest that all three duodenal ulcerogens, which are different in structure, alter duodenal motility.

Effects of dopamine on gastric mucosal lesions induced by ethanol in rats. Possible involvement of antigastric motor activity mediated with alpha 2-adrenoceptors

Acidified ethanol (60% ethanol in 150 mM HCl, per os) induced elongated bands of hemorrhagic lesions along the long axis of the stomach within 1 hr in rats. Pretreatment with dopamine hydrochloride (DA: 1-10 mg/kg, subcutaneously) dose-dependently reduced the severity of these lesions. In parallel study, DA had no effect on acid secretion but inhibited gastric motor activity in a dose-related manner. The inhibitory effects of DA on both acidified ethanol-induced lesions and gastric motor activity were significantly reversed by pretreatment with yohimbine, an inhibitor of alpha 2-adrenoceptors (5 mg/kg, subcutaneously), but not by prazosin, haloperidol, or indomethacin. Similar to DA, both norepinephrine (NE: 1 mg/kg, subcutaneously) and epinephrine (EPI: 1 mg/kg, subcutaneously) showed inhibition of the motor activity and gastroprotection against acidified ethanol, but these effects were also significantly attenuated by yohimbine. A highly significant relationship was found between the inhibitory effects of DA, NE, and EPI on the motor activity and the mucosal lesions (r = 0.8577, P less than 0.05). In addition, administration of gentian violet (0.5% w/v, per os) stained the mucosa deep blue as elongated wide bands in the corpus region, and such localized staining was significantly prevented by DA, suggesting a flattening of the mucosal foldings in the presence of DA. These results suggest that DA (and other catecholamines) protects the rat gastric mucosa against injury caused by acidified ethanol, probably through inhibition of gastric motor activity mediated with stimulation of alpha 2-adrenoceptors.