Investigation on the mechanism involved in the effects of agmatine on ethanol-induced gastric mucosal injury in rats

Gastroprotective and antioxidant effects of fluvoxamine on stress-induced peptic ulcer in rats

Objectives

Stress-induced peptic ulcer disease (SPUD) refers to erosions in the mucosa of the upper gastrointestinal tract that are caused by stress. Some antidepressants are reported to have antioxidant and antiulcer effects. However, histopathological and biochemical evaluation of the anti-ulcer activity of a comparable antidepressant, fluvoxamine, has not been adequately investigated. This study aims to determine the anti-ulcer efficacy of fluvoxamine in reducing stress-induced histopathological and biochemical changes in the gastric mucosa.

Methods

Thirty adult male albino rats were divided into three groups of 10 rats each: the control groups, the SPUD group, and the fluvoxamine-pre-treated group, which received fluvoxamine for eight days before stress exposure. The cold-restraint stress method was used to induce stomach ulcers in the SPUD and fluvoxamine groups. Afterward, the stomachs of rats were removed, opened, and ulcer indices were calculated. Light microscopy was performed following haematoxylin and eosin staining, periodic acid Schiff's, Masson's trichrome staining, and proliferating cell nuclear antigen immunostaining. Gastric tissue levels of oxidative stress markers were measured and compared among groups.

Results

The stomachs of the fluvoxamine-treated rats showed a significantly lower number of ulcers with minimal mucosal injury compared with those of rats from the SPUD group. The oxidative stress marker levels and SPUD ulcer indices were significantly different among groups.

Conclusion

Fluvoxamine pre-treatment exerted a gastroprotective effect against ulcer development and promoted healing of the developed lesions.

Agmatine induces gastric protection against ischemic injury by reducing vascular permeability in rats

AIM: To investigate the effect of administration of agmatine (AGM) on gastric protection against ischemia reperfusion (I/R) injury.

METHODS: Three groups of rats (6/group); sham, gastric I/R injury, and gastric I/R + AGM (100 mg/kg, i.p. given 15 min prior to gastric ischemia) were recruited. Gastric injury was conducted by ligating celiac artery for 30 min and reperfusion for another 30 min. Gastric tissues were histologically studied and immunostained with angiopoietin 1 (Ang-1) and Ang-2. Vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1) were measured in gastric tissue homogenate. To assess whether AKt/phosphatidyl inositol-3-kinase (PI3K) mediated the effect of AGM, an additional group was pretreated with Wortmannin (WM) (inhibitor of Akt/PI3K, 15 μg/kg, i.p.), prior to ischemic injury and AGM treatment, and examined histologically and immunostained. Another set of experiments was run to study vascular permeability of the stomach using Evan’s blue dye.

RESULTS: AGM markedly reduced Evan’s blue dye extravasation (3.58 ± 0.975 μg/stomach vs 1.175 ± 0.374 μg/stomach, P < 0.05), VEGF (36.87 ± 2.71 pg/100 mg protein vs 48.4 ± 6.53 pg/100 mg protein, P < 0.05) and MCP-1 tissue level (29.5 ± 7 pg/100 mg protein vs 41.17 ± 10.4 pg/100 mg protein, P < 0.01). It preserved gastric histology and reduced congestion. Ang-1 and Ang-2 immunostaining were reduced in stomach sections of AGM-treated animals. The administration of WM abolished the protective effects of AGM and extensive hemorrhage and ulcerations were seen.

CONCLUSION: AGM protects the stomach against I/R injury by reducing vascular permeability and inflammation. This protection is possibly mediated by Akt/PI3K.

Agmatine, an endogenous imidazoline receptor ligand modulates ethanol anxiolysis and withdrawal anxiety in rats

