The neurobiology of stress ulcers

Social and natural environmental factors cause the birth-cohort phenomenon of peptic ulcers by superposition mechanism

The widely believed Helicobacter pylori infection has never explained the birth-cohort phenomenon of peptic ulcers. Although numerous studies have observed that environmental factors are associated with peptic ulcers, their role in the disease has yet to be identified. A new etiological theory proposed that environmental factors cause peptic ulcers via inducing psychological stress. Starting from this etiology, an integration of the mortality rates caused by social and natural environmental factors reproduced a representative fluctuation curve in the birth-cohort phenomenon, where a causal role of environmental factors in peptic ulcers was hidden. The reproduced fluctuation curve revealed that multiple environmental factors caused the birth-cohort phenomenon by Superposition Mechanism, and the causal role of each individual environmental factor surfaced if the fluctuation curves in the birth-cohort phenomenon were properly differentiated. A full understanding of the birth-cohort phenomenon highlights the importance of environmental management in improving clinical outcomes, and suggests that the Superposition Mechanism is an indispensable methodological concept for life science and medicine.

New studies with stable gastric pentadecapeptide protecting gastrointestinal tract. significance of counteraction of vascular and multiorgan failure of occlusion/occlusion-like syndrome in cytoprotection/organoprotection

Since the early 1990s, when Robert's and Szabo's cytoprotection concept had already been more than one decade old, but still not implemented in therapy, we suggest the stable gastric pentadecapeptide BPC 157 as the most relevant mediator of the cytoprotection concept. Consequently, it can translate stomach and gastrointestinal mucosal maintenance, epithelium, and endothelium cell protection to the therapy of other tissue healing (organoprotection), easily applicable, as native and stable in human gastric juice for more than 24 h. These overwhelm current clinical evidence (i.e., ulcerative colitis, phase II, no side effects, and no lethal dose (LD1) in toxicology studies), as BPC 157 therapy effectively combined various tissue healing and lesions counteraction. BPC 157 cytoprotection relevance and vascular recovery, activation of collateral pathways, membrane stabilizer, eye therapy, wound healing capability, brain-gut and gut-brain functioning, tumor cachexia counteraction, muscle, tendon, ligament, and bone disturbances counteraction, and the heart disturbances, myocardial infarction, heart failure, pulmonary hypertension, arrhythmias, and thrombosis counteraction appeared in the recent reviews. Here, as concept resolution, we review the counteraction of advanced Virchow triad circumstances by activation of the collateral rescuing pathways, depending on injury, activated azygos vein direct blood flow delivery, to counteract occlusion/occlusion-like syndromes starting with the context of alcohol-stomach lesions. Counteraction of major vessel failure (congested inferior caval vein and superior mesenteric vein, collapsed azygos vein, collapsed abdominal aorta) includes counteraction of the brain (intracerebral and intraventricular hemorrhage), heart (congestion, severe arrhythmias), lung (hemorrhage), and congestion and lesions in the liver, kidney, and gastrointestinal tract, intracranial (superior sagittal sinus), portal and caval hypertension, aortal hypotension, and thrombosis, peripherally and centrally.

Effects of NO modulators and antioxidants on endocrine and cellular markers in rats under repetitive restraint stress

The aim of the study was to evaluate the effects of NO modulators and antioxidant treatments on endocrine (plasma corticosterone), cellular (heat shock protein 70 [HSP-70] and nuclear factor κB [NF-κB]), and oxidative stress markers in repetitively stressed rats. Repetitive (restraint) stress (RS 1hr/day × 21 days) enhanced the levels of cellular and endocrine stress markers in the rat blood and altered pro-oxidant-antioxidant balance differentially in the control and test groups. Exposure to repetitive RS enhanced malondialdehyde (MDA) levels, lowered reduced glutathione (GSH), and superoxide dismutase (SOD) levels as well as nitric oxide (NOx) levels. NO precursor L-arginine and NO synthase inhibitors were found to differentially modulate stress-induced mechanism in altering NF-κB, HSP-70, and corticosterone levels. The antioxidant L-ascorbic acid (L-AA) significantly suppressed RS(×21)-induced elevation of NF-κB and HSP-70 levels, depicting protective effects, as also evidenced by reversal of elevated corticosterone levels. The results suggest that NO modulators and antioxidants differentially influence repetitive stress-induced changes in endocrine and cellular markers, and the complex interaction between NO and cellular markers like HSP70 and NF-κB plays a crucial modulatory role in this phenomenon.

Cytoprotective gastric pentadecapeptide BPC 157 resolves major vessel occlusion disturbances, ischemia-reperfusion injury following Pringle maneuver, and Budd-Chiari syndrome

The stable gastric pentadecapeptide BPC 157 counteracts various venous occlusion-induced syndromes. Summarized are all these arguments, in the Robert’s cytoprotection concept, to substantiate the resolution of different major vessel occlusion disturbances, in particular ischemia-reperfusion injury following the Pringle maneuver and Budd-Chiari syndrome, which was obtained by BPC 157 therapy. Conceptually, there is a new point, namely, endothelium maintenance to epithelium maintenance (the recruitment of collateral blood vessels to compensate for vessel occlusion and reestablish blood flow or bypass the occluded or ruptured vessel). In this paper, we summarize the evidence of the native cytoprotective gastric pentadecapeptide BPC 157, which is stable in the human gastric juice, is a membrane stabilizer and counteracts gut-leaky syndrome. As a particular target, it is distinctive from the standard peptide growth factors, involving particular molecular pathways and controlling VEGF and NO pathways. In the early 1990s, BPC 157 appeared as a late outbreak of the Robert’s and Szabo’s cytoprotection-organoprotection concept, like the previous theoretical/practical breakthrough in the 1980s and the brain-gut axis and gut-brain axis. As the time went on, with its reported effects, it is likely most useful theory practical implementation and justification. Meantime, several reviews suggest that BPC 157, which does not have a lethal dose, has profound cytoprotective activity, used to be demonstrated in ulcerative colitis and multiple sclerosis trials. Likely, it may bring the theory to practical application, starting with the initial argument, no degradation in human gastric juice for more than 24 h, and thereby, the therapeutic effectiveness (including via a therapeutic per-oral regimen) and pleiotropic beneficial effects.

A collection of the etiological theories, characteristics, and observations/phenomena of peptic ulcers in existing data

In this article, we compiled 13 etiological theories, 15 characteristics, and 81 observations/phenomena of peptic ulcers, reported in reproducible, peer-reviewed studies from the literature, to reflect the historical evolution of studies on peptic ulcers and to provide a multidisciplinary view of this disease. This data was collected during the systematic review of topics on peptic ulcers including genetics, etiology, epidemiology, psychology, anatomy, neurology, bacteriology, pathology, and clinical statistics. The data curated herein was extracted via application of recently published basic theories and methodologies.

Effects of Eleutherococcus senticosus Cortex on Recovery from the Forced Swimming Test and Fatty Acid β-Oxidation in the Liver and Skeletal Muscle of mice

OBJECTIVE

The root and stem barks of Eleutherococcus senticosus have been used to treat emotional and physical fatigue in China, Russia, Korea, and Japan. The effects of E. senticosus on recovery from physical fatigue and the expenditure of energy currently remain unclear. We herein examined the effects of E. senticosus extract on recovery from physical fatigue after the forced swimming test as well as fatty acid β-oxidation in the liver and skeletal muscle of mice.

METHODS

1) Physical fatigue; E. senticosus extract (500 and 1000 mg/kg, twice daily) was administered orally to ICR male mice for 7 consecutive days. After swimming had been performed for 15 min, each mouse was placed on the cover of a 100-mm culture plate, and the time for each mouse to move away from the cover was measured. 2) Fatty acid β-oxidation in the liver and skeletal muscle; E. senticosus extract (500 and 1000 mg/kg) was administered orally twice daily to C57BL/6J male mice for 21 consecutive days. The initial and final body and liver weight were measured, and then fatty acid β-oxidation activity in the liver and skeletal muscle was measured by methods using [1-14C] palmitic acid.

KEY FINDINGS

Recovery times after forced swimming were shorter in E. senticosus extract (500 and 1000 mg/kg)-treated mice than in vehicle-treated mice. The body and liver weight had no effect by the oral administration of E. senticosus extract, vitamin mixture and L-carnitine. Fatty acid β-oxidation activity in skeletal muscle was increased by E. senticosus extract (500 and 1000 mg/kg).

CONCLUSION

E. senticosus may enhance recovery from physical fatigue induced by forced swimming by accelerating energy changes through fatty acid β-oxidation in skeletal muscle.

Participation of NMDA receptors in the lateral hypothalamus in gastric erosion induced by cold-water restraint

The present study investigated whether neurons in the lateral hypothalamus (LH) play a role in the occurrence of gastric ulcerations induced by cold-water restraint. The first experiment indicated that bilateral N-methyl-d-aspartate (NMDA) lesions of the LH (20μg/1μl per side) reduced the amount of gastric ulceration induced by cold-water restraint. In the second experiment, the NMDA antagonist DL-2-amino-5-phosphonovaleric acid (APV; 2.5μg/0.5μl per side) or its vehicle was microinjected bilaterally into the LH prior to the cold-water restraint procedure. APV did not induce gastric ulcerations but reduced the amount of ulceration induced by cold-water restraint. These results indicate that NMDA receptors in the LH play an important role in the occurrence of gastric ulceration induced by cold-water restraint. The participation of the LH and possible neuronal circuitry involved in stress-induced ulceration are discussed.

Restoring psychology's role in peptic ulcer

This paper reviews the history of the transition from the belief that gastrointestinal ulcers are caused primarily by psychological factors to the current state of belief that they are caused primarily by infection and argues that neither is fully accurate. We argue that psychological factors play a significant role as predisposing to vulnerability, modulating of precipitation, and sustaining of gastric ulceration. We review data that challenge the assumption of a simple infectious disease model and adduce recent preclinical data that confirm the predisposing, modulatory, and sustaining roles for psychological factors. We note that others, too, are now challenging the adequacy of the contemporary simple bacterial infection model. We hope to replace the competition between psychology and medicine with cooperation in understanding and treating patients suffering gastric ulceration and ulcer.

Nardostachys jatamansi extract prevents chronic restraint stress-induced learning and memory deficits in a radial arm maze task

Nardostachys jatamansi is traditionally used in alternative medicine for treatment of neuropsychiatric disorders. We investigated the potential of N. jatamansi extract (NJE) in protecting against chronic stress-induced impairments in spatial learning and memory. The rats were exposed to 21 days of chronic restraint stress and simultaneously received 100 mg or 200 mg/kg body weight of NJE following which acquisition and retention of hippocampus-dependent spatial memory were tested in a partially-baited eight arm radial maze. Animals treated with 200 mg/kg body weight NJE had learning curves comparable to control unstressed animals, made significantly more correct choices (38%, P < 0.001), and fewer reference memory errors (53%, P < 0.01) on the eighth day of training compared to untreated stressed animals as well as stressed animals which received vehicle or a lower dose (100 mg/kg) of NJE. NJE-treated animals also made significantly higher correct choices (31%, P < 0.001) than untreated animals in a retention test 10 days after the training period. We propose that NJE has a protective effect of stress-induced impairments in hippocampus-dependent learning and memory behavior in rats.

Antistress activity of Argyreia speciosa roots in experimental animals

The antistress effect of a seven-day treatment (100 and 200 mg / kg, p.o.) of the hydroalcoholic extract of Argyreia speciosa root (ASE) was evaluated by using the swimming endurance test, acetic acid-induced writhing test, pentylenetetrazole-induced convulsion test, anoxic tolerance test, cold-restraint, stress-induced gastric ulcers, aspirin-induced ulcers, and biochemical, and histopathological changes in the cold-restraint stress test. The immunomodulatory activity was also evaluated for the same doses, and treatment of ASE was done using the hemagglutination test. Both the doses of ASE showed antistress activity in all the tested models. The ASE-treated animals showed a decrease in immobility time and an increase in anoxic tolerance time in swimming endurance and the anoxic tolerance tests, respectively. The effect of glacial acetic acid and pentylenetetrazole were also reduced by decreasing the number of writhing responses and increasing the onset of convulsions, respectively. In the cold restrained stress and aspirin-induced gastric ulcer models, ASE showed a significant reduction in the ulcer index. Pretreatment with ASE significantly ameliorated the cold stress-induced variations in biochemical levels such as increased plasma cholesterol, triglyceride, glucose, total protein, and cortisol. ASE was also effective in preventing the pathological changes in the adrenal gland, due to cold restrained stress, in rats. In mice immunized with sheep red blood cells, the treatment groups subjected to restraint stress prevented the humoral immune response to the antigen. The immunostimulating activity of the ASE was indicated by an increase in the antibody titer in mice pre-immunized with sheep red blood cells and subjected to restraint stress. The findings of the present investigations indicate that the ASE has significant antistress activity, which may be due to the immunostimulating property and increased resistance, nonspecifically, against all experimental stress conditions.

Glabridin from Chinese herb licorice inhibits fatigue in mice

The inhibiting effect of glabridin from Chinese herb Licorice on fatigue was investigated in male BALB/c mice. Mice were divided into the following 4 experimental groups: control group (CG), low dose group (LG), middle dose group (MG) and high dose group (HG,). The control group was given 0.5% Tween 80 solution and the treatment groups (LG, MG, HG) were given various doses of glabridin (5, 10, 20 mg/kg) for 28 consecutive days. Body mass, blood lactic acid (BLA), serum blood urea nitrogen (BUN), liver glycogen and muscle glycogen concentrations in mice were determined. Results showed that glabridin significantly inhibited fatigue, which extended the exhaustive exercise time of mice, effectively delayed the elevation of blood lactic acid and increase in the storage of liver and muscle glycogen.

Differential role of nitric oxide (NO) in acute and chronic stress induced neurobehavioral modulation and oxidative injury in rats

The present study evaluated the effects of acute and chronic restraint stress (RS 1 h or 6 h), and their modulation by nitrergic agents on neurobehavioral and oxidative stress markers in rats. Acute RS (1 h or 6 h) reduced open arm entries (OAE) and open arm time (OAT) in the elevated plus maze test - which were attenuated by the NO precursor, L-arginine but not influenced appreciably by the NO synthase inhibitor, L-NAME. These behavioral changes were associated with differential changes in brain NO metabolites (NOx) but consistently reduced GSH and raised MDA levels in comparison to the control group. Following RS 1 h x 10 the neurobehavioral suppression and changes in brain oxidative stress markers were less pronounced as compared to the acute RS (1 h) group indicating adaptation. L-arginine pretreatment facilitated this adaptation to chronic RS (1 h). Interestingly RS 6 h x 10, induced severe behavioral suppression and aggravation of MDA and NOx levels and L-NAME pretreatment tended to protect against these chronic RS induced aggravations. These results suggest that acute and chronic RS induces duration/intensity dependent neurobehavioral and oxidative injury which are under the differential regulatory control of NO.

Constituents of Ocimum sanctum with antistress activity

Three new compounds, ocimumosides A (1) and B (2) and ocimarin (3), were isolated from an extract of the leaves of holy basil (Ocimum sanctum), together with eight known substances, apigenin, apigenin-7-O-beta-D-glucopyranoside, apigenin-7-O-beta-D-glucuronic acid ( 4), apigenin-7- O-beta- d-glucuronic acid 6''-methyl ester, luteolin-7-O-beta-D-glucuronic acid 6''-methyl ester, luteolin-7-O-beta-D-glucopyranoside, luteolin-5-O-beta-D-glucopyranoside, and 4-allyl-1-O-beta-D-glucopyronosyl-2-hydroxybenzene (5), and two known cerebrosides. The structures of the new compounds were determined on the basis of extensive 1D and 2D NMR spectroscopic analysis. The new compounds (1- 3) and the known compounds 4 and 5 were screened at a dose of 40 mg/kg body weight for acute stress-induced biochemical changes in male Sprague-Dawley rats. Compound 1 displayed promising antistress effects by normalizing hyperglycemia, plasma corticosterone, plasma creatine kinase, and adrenal hypertrophy. Compounds 2 and 5 were also effective in normalizing most of these stress parameters. In contrast, compounds 3 and 4 were ineffective in normalizing any of these effects.

Sensitization and conditioning as contributors to gastrointestinal vulnerability

Electric shocks are stressful and if signalled can result in Pavlovian conditioning of the stress response. Stress arising from such shocks or conditioned psychological "threat" influences vulnerability to gastrointestinal disorders. Reviewed are our studies with rats showing that unconditioned stress experiences sensitize the glandular portion of the stomach to later restraint-in-water induced erosions, as an animal model of ulcer disease. These stress effects are not attributable to corticoids but may be opioid/endorphin dependent. The unconditioned stress-induced sensitization is reduced by allowing the rat either control over or prediction of the shocks even though the direct experience with shocks is identical. Elicitation of the conditioned stress response by a signal during the ulcer induction or even shortly afterwards increases gastric vulnerability to erosions. We are now finding parallel unconditioned stress effects on colonic erosions and increases in intestinal permeability induced by dextran sulphate sodium, as an animal model of inflammatory bowel disease. We conclude that psychological context of past trauma and/or current threat increases vulnerability to gastrointestinal disorders.

Temperature and vascular volume effects on gastric ulcerogenesis after cord transection

Gastric ulcers are an important cause of morbidity and mortality in the critically ill, especially those with CNS injury. We used cervical spinal cord transection (CCT) in the rat to model these ulcers and examined the effect of core body temperature and vascular volume on gastric ulcerogenesis. Hypothermia significantly increased ulcerogenesis compared to euthermia, while maintained euthermia produced ulcer indices not different from sham surgery. Hypovolemia (10% blood volume withdrawal) significantly increased ulcerogenesis compared to hypervolemia (10% of blood volume crystalloid infusion) or sham surgery. These results support crystalloid infusion and maintenance of core body temperature in the clinical setting.

Analysis of the cold-water restraint procedure in gastric ulceration and body temperature

Gastric mucosal injury induced by body restraint can be enhanced when combined with cold-water immersion. Based on this fact, the present study had two main purposes: (i) to examine the contribution of each of these two forms of stress on the development of gastric ulceration and regulation of body temperature and (ii) to investigate the importance of the animal's consciousness on gastric ulceration induced by the cold-water restraint. Independent groups of animals were exposed for 3 h to one of the following stressful treatments: body restraint plus cold-water (20+1 degrees C) immersion, body restraint alone or cold-water immersion alone. Control animals were not exposed to any form of stress. Half of the animals submitted to each of the four treatments were anesthetized with thionembutal (35 mg/kg), whereas the other half was injected with saline. Results indicated that body restraint alone was not sufficient to induce gastric ulceration or changes in body temperature. On the other hand, cold-water exposure, either alone or in conjunction with body restraint, induced the same amount of stomach erosions and hypothermia. Therefore, it appears that body restraint does not play an important role on gastric ulceration induced by the cold-water restraint procedure. Present results also indicated that conscious and anesthetized animals immersed in cold water presented robust gastric ulceration and a marked drop in body temperature. However, conscious animals developed more severe gastric damage in comparison to anesthetized animals although both groups presented the same degree of hypothermia. These findings suggest that hypothermia resulting from cold-water exposure has a deleterious effect on gastric ulceration but the animal's conscious activity during the cold-water immersion increases the severity of gastric mucosal damage. It is concluded that cold-water restraint is a useful procedure for the study of the underlying mechanisms involved in stress-induced ulceration.

Effects of various Eleutherococcus senticosus cortex on swimming time, natural killer activity and corticosterone level in forced swimming stressed mice

The cortex of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. has been used extensively in Russia, China, Korea and Japan as an adaptogen whose properties are the ability to increase as non-specific body resistance to stress and fatigue. Although it has been reported that Eleutherococcus senticosus has anti-fatigue and anti-stress actions, their actions are still unclear on the relationship between immune system, especially natural killer (NK) activity and endocrine system (corticosterone level). We compared the effects of the water extracts (A, B, C, D and E) of five Eleutherococcus senticosus cortex on the swimming time, NK activity and blood corticosterone level using forced swimming stressed mice. Among five kinds, C, D and E extracts significantly prolonged the swimming time. C and D extracts inhibited the reduction of NK activity and the corticosterone elevation induced by forced swimming. The contents of eleutheroside E, isoflaxidin and eleutherosides B plus E were in the order C > D > E > B > A and C > E > D > A > B extracts, respectively. Therefore, it is suggested that eleutheroside E may be contributed to the anti-fatigue action, the recovery of the reduction of NK activity and the inhibition of corticosterone elevation induced by swimming stress.

Does Famotidine Induce Thrombocytopenia in Neurosurgical Patients?

The incidence of thrombocytopenia in neurosurgical patients prescribed famotidine is unknown. Using hospital records of neurosurgery patients treated between July 2001 and July 2002, a retrospective cohort study was performed comparing platelet counts in patients treated with famotidine with a similar group of patients who were not prescribed an H2 antagonist. Patients were excluded if: 1) platelets were less than 150,000 prior to famotidine administration; 2) pre-drug and post-drug platelets were not drawn; 3) they were concurrently taking a potential thrombocytopenic inducing drug; or 4) disseminated intravascular coagulation, thrombocytopenic purpura, or any other confounding hematologic disorder developed. Seventeen of 50 (34%) patients on famotidine developed thrombocytopenia compared with 11 of 98 (11.2%) of those untreated (P = 0.002). In this retrospective study, neurosurgical patients on famotidine developed thrombocytopenia statistically significantly more often than those untreated. Although no clinically significant sequelae developed as a result of the thrombocytopenia, if these findings are confirmed by a prospective study, proton pump inhibitors and sucralfate, with their similar efficacy, may be a better choice for gastrointestinal prophylaxis in neurosurgical patients.

Anti-inflammatory effect of acute stress on experimental colitis is mediated by cholecystokinin-B receptors

We aimed to investigate the effects of electric shock (ES) on the course of experimental colitis and the involvement of possible central and peripheral mechanisms. In Sprague-Dawley rats (n = 190) colitis was induced by intracolonic administration 2,4,6-trinitrobenzenesulfonic acid (TNBS). The effects of ES (0.3-0.5 mA) or the central administration of corticotropin-releasing factor (CRF; astressin, 10 microg/kg) or cholecystokinin (CCKB; 20 microg/kg) receptor antagonists and peripheral glucocorticoid receptor (RU-486; 10 mg/kg) or ganglion (hexamethonium; 15 mg/kg) blockers on TNBS-induced colitis were studied by the assessment of macroscopic score, histological analysis and tissue myeloperoxidase activity. ES reduced all colonic damage scores (p < 0.05-0.01), while central CRF (p < 0.05-0.001) and CCKB receptor (p < 0.05-0.01) blockers or peripheral hexamethonium (p < 0.05-0.01) and RU-486 (p < 0.05) reversed stress-induced improvement. ES demonstrated an anti-inflammatory effect on colitis, which appears to be mediated by central CRF and CCK receptors with the participation of hypothalamo-pituitary-adrenal axis and the sympathetic nervous system.

Prolactin prevents acute stress-induced hypocalcemia and ulcerogenesis by acting in the brain of rat

Stress causes hypocalcemia and ulcerogenesis in rats. In rats under stressful conditions, a rapid and transient increase in circulating prolactin (PRL) is observed, and this enhanced PRL induces PRL receptors (PRLR) in the choroid plexus of rat brain. In this study we used restraint stress in water to elucidate the mechanism by which PRLR in the rat brain mediate the protective effect of PRL against stress-induced hypocalcemia and ulcerogenesis. We show that rat PRL acts through the long form of PRLR in the hypothalamus. This is followed by an increase in the long form of PRLR mRNA expression in the choroid plexus of the brain, which provides protection against restraint stress in water-induced hypocalcemia and gastric erosions. We also show that PRL induces the expression of PRLR protein and corticotropin-releasing factor mRNA in the paraventricular nucleus. These results suggest that the PRL levels increase in response to stress, and it moves from the circulation to the cerebrospinal fluid to act on the central nervous system and thereby plays an important role in helping to protect against acute stress-induced hypocalcemia and gastric erosions.

Apomorphine-susceptible and apomorphine-unsusceptible Wistar rats differ in their recovery from stress-induced ulcers

The aim of the present study was to investigate the effects of restraint-in-water-stress on gastric ulcerations in two fundamentally different types of animals: the apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats. APO-SUS and APO-UNSUS do not only differ in their susceptibility to the dopamine agonist apomorphine, but also in stress-induced release of mesolimbic dopamine and corticosterone. All three factors are known to either predict or be involved in gastric ulceration. The results showed that immediately after the stressor the ulcerations in APO-SUS and APO-UNSUS rats were not line-specific. On the contrary, the recovery from gastric ulceration varied between both types of rat: APO-SUS rats did not show any sign of recovery after 6 hours whereas APO-UNSUS rats significantly recovered during the period of 0-6 hr after the stressor. It is hypothesised that this difference is due to the fact that APO-UNSUS rats are characterised by a less and shorter-lasting stress-induced increase of corticosterone. This study provides evidence that the pathological effects of exposure to stressors significantly differ between APO-SUS and APO-UNSUS rats and that genetic factors may direct the process of recovering from ulcers.

Marked suppression of gastric ulcerogenesis and intestinal responses to stress by a novel class of drugs

When exposed to prolonged stress, rats develop gastric ulceration, enhanced colon motility with depletion of its mucin content and signs of physiological and behavioral arousal. In this model, we tested whether antidepressants (fluoxetine and bupropion), anxiolytics (diazepam and buspirone) or the novel nonpeptide corticotropin-releasing hormone (CRH) type-1 receptor (CRH-R1) antagonist, antalarmin, modify these responses. Fluoxetine, bupropion, diazepam and antalarmin all suppressed stress-induced gastric ulceration in male Sprague-Dawley rats exposed to four hours of plain immobilization. Antalarmin produced the most pronounced anti-ulcer effect and additionally suppressed the stress-induced colonic hypermotility, mucin depletion, autonomic hyperarousal and struggling behavior. Intraperitoneal CRH administration reproduced the intestinal but not the gastric responses to stress while vagotomy antagonized the stress-induced gastric ulceration but not the intestinal responses. We conclude that brain CRH-R1 and vagal pathways are essential for gastric ulceration to occur in response to stress and that peripheral CRH-R1 mediates colonic hypermotility and mucin depletion in this model. Nonpeptide CRH-R1 antagonists may therefore be prophylactic against stress ulcer in the critically ill and therapeutic for other pathogenetically related gastrointestinal disorders such as peptic ulcer disease and irritable bowel syndrome.

Effect of Acanthopanax senticosus Harms on biogenic monoamine levels in the rat brain

The extract of the stem bark of Acanthopanax senticosus Harms (ASH) is known to have healing and protective effects on stress-induced disturbance of mental status. We have analysed whether a single or chronic (2 week) administration of ASH can affect concentrations of noradrenaline (NA), dopamine (DA) and their metabolites in the normal rat brain. A single p.o. administration of ASH elevated the NA and DA levels in the whole brain of rats in a dose-dependent manner. A single or 2 week administration of ASH (500 mg/kg) showed a marked increase in the DA level only in the striatum. However, NA levels were increased by a single dose of ASH in a wide range of brain regions such as the cortex, hypothalamus, striatum, hippocampus, substantia nigra and pons. When administered for 2 weeks no increase in NA levels was seen in these brain regions, except for an increase in the frontal cortex and anterior hypothalamus. The present results suggest that ASH may act by regulating NA and DA levels in specific brain regions related to stress response and Parkinson's disease.

The emergence test: effects of psychotropic drugs on neophobic disposition in Wistar Kyoto (WKY) and Sprague Dawley rats

1. The Emergence Test (ET), a variation of the open field test in which the rat is not handled, and is purported to measure neophobia, was applied to Wistar Kyoto (WKY) and Sprague Dawley (S-D) rats. 2. While no-stress control WKY rats were less active in the ET, pre-treatment with shock stress exacerbated strain differences. WKY rats, previously exposed to shock, did not emerge from the home cage start box during repeated testing, whereas previously stressed S-D rats vacated the home cage quickly and revealed increasing behavioral agitation. 3. Diazepam reduced emergence latency only in S-D rats, whereas nomifensine significantly increased head poke responses in WKY rats. 4. WKY rats responded to the ET with characteristically depressive behavior, whereas S-D rats responded to the same ET with behavioral agitation and anxiety. The implications of these behavior patterns for discriminating between anxiety and depressive behavior are presented.

Evaluation of subchronic toxicity of n-butyl acetate vapor

The subchronic toxicity of n-butyl acetate (nBA), a common industrial solvent, was tested in rats in a 13-week inhalation study. Male and female Sprague-Dawley (SD) rats were exposed to concentrations of 0, 500, 1500 or 3000 ppm nBA for 6 h per day, 5 days per week for 13 consecutive weeks. Transient signs of sedation were observed only during exposure to the 1500 and 3000 ppm concentrations. Body weights for the 1500 and 3000 ppm groups were significantly reduced. Feed consumption values for the 1500 and 3000 ppm groups were significantly lower than the control group. Weights of the liver, kidneys and spleen were significantly lower for the 3000 ppm male group; testes and adrenal gland weights for the 1500 and 3000 ppm groups and the lung weight for the 3000 ppm male group were significantly higher than for the control group. Signs of irritation of the glandular stomach and necrosis in the non-glandular stomach were observed in 3000 ppm female rats. Degeneration of the olfactory epithelium along the dorsal medial meatus and ethmoturbinates of the nasal passages of some 1500 and all 3000 ppm rats was also seen. The severity was mild to moderate for the 3000 ppm group and minimal to mild for the 1500 ppm group. No effects were observed in the lungs of any group. The no-observed-effect level (NOEL) for this study is considered to be 500 ppm. The data presented here are relevant to the toxicity risk assessment of n-butanol due to the rapid hydrolysis of nBA in vivo.

Catecholaminergic neurons in rat dorsal motor nucleus of vagus project selectively to gastric corpus

Nitric oxide synthase-immunoreactive (NOS-IR) neurons in the rat caudal dorsal motor nucleus of the vagus (DMV) project selectively to the gastric fundus and may be involved in vagal reflexes controlling gastric distension. This study aimed to identify the gastric projections of tyrosine hydroxylase-immunoreactive (TH-IR) DMV neurons, whether such neurons colocalize NOS-IR, and if they are activated after esophageal distension. Gastric-projecting neurons were identified after injection of retrograde tracers into the muscle wall of the gastric fundus, corpus, or antrum/pylorus before removal and processing of the brain stems for TH- and NOS-IR. A significantly higher proportion of corpus- compared with fundus- and antrum/pylorus-projecting neurons were TH-IR (14% compared with 4% and 2%, respectively, P < 0.05). Colocalization of NOS- and TH-IR was never observed in gastric-projecting neurons. In rats tested for c-Fos activation after intermittent esophageal balloon distension, no colocalization with TH-IR was observed in DMV neurons. These findings suggest that TH-IR neurons in the caudal DMV project mainly to the gastric corpus, constitute a subpopulation distinct from that of nitrergic vagal neurons, and are not activated on esophageal distension.

Is there a role for psychology in ulcer disease?

The discovery of the importance of bacterial factors in the etiology of ulcer disease has led to a neglect of psychological factors. However, both earlier theoretical and empirical approaches implicating these factors are supported by more recent studies, both epidemiological and experimental. While not ignoring the unquestioned role of Helicobacter, it is important for future research to recognize the multi-factorial nature of ulcer disease by which several factors, including stress, bacteria and non-steroid antiinflammatory drugs, may interact to drive a pre-pathology (erosions or ulcerations) to a pathological state (ulcer). Calls for general eradication programs should be cautioned in the light of possible unwanted side effects.

Restraint stress-induced alterations in the levels of biogenic amines, amino acids, and AChE activity in the hippocampus

Inspite of large number of studies on the neurochemical changes in the stress, an equivocal case is yet to be made for the role of a specific neurotransmitter in this important neurobiological disorder. The difficulty arises from the fact that there is no single neurotransmitter system appears to be responsible for the stress induced damage to the hippocampal neurons. The present study evaluates the effect of restraint stress on the alterations in the levels of biogenic amines, aminoacids and acetylcholinesterase activity in the hippocampus. Male Wistar rats of 45 days old were subjected to 6 hours of daily restraint stress over a period of 21 days. Immediately after the last session of stress, rats were sacrificed and neurotransmitter levels were estimated in the hippocampus. A significant (p < 0.001) decrease in the levels of noradrenaline, dopamine, 5-hydroxytryptamine and acetylcholinesterase activity in the stressed rats was observed compared to controls. However, levels of glutamate was significantly (p < 0.001) increased in stressed rats. These results indicate that chronic restraint stress decreases aminergic and cholinergic neurotransmission, and increases the glutamatergic transmission in the hippocampus.

Importance of endogenous nitric oxide synthase in the rat hypothalamus and amygdala in mediating the response to capsaicin

Although capsaicin has been shown to activate certain neuronal groups in the hypothalamus and amygdala, the neurotransmitters involved and the exact mechanism of action are not clearly understood at present. The aim of this study was to examine the hypothesis that the effect of capsaicin in the rat hypothalamus and amygdala primarily involves direct activation of the endogenous nitric oxide synthase (NOS) neurons responsible for the synthesis of nitric oxide (NO). Subcutaneous capsaicin injection in male rats, compared with vehicle, caused a significant increase in Fos expression in the paraventricular nucleus (PVN), supraoptic nucleus (SON), and medial and cortical amygdala. The expression of nicotinamide adenine dinucleotide phosphate diaphorase, a histochemical marker for NOS, was also increased in these brain areas in addition to the periventricular and lateral hypothalamic area and central amygdaloid nucleus. Also, capsaicin significantly increased the expression of neuronal NOS messenger RNA and protein in the PVN, SON, and medial amygdala as demonstrated by in situ hybridization and immunohistochemistry, respectively. A higher proportion of the NOS neurons in the PVN, periventricular region, SON and amygdala showed Fos expression in response to capsaicin than vehicle injection. There was little, if any, Fos activation in the NOS-positive neurons in the lateral hypothalamic area. The capsaicin-induced activation of the hypothalamic PVN and SON neurons and the medial amygdaloid nucleus was attenuated in the NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) -pretreated animals in comparison with the inactive enantiomer D-NAME. These observations indicate that activation of the endogenous NOS system and production of NO constitute a major pathway through which capsaicin exerts its effect within the hypothalamus and amygdala.

Anxiety and helplessness in the face of stress predisposes, precipitates, and sustains gastric ulceration

When an organism is subjected to stress, gastric ulcers or ulcerations commonly develop but the vulnerability to and amount of pathology induced varies considerably between individuals. The role of psychological factors in determining the occurrence and severity of these ulcerations is amply demonstrated in the studies reviewed here. The present paper (a) gives a brief history of the search for the causes of gastric ulcer, (b) provides a review of our own research which reveals that vulnerability to gastric ulceration is modulated by psychologically meaningful experiences, and (c) offers a multifactorial perspective on the causes of gastric ulceration and the future of research on it.

Intracisternal PYY inhibits gastric lesions induced by ethanol in rats: role of PYY-preferring receptors?

We previously reported that intracisternal (i.c.) injection of peptide YY (PYY) and low doses of thyrotropin-releasing hormone (TRH) or TRH analog, RX 77368, increased the resistance of the gastric mucosa to ethanol injury through vagal pathways in rats. The gastroprotective effect of i.c. injection of PYY/neuropeptide NPY (NPY) agonists with differential in vitro affinity to the Y receptor subtypes was examined in urethane-anesthetized rats. Intragastric administration of ethanol (45%, 5 ml/kg) results in mucosal lesions covering 23+/-2% of the gastric corpus in 1 h. PYY (500 ng, i.c.) significantly reduced ethanol-induced gastric lesions by 52%. [Pro34]PYY (PYY-preferring/Y1/Y5/Y4 subtypes) injected i.c. at 50, 100, 200 or 500 ng, reduced dose dependently gastric lesions to 15.4+/-2.2%, 11.4+/-3.1%, 8.6+/-2.9% and 5.4+/-2.2%, respectively. PYY3-36, (Y2/Y4 subtypes), [Leu31, Pro34]NPY (Y1/Y5), NPY (Y3/Y1/Y5/Y2) and pancreatic polypeptide (PP, Y4) injected i.c. at 500 ng did not influence significantly ethanol-induced gastric lesions. Combined i.c. injection of RX 77368 (1 ng) and Pro34PYY (25 ng), at sub-threshold doses given singly, reduced ethanol-induced gastric injury to 12.9+/-2.3% while RX 77368 (1 ng) plus PYY3-36 (500 ng) or [Leu31, Pro34]NPY (25 ng) had no effect. These findings indicate that i.c. PYY-induced gastric protection against 45% ethanol is mediated by a Y receptor subtype which bears similarity with the putative PYY-preferring receptor and distinct from the currently defined Y1/Y5; in addition, there is a synergistic interaction between activation of this PYY-preferring receptor and i.c. TRH to increase the resistance of the gastric mucosa to injury caused by 45% ethanol.

Effects of conditioning stimulation of the central amygdaloid nucleus on tooth pulp-driven neurons in the cat somatosensory cortex (SI)

To study the limbic control of nociception, we examined the effect of conditioning stimulation of the central amygdaloid nucleus (ACE) on tooth pulp-driven (TPD) neurons in the first somatosensory cortex (SI). Cats were anesthetized with N(2)O-O(2) (2:1) and 0.5% halothane, and immobilized with tubocurarine chloride. The tooth pulp test stimulus was applied by a single rectangular pulse (0.5 ms in duration and 3-5 times the threshold intensity for the jaw-opening reflex). Conditioning stimuli to the ACE consisted of trains of 33 pulses (300 microA) delivered at 330 Hz at intervals of 8-10 s. In 35 out of 61 of the slow (S)-type TPD neurons with latencies of more than 20 ms, conditioning stimulation in the ACE, especially in the medial division, markedly reduced the firing response to the pulpal stimulation. The inhibition of the firing rate in the S-type neurons was 74% of the control. In these S-type neurons, the neurons that were inhibited had significantly longer latencies compared to the non-inhibited neurons (45.0 +/- 17.6 ms, n = 32 vs. 34.8 +/- 10.5 ms, n = 26). In contrast, the ACE conditioning stimulation affected only one out of 18 fast-type TPD neurons with latencies of less than 20 ms. In addition, ACE stimulation had no effect on the spontaneous discharges of either S-type or F-type neurons. The ACE inhibitory effect on S-type neurons was not diminished by naloxone administration (1 mg/kg, I.V. ), while the blockade of histamine H(1)-receptor by diphenhydramine hydrochloride (0.5 mg/kg, I.V.) partially reversed the inhibitory effect. These results suggest that the ACE inhibits ascending nociceptive information to the SI and that this inhibition is mediated in part by histamine (H(1)) receptors. It seems likely that the antinociceptive effect is a neurophysiological basis for stress-induced analgesia (SIA).

Gender differences in acute and chronic stress in Wistar Kyoto (WKY) rats

While females are considered more susceptible to depressive behavior, this assertion is not strongly supported by the experimental literature. Since stress contributes to depressive behavior, male and female Wistar Kyoto (WKY) rats were exposed to either one session (acute stress) or 5 sessions (chronic stress) of restraint plus cold in order to study depressive behavior in male and female rats. After their respective treatment exposure, rats were tested in the open field test (OFT) and for retention of a passive-avoidance (P-A) task. One stress session resulted in significant immobility in the OFT for males, whereas 5 sessions were required to produce similar immobility in female rats. Acute stress interfered with the retention of the P-A response for males, while both acute and chronic stress produced poor P-A responses in female rats. Food consumption decreased progressively, as a function of stress sessions, in female rats, whereas feeding in males returned to control levels after five stress days. Both acute and chronic stress exacerbated the stress ulcer response in male rats, but not in female rats. Chronic, but not acute, stress resulted in an increase in serotonin transporter mRNA levels in the dorsal raphe nucleus of both male and female rats. The general consensus from these data suggested that female rats were more vulnerable to chronic stress and consequently supported the notion that females may be more susceptible to stress-induced behavioral depression. Key Words: WKY rats, acute and chronic stress, gender, passive avoidance, open field behavior, stress-ulcer, adrenal weight, serotonin, dorsal raphe nucleus

The origin of catecholaminergic nerve fibers in the subdiaphragmatic vagus nerve of rat

It is known that the vagus nerve contains catecholaminergic fibers. However, the origin of these fibers has not been systematically examined. In this study, we addressed this issue using retrograde tracing from the subdiaphragmatic vagus nerve combined with immunocytochemistry. The cervical and thoracic sympathetic trunk ganglia, the nodose ganglia and the dorsal motor nucleus of the vagus nerve were examined following injection of Fluoro-Gold or cholera toxin horseradish peroxidase conjugate into the trunks of the subdiaphragmatic vagus nerve of rats. Numerous retrogradely labeled neurons were seen in the nodose ganglion and the dorsal motor nucleus of the vagus nerve. Very few labeled neurons were found in the sympathetic ganglia (less than 0.06% of the neurons in either superior cervical ganglion or cervicothoracic ganglion were retrogradely labeled). Double labeling with immunofluoresence for catecholamine synthesizing enzymes revealed that: (1) 92% of all Fluoro-Gold retrogradely labeled tyrosine hydroxylase immunoreactive neurons were found in parasympathetic sources (75% in the dorsal motor nucleus of the vagus nerve and 17% in the nodose ganglia), and only 8% in the cervicothoracic sympathetic ganglia; (2) 12% of the retrogradely labeled catecholaminergic neurons in the dorsal motor nucleus of the vagus nerve were also dopamine-beta-hydroxylase immunopositive neurons; (3) 70% of the retrogradely labeled neurons in the sympathetic ganglia were tyrosine hydroxylase immunopositive and 54% of these catecholaminergic neurons contained dopamine-beta-hydroxylase, while 30% of the retrogradely labeled neurons were non-catecholaminergic neurons. These results indicate that catecholaminergic fibers in the abdominal vagus nerve are primarily dopaminergic and of parasympathetic origin, and that only an extremely small number of these fibers, mostly noradrenergic in nature, arise from postganglionic sympathetic neurons.

Lateralized effects of medial prefrontal cortex lesions on neuroendocrine and autonomic stress responses in rats

The medial prefrontal cortex (mPFC) is highly activated by stress and modulates neuroendocrine and autonomic function. Dopaminergic inputs to mPFC facilitate coping ability and demonstrate considerable hemispheric functional lateralization. The present study investigated the potentially lateralized regulation of stress responses at the level of mPFC output neurons, using ibotenic acid lesions. Neuroendocrine function was assessed by plasma corticosterone increases in response to acute or repeated 20 min restraint stress. The primary index of autonomic activation was gastric ulcer development during a separate cold restraint stress. Restraint-induced defecation was also monitored. Plasma corticosterone levels were markedly lower in response to repeated versus acute restraint stress. In acutely restrained animals, right or bilateral, but not left mPFC lesions, decreased prestress corticosterone levels, whereas in repeatedly restrained rats, the same lesions significantly reduced the peak stress-induced corticosterone response. Stress ulcer development (after a single cold restraint stress) was greatly reduced by either right or bilateral mPFC lesions but was unaffected by left lesions. Restraint-induced defecation was elevated in animals with left mPFC lesions. Finally, a left-biased asymmetry in adrenal gland weights was observed across animals, which was unaffected by mPFC lesions. The results suggest that mPFC output neurons demonstrate an intrinsic right brain specialization in both neuroendocrine and autonomic activation. Such findings may be particularly relevant to clinical depression which is associated with both disturbances in stress regulatory systems and hemispheric imbalances in prefrontal function.

Water immersion-restraint stress induces expression of immediate-early genes in gastrointestinal tract of rats

The aims of this study were to determine 1) which cells are involved in stress-induced acute gastric mucosal lesion and 2) what kinds of molecular alterations are induced by stress, using immediate-early genes (IEG) as tools for detection of cellular activation. Male Wistar rats were exposed to acute water immersion-restraint stress. Protein and mRNA for IEG were detected by immunohistochemistry and in situ hybridization, respectively. This stress induced the expression of c-fos and nerve growth factor-induced gene (NGFI-A) mRNA in gastric epithelial cells, the smooth muscle layer of small blood vessels, and the stomach wall. Stress upregulated the mRNA levels of these IEG in the duodenal epithelial cells and induced de novo expression of IEG in the smooth muscle layer of small blood vessels and the duodenal wall. These findings indicate that these cells are activated in response to stress. Expression of these IEG and/or transcriptional factors may reflect an initiation of mechanisms for repairing the lesions induced by stress as well as an adaptation to the stress.

Gastric ulcer formation in cold-stressed mice related to a central calcium-dependent-dopamine synthesizing system

Stress ulceration of the stomach in mice was investigated from the aspect of the calcium/calmodulin-dependent dopamine synthesizing system in the brain. Cold stress was induced in mice by restraining them at 4 degrees C. Serum and brain calcium levels were increased by cold stress, and an increased brain calcium level was found to enhance dopamine synthesis and a successively increased brain dopamine level induced gastric ulcer formation. Development of gastric ulcers elicited by cold stress was significantly decreased by i.p. pretreatment with EDTA (1 micromol/mouse, 1 h before restraint) or alpha-methyltyrosine (a tyrosine hydroxylase inhibitor, 100 mg/kg, 24 h before restraint), and was further significantly increased by pretreatment with CaCl2 (40 micromol/kg, 1 h before restraint). These findings suggest that the development of gastric ulcers in cold-stressed mice may be linked with the enhancement of calcium/calmodulin-dependent catecholamine synthesis in the brain.

Intrinsic and extrinsic connections of the rat central extended amygdala: an in vivo electrophysiological study of the central amygdaloid nucleus

Anatomical studies have shown that the central amygdaloid nucleus (CeA) is reciprocally connected with the lateral bed nucleus of the stria terminalis (BSTL), both structures being major components of the central extended amygdala. The CeA also receives projections from the insular cortex (InsCx) and the paraventricular thalamic nucleus (PVT). Extracellular unit activity was recorded from neurons in the lateral CeA (CeL) in urethane anaesthetized rats and their responses were studied after electrical stimulation of the BSTL, InsCx and PVT. The spontaneous activity of CeL neurons was low (1.69 spikes/s) and 40% of recorded cells were silent. The iontophoretic application of the GABAA antagonist, bicuculline, increased the firing rate of 20% of neurons. The BSTL stimulation induced an antidromic response in 33% of the tested cells. Orthodromic responses were obtained from 83% (BSTL stimulation), 70% (InsCx stimulation) and 85% (PVT stimulation) of tested cells, some of which responded to both BSTL and InsCx or PVT stimulations. Orthodromic responses mostly consisted in 1-3 orthodromic spikes followed by an inhibition. During iontophoretic application of bicuculline, stimulation induced additional short latency orthodromic spikes, even in cells that were previously unresponsive. However, the duration of the inhibition was never reduced. These results indicate that GABAergic neurotransmission may play a dominant role in both spontaneous and evoked electrical activities in the CeL, probably mediated by local circuit cells involved in a feed-forward inhibition. This organization, along with the reciprocal connections between the CeL and the BSTL, is considered in the context of the extended amygdala.

Dopamine produced by the stomach may act as a paracrine/autocrine hormone in the rat

Dopamine (DA) has been suggested to be a protective factor in the gastrointestinal tract but neither a source of DA nor its exact targets of action have been identified. In this study, we demonstrate high levels of DA (and DOPA) which persist after chemical sympathectomy in the gastric juice of rats. Immunostaining and in situ hybridization histochemistry reveal the presence of tyrosine hydroxylase (TH), DA transporter and vesicular monamine transporters in the acid-producing parietal cells. Like DA, TH enzyme activity remains after chemical sympathectomy. We also demonstrate active reuptake and storage of DA that indicates a regulated release of this neurohormone from parietal cells. DA D1b receptor mRNA is the most abundant DA receptor subtype in gastric and duodenal epithelium. Therefore, we suggest that selective DA D1b receptor agonists may be useful adjuncts in the treatment of duodenal and gastric ulcers. Gastric epithelia possess the hallmarks of functional DA neuroendocrine cells, suggesting that DA has an important role in self-protective mechanisms of the gastrointestinal tract. These findings should allow elucidation of DA role in normal and disease states in the stomach and duodenum.

Autonomic regulation of gastric ulcerogenesis after cervical cord transection in the rat

OBJECTIVE

To examine the role of anticholinergic and sympathomimetic drugs in preventing gastric ulcerogenesis after cervical cord transection (CCT) in the rat.

METHODS

A randomized, prospective, interventional trial was performed comparing pirenzepine (muscarinic type I receptor antagonist) and ephedrine (nonspecific sympathomimetic) in the prevention of gastric ulcerogenesis after CCT in the rat. After isoflurane-induced general anesthesia, group 1 (n = 12) received sham CCT with no pretreatment, group 2 received CCT with no pretreatment, group 3 received CCT with pirenzepine pretreatment (0.01/mg/kg IP), and group 4 received CCT with ephedrine pretreatment (3 mg/kg IP). Six hours after intervention, all the rats were euthanized with isoflurane, stomachs were dissected, and a gastric ulcer index was determined.

RESULTS

The mean (+/- SD) ulcer index was 0.08 +/- 0.1 for group 1, 2.33 +/- 0.5 for group 2 (p = 0.01), 0.41 +/- 0.7 for group 3 (p = 0.037 compared with group 2), and 0.75 +/- 0.7 for group 4 (p = 0.0005 compared with group 2). Groups 3 and 4 were not significantly different from each other (p = 0.30).

CONCLUSIONS

Gastric ulcerogenesis after CCT in the rat is decreased by anticholinergic and sympathomimetic drug pretreatment.

Expression of aggression attenuates both stress-induced gastric ulcer formation and increases in noradrenaline release in the rat amygdala assessed by intracerebral microdialysis

The effects of an aggressive biting response on stress-induced noradrenaline (NA) release in the rat amygdala and gastric ulcer formation were studied with an intracerebral microdialysis technique. Rats were exposed to a 60-min period of cold restraint stress with or without being allowed to bite a wooden stick. They were sacrificed 100 min after release from stress to investigate gastric ulcer formation. Cold-restraint stress increased NA release to 304 +/- 22.3 and 206 +/- 23.8% of basal levels (mean +/- SEM) in the nonbiting and biting groups, respectