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

Protective effect of mirtazapine on indomethacin-induced ulcer in rats and its relationship with oxidant and antioxidant parameters

Even though there are many drugs for the treatment of gastric ulcers, these drugs sometimes cannot succeed. Since the 1950s, antidepressant drugs have been used for several non-psychiatric indications. A lot of antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study aimed to investigate the antiulcer effects of mirtazapine and to determine its relationship with antioxidant mechanisms. The antiulcer activities of 15, 30, and 60 mg/kg mirtazapine have been investigated on indomethacin-induced ulcers in rats, and the results have been compared with that of the control group. Mirtazapine decreased the indomethacin-induced ulcers significantly at all doses used. Mirtazapine significantly increased the glutathione (GSH) level, which decreased in the control group given only indomethacin. All doses of mirtazapine significantly decreased the catalase (CAT) level in stomach tissue compared to the control. Additionally, all doses of mirtazapine reversed the decrease in the superoxide dismutase (SOD) level in the stomach tissue of control rats. And finally, all doses of mirtazapine decreased malondialdehyde (MDA) and myeloperoxidase (MPO) levels significantly compared to the control. In conclusion, the activation of enzymatic and non-enzymatic antioxidant mechanisms and the inhibition of some toxic oxidant mechanisms play a role in the antiulcer effect mechanism of mirtazapine. This new indication of mirtazapine will make it the first-choice drug in depressive patients with gastric ulcers.

Gastroprotective and antioxidant effects of opipramol on indomethacin-induced ulcers in rats

Tricyclic antidepressants are particularly useful in the treatment of endogenous depression. Since the 1950s, tricyclic antidepressants (TCAs) have also been used for the treatment of gastric ulcer disease. Many TCAs have been evaluated for their antiulcer effects, but there are presently no data in the literature specifically concerning the antidepressant opipramol. This study aimed to investigate the antiulcer effects of opipramol and to determine its potential relationship with oxidant and antioxidant systems. The antiulcer activities of 25, 50 and 100 mg/kg opipramol have been investigated on indomethacin-induced ulcers in rats. Compared with a control group (indomethacin alone), opipramol decreased indomethacin-induced ulcers significantly at all doses used (52%, 71% and 76% respectively). Opipramol also significantly increased the glutathione (GSH), superoxide dismutase (SOD) and nitric oxide (NO) levels in the stomach tissue, all of which were decreased in the control group given only indomethacin. All doses of opipramol also significantly decreased myeloperoxidase (MPO), malondialdehyde (MDA) and catalase (CAT) levels in stomach tissue compared to the control. In conclusion, the activation of enzymatic and non-enzymatic antioxidant mechanisms, as well as the inhibition of some toxic oxidant mechanisms, appear to play a role in the antiulcer effect of opipramol. This new indication for opipramol prompts a rethinking about the possible clinical application of opipramol, particularly for peptic ulcer patients also presenting depression.

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.

Strain-dependent modification of behavior following antidepressant treatment

The effects of repeated antidepressant drug treatment on behavioral outcome in Wistar Kyoto (WKY) rats, a putative animal model of depressive behavior, were compared to Wistar and Sprague-Dawley (SD) rats. Rats were treated with desipramine (norepinephrine [NE] uptake blocker), nomifensine (NE and dopamine [DA] uptake blocker), paroxetine (serotonin [5-HT] uptake blocker) or saline, for 12 days. On Day 11, rats were tested in the Porsolt forced swim test (FST). On Day 12, rats were tested in the open field test (OFT). Stress reactivity was assessed on Day 13 when all rats were exposed to water-restraint ulcerogenic stress. Significant strain differences in behavioral responses to the drug treatments were observed. Control WKY rats showed the typical freezing behavior in the OFT and excessive floating behavior in the FST as compared to Wistar and SD rats. Desipramine and nomifensine decreased immobility and increased swim time in the FST in WKY rats. Nomifensine reduced response latency in the OFT in WKY rats and increased activity in the OFT in WKY and SD rats. None of the drugs altered the FST in SD rats. Following ulcerogenic stress, desipramine was the only antidepressant that decreased ulcer incidence in all rat strains compared to saline controls. These results suggest that the "depressive behavior" in WKY rats may be modified by antidepressants that alter synaptic levels of NE and/or DA, but not 5-HT.

Different susceptibility of stress-induced gastric ulcer and the autonomic nervous function in the hereditary hypertensive rats

Susceptibility of stress-induced ulcer by restraint water immersion (RWI) was examined in Wistar Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and stroke-prone spontaneously hypertensive rats (SHRSP). Ulcer formation was slight in SHR, and very slight in SHRSP. The ulcer index and blood pressure showed a significant inverse correlation (P < 0.001). Acid secretion was lowest in SHRSP, and hypergastrinemia was present in SHRSP. Gastric motility was suppressed during RWI in SHR and SHRSP. The noradrenaline content of the gastric mucosa and muscle layer was significantly greater in these hypertensive strains, and histologically noradrenergic innervation in the mucosa was also denser in SHRSP and SHR. Choline acetyltransferase activity in the stomach was significantly lower in SHR and SHRSP than WKY (P < 0.01). These findings suggest that susceptibility of stress-induced ulcer is inversely correlated with systemic blood pressure and that the alteration of autonomic nervous function contributes to inhibition of stress ulcers by suppressing acid secretion and motility in the hereditary hypertensive rats.

The mechanism of low susceptibility to stress in gastric lesions of spontaneously hypertensive rats

The mechanism of low susceptibility to stress in gastric lesion formation in spontaneously hypertensive rats (SHR) was investigated focusing on the sympathetic and parasympathetic nervous systems. In the gastric tissues of SHR, norepinephrine (NE) and dopamine (DA) contents were higher, while acetylcholine content and choline acetyltransferase activity were lower than those of Wistar-Kyoto rats (WKY). Water-immersion restraint induced gastric lesions frequently in WKY (ulcer indices : 52 +/- 7mm2) but less frequently in SHR (ulcer indices : 3 +/- 1mm2). Although NE content decreased in both SHR and WKY as a result of water-immersion restraint, it remained higher in SHR than in WKY. ACh content decreased by the procedure in WKY but not in SHR. DA content was increased by the procedure in all gastric regions of SHR. The gastric lesions induced in SHR were aggravated by pretreatment with 6-hydroxydopamine, an agent for chemical sympathectomy, following decreases of NE and DA contents. These results indicate that the relative sympathetic hyperfunction, parasympathetic hypofunction and dopaminergic mechanism in the stomach contribute to the prevention of gastric lesion formation in SHR.

Noradrenergic mechanisms in the central amygdalar nucleus and gastric stress ulcer formation in rats

Microinjections of noradrenaline (NA, 0.3, 3.0 and 30.0 micrograms) into the central amygdalar nucleus (CEA) produced dose-related attenuations of cold restraint (3 h at 4 degrees C) induced gastric ulcer formation in rats. On the other hand, stress ulcer aggravating effects were seen with beta-adrenoceptor antagonist, propranolol (10 micrograms) but not with the alpha-adrenoceptor antagonist, prazosin (1 and 10 micrograms). Moderate enhancements of gastric stress lesions were also seen with the NA release inhibitor clonidine (1 microgram) and the neurotoxin DSP-4 (25 micrograms). Further, pretreatment of rats with intra-amygdalar (i.am.) propranolol but not prazosin, antagonized and reversed the gastric cytoprotective effects of NA. The results indicate that beta-adrenoceptor-mediated NAergic mechanisms at the level of the CEA are important for the maintenance of gastric mucosal integrity during immobilization stress.

Imipramine prevents stress gastric glandular lesions in rats

Intraperitoneal (i.p.) administration of imipramine dose-dependently inhibited gastric lesions induced by 3 h of cold restraint stress. The high dose of imipramine (5 mg/kg) almost completely abolished gastric lesion formation, and also suppressed acid secretion in rats with pyloric ligation. Intracisternal imipramine (1 microgram) was also protective. These findings suggest that tricyclic antidepressants may play an important role in preventing the deleterious effects of stress on the gut.

Observations on dopamine receptor antagonists and gastric ulceration associated with experimental anorexia cachexia

Gastric ulceration is frequently reported to occur in tumour-bearing animals and man, even when such tumours are not associated with organs of digestion. That central and peripheral dopamine (DA) containing neurones may be relevant to this phenomenon, is supported by the fact that the DA receptor antagonists domperidone (0.1 and 0.05 mg/kg) and pimozide (0.1 mg/kg) were observed to prevent gastric ulceration commonly reported in rats bearing the Walker 256 carcinosarcoma. Daily administration of these drugs prevented the formation of ulcers similar to those observed in vehicle-treated animals. These results demonstrate that DA neurone function is important in the formation of gastric ulcers in tumour-bearing animals and suggest that such compounds may be useful in cancer management.

Influence of thyroid states on stress gastric ulcer formation

Thyroid hormones exert a critical developmental and regulatory role on the morphology and biochemistry of gastrointestinal mucosal cells. However, the relationship between thyroid function and stress gastric lesion formation remains undetermined. This study was designed to test the hypothesis that thyroid states may affect the acute development of gastric lesions induced by cold-restraint stress. Normal (euthyroid), hyperthyroid (200 micrograms of T4 i.p. x 7 days) and hypothyroid (thyroidectomized) rats were used. Gastric lesion incidence and severity was significantly (p less than 0.05) increased in hypothyroid rats, whereas in contrast hyperthyroid rats developed significantly less gastric lesions. As anticipated, plasma levels of thyroxin (T4) were significantly (p less than 0.01) elevated in hyperthyroid rats, and undetectable in hypothyroid rats. Acute pretreatment with i.p. cimetidine (100 mg/Kg), but not T4 (200 micrograms/Kg) 1 h prior to stress completely prevented gastric lesions formation in hypothyroid rats. Finally, binding of 3H-dihydroalprenolol to beta-adrenergic receptors on brain membranes prepared from frontal cortex was reduced by 20% in hypothyroid rats after 3 h of stress. These and other data contained herein suggest that thyroid hormones contribute to modulate the responsiveness of the gastric mucosa to stress. The increased rate of ulcerogenesis observed in hypothyroid rats appears to be mediated by gastric acid secretion. The central mechanism of this response may involve decreased brain nonadrenergic receptor function.

Adrenergic modulation of gastric stress pathology in rats: a cholinergic link

The effects of some adrenergic drugs were evaluated on cold restraint-induced gastric ulcers in rats. The beta-adrenergic antagonist, (+/-)-propranolol (1 and 10 mg/kg), as well as the beta-agonist, isoproterenol (0.05 and 0.5 mg/kg) potentiated the gastric pathology. On the other hand, the alpha-agonist, clonidine (0.5 mg/kg) attenuated and the alpha-antagonist, yohimbine (1 mg/kg) aggravated stress ulcer development. The anticholinergic agent, atropine methylnitrate (1 mg/kg), reduced both the frequency and severity of stress ulcers and also antagonized the potentiating effects of (+/-)-propranolol, isoproterenol and yohimbine. The results suggest a cholinergic role in the adrenergic modulation of gastric stress pathology.

The central amygdala and immobilization stress-induced gastric pathology in rats: neurotensin and dopamine

Bilateral microinjections of neurotensin (3, 10 and 30 micrograms) into the central amygdala had a dose-related attenuating effect on cold-restraint gastric ulcers in rats. Similar inhibitory effects were also observed with intra-amygdalar dopamine (3, 10 and 30 micrograms). Pretreatment with 6-hydroxydopamine (10 micrograms) or haloperidol (1 mg/kg), however, reversed the ulcer attenuating effect of neurotensin. The results indicate that the central amygdala is important in the mediation of the cytoprotective effects of neurotensin and dopamine.

Effect of hypophysectomy, adrenalectomy, pituitary hormone secretion and gastric acid secretion on neurotensin induced gastric protection against stress gastric lesions

In previous studies we have established that intracisternal (i.c.) but not peripheral (intravenous) administration of neurotensin (NT), a brain and gastrointestinal tridecapeptide, totally prevents the development of gastric lesions produced by cold-restraint stress (CRS) with food-deprived rats. In this investigation, removal of the pituitary and adrenal gland, anterior pituitary hormone secretion and gastric acid secretion were evaluated independently as potential intermediates for NT's protective effect. NT (30 micrograms) produced a significant reduction of gastric lesions incidence and severity in intact and sham-operated controls. Adrenalectomy, but not hypophysectomy totally blocked the protective effect of i.c. NT. In addition, replacement therapy with s.c. prednisone (1 mg/kg) for 5 days following adrenalectomy did not restore the protective activity of central (i.c.) NT in adrenalectomized rats. A significant reduction of serum levels of TSH, PRL and GH following i.c. NT (30 micrograms) was observed after 2h of CRS. The gastrosecretory studies revealed that i.c. NT (30 micrograms) did not affect gastric acid secretion in pylorus ligated rats. However, blockade of peripheral (gut) cholinergic (muscarinic) receptors with i.p. atropine methylbromide (1 mg/kg) significantly raised gastric pH and reduced gastric acid concentration and output. In conclusion, the results of this study indicate that the acute protective effect of brain NT appears to be mediated, at least in part, by the sympathoadrenomedullary axis, and not by the pituitary gland or substances derived from the pituitary or by inhibition of gastric acid secretion.

Neuroendocrine mechanisms of stress ulceration: focus on thyrotropin-releasing hormone (TRH)

It is generally accepted that stress ulceration, a multifactorial or pluricausal gastrointestinal disorder, may be the result of mechanistic interrelationships between mucosal, vascular, hormonal and neurogenic factors. The relative importance of each of these independent mechanisms remains unclear. This minireview represents an attempt to interpret many recent studies on certain neurogenic mechanisms and to integrate these observations into the existing body of knowledge. A variety of in vitro techniques and animal models to manipulate actual structures, organ systems, and certain well-defined hormonal influences have been utilized. The peripheral studies have followed, for the most part, the established observation that the stomach is under reciprocal control by sympathetic inhibitory and parasympathetic excitatory autonomic fibers. As a result, several autonomic adrenergic neurotransmitter substances have been found to promote mucosal resistance. Some of these include dopamine, epinephrine, and norepinephrine. Others in contrast, appear to promote vulnerability of the mucosa, and of these, the most well-studied include acetylcholine and histamine.

Methylphenidate effects on activity-stress gastric lesions and regional brain noradrenaline metabolism in rats

Methylphenidate (5, 10, or 20 mg/kg/day) or saline were administered to rats in the activity-stress ulcer paradigm. Running-wheel activity and food consumption did not differ among groups. Methylphenidate produced dose-related increases in gastric ulcer severity, decreases in hypothalamic noradrenaline (NA) and increases in 3-methoxy-4-hydroxy-phenylethyleneglycol sulfate (MHPG-SO4) in the hypothalamus, amygdala, hippocampus and thalamus. These results differ markedly from the effects seen with a related substance, d-amphetamine, and suggest different mechanisms of action for these drugs.