Present study investigated the role of agmatine in ethanol-induced anxiolysis and withdrawal anxiety using elevated plus maze (EPM) test in rats. The anxiolytic-like effect of ethanol was potentiated by pretreatment with imidazoline I(1)/I(2) receptor agonist agmatine (10-20 mg/kg, i.p.), imidazoline I(1) receptor agonists, moxonidine (0.25 mg/kg, i.p.) and clonidine (0.015 mg/kg, i.p.), imidazoline I(2) receptor agonist, 2-BFI (5 mg/kg, i.p.) as well as by the drugs known to increase endogenous agmatine levels in brain viz., L-arginine, an agmatine biosynthetic precursor (100 microg/rat, i.c.v.), ornithine decarboxylase inhibitor, DFMO (125 microg/rat, i.c.v.), diamine oxidase inhibitor, aminoguanidine (65 microg/rat, i.c.v.) and agmatinase inhibitor, arcaine (50 microg/rat, i.c.v.). Conversely, prior administration of I(1) receptor antagonist, efaroxan (1 mg/kg, i.p.), I(2) receptor antagonist, idazoxan (0.25mg/kg, i.p.) and arginine decarboxylase inhibitor, D-arginine (100 microg/rat, i.c.v.) blocked the anxiolytic-like effect of ethanol. Moreover, ethanol withdrawal anxiety was markedly attenuated by agmatine (10-20 mg/kg, i.p.), moxonidine (0.25 mg/kg, i.p.), clonidine (0.015 mg/kg, i.p.), 2-BFI (5 mg/kg, i.p.), L-arginine (100 microg/rat, i.c.v.), DFMO (125 microg/rat, i.c.v.), aminoguanidine (65 microg/rat, i.c.v.) and arcaine (50 microg/rat, i.c.v.). The anti-anxiety effect of agmatine in ethanol-withdrawn rats was completely blocked by efaroxan (1 mg/kg, i.p.) and idazoxan (0.25 mg/kg, i.p.). These results suggest that agmatine and imidazoline receptor system may be implicated in ethanol-induced anxiolysis and withdrawal anxiety and strongly support further investigation of agmatine in ethanol dependence mechanism. The data also project agmatine as a potential therapeutic target in overcoming alcohol withdrawal symptoms such as anxiety.

Antiulcer activity of fluvoxamine in rats and its effect on oxidant and antioxidant parameters in stomach tissue

Background

Although many drugs are available for the treatment of gastric ulcers, often these drugs are ineffective. Many antidepressant drugs have been shown to have antiulcer activity in various models of experimental ulcer. One such drug, the antidepressant mirtazapine, has been reported to have an antiulcer effect that involves an increase in antioxidant, and a decrease in oxidant, parameters. To date, however, there is no information available regarding the antiulcer activity for a similar antidepressant, fluvoxamine. This study aimed to investigate the antiulcer effects of fluvoxamine and to determine its relationship with antioxidants.

Methods

Groups of rats fasted for 24 h received fluvoxamine (25, 50, 100 and 200 mg/kg), ranitidine (50 mg/kg) or distilled water by oral gavage. Indomethacin (25 mg/kg) was orally administered to the rats as an ulcerative agent. Six hours after ulcer induction, the stomachs of the rats were excised and an ulcer index determined. Separate groups of rats were treated with the same doses of fluvoxamine and ranitidine, but not with indomethacin, to test effects of these drugs alone on biochemical parameters. The stomachs were evaluated biochemically to determine oxidant and antioxidant parameters. We used one-way ANOVA and least significant difference (LSD) options for data analysis.

Results

The 25, 50, 100 and 200 mg/kg doses of fluvoxamine exerted antiulcer effects of 48.5, 67.5, 82.1 and 96.1%, respectively, compared to the control rat group. Ranitidine showed an 86.5% antiulcer effect. No differences were observed in the absence of indomethacin treatment for any dose of fluvoxamine or for ranitidine. The levels of antioxidant parameters, total glutathione and nitric oxide, were increased in all fluvoxamine groups and in the ranitidine group when compared with the indomethacin-only group. In addition, fluvoxamine and ranitidine decreased the levels of the oxidant parameters, myeloperoxidase and malondialdeyhyde, in the stomach tissues of the rats when compared to indomethacin group.

Conclusion

We conclude that fluvoxamine has antiulcer effects, and that these occur by a mechanism that involves activation of antioxidant parameters and inhibition of some toxic oxidant parameters.

Comparative study on the gastroprotective potential of some antidepressants in indomethacin-induced ulcer in rats

Clinical studies have shown that anxiolytic and antidepressant drug therapy benefits patients with ulcers. Many antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study investigated the antiulcer activities of tianeptine, trazodone, and venlafaxine on indomethacin-induced ulcers in rats; and evaluated tianeptine's effects on oxidant and antioxidant parameters in rat stomach tissue. The results show that trazodone and venlafaxine did not prevent indomethacin-induced ulcers. Tianeptine, however, decreased indomethacin-induced ulcers significantly at all doses used (6, 12, and 25 mg/kg). Famotidine, an H(2) receptor blocker, showed the highest antiulcer activity. Tianeptine significantly prevented the decrease in glutathione (GSH) content that occurred in the indomethacin-only group's damaged stomach tissues. All doses of tianeptine, but especially the 25 mg/kg dose, significantly decreased catalase (CAT) activity in stomach tissue, compared to the control. All doses of tianeptine eliminated the decrease in superoxide dismutase (SOD) activity in the stomach tissue of rats given indomethacin. Although all doses of tianeptine significantly decreased the malondialdehyde (MDA) content, all doses of tianeptine, except 6 mg/kg, decreased myeloperoxidase (MPO) activities significantly compared to the control. Our results indicate that activating enzymatic and non-enzymatic antioxidant mechanisms and inhibiting some toxic oxidant mechanisms play a role in tianeptine's antiulcer effect mechanism.

Involvement of alpha(2)-adrenoceptors in the gastric protective effect of nitroglycerin against acidified ethanol-induced mucosal injury

Clinical observations reveal that alcohol intake is associated with an increase in upper gastrointestinal hemorrhage requiring hospitalization and that nitroglycerin or long-acting nitrates lower this risk. Nitroglycerin, a gastric vasodilator that can increase gastric fluid volume, protects the rodent stomach against damage, including that caused by 70% ethanol. Blockade of alpha(2)-adrenoceoptors attenuates gastric protection by intragastric nicotine against 40% ethanol. We tested the hypothesis that the protective effect of nitroglycerin is mediated by an increase in gastric fluid volume and alpha(2)-adrenoceoptors. Nitroglycerin, 5 mg/kg, vehicle, or acidified ethanol was administered intragastrically. In study 1 acidified ethanol-induced mucosal injury was measured. In study 2 the effect of increasing gastric volume (1 ml/kg) on mucosal injury was assessed. In study 3 the effect of yohimbine (alpha(2)-adrenoceoptor antagonist), 5 mg/kg subcutaneously, on the nitroglycerein-mediated protective effect was determined. Results showed that nitroglycerin significantly attenuated the number and length of mucosal lesions induced by acidified ethanol. Increase in gastric fluid volume by exogenously administered saline did not alter the protective effect. Yohimbine blocked the nitroglycerin-mediated protection. These experimental data are consistent with the observation that nitrates lower the risk of ethanol-induced gastrointestinal complications. alpha(2)-Adrenoceoptors are responsible in part for the protective effect of nitroglycerin.

Agmatine potentiates morphine-induced conditioned place preference in mice: modulation by alpha2-adrenoceptors

The effects of agmatine, an endogenous polyamine metabolite formed by decarboxylation of L-arginine, and its combination with morphine on conditioned place preference (CPP) has been investigated in male mice. Our data show that subcutaneous administration of morphine (1-7.5 mg/kg) significantly increases the time spent in the drug-paired compartment in a dose-dependent manner. Intraperitoneal administration of agmatine (1-40 mg/kg) alone does not induce either CPP or conditioned place aversion, while combination of agmatine and subeffective doses of morphine leads to potent rewarding effects. Lower doses of morphine (0.1, 0.05, and 0.01 mg/kg) are able to induce CPP in mice pretreated with agmatine 1, 5, and 10 mg/kg, respectively. Concomitant intraperitoneal administration of UK 14 304 (0.5 mg/kg), a highly selective alpha2-agonist, with per se noneffective dose of morphine (0.5 mg/kg) and also its combination with noneffective doses of agmatine (1 mg/kg) plus morphine (0.05 mg/kg) produces significant CPP. UK 14 304 (0.05, 0.5 mg/kg) alone, or in combination with agmatine (1, 5 mg/kg) have had no effect. We have further investigated the possible involvement of the alpha2-adrenoceptors in the potentiating effect of agmatine on morphine-induced place preference. Selective alpha2-antagonists, yohimbine (0.005 mg/kg) and RX821002 (0.1, 0.5 mg/kg), block the CPP induced by concomitant administration of agmatine (5 mg/kg) and morphine (0.05 mg/kg). Yohimbine (0.001-0.05 mg/kg) or RX821002 (0.05-0.5 mg/kg) alone or in combination with morphine (0.05 mg/kg) or agmatine (5 mg/kg) fail to show any significant place preference or aversion. Our results indicate that pretreatment of animals with agmatine enhances the rewarding properties of morphine via a mechanism which may involve alpha2-adrenergic receptors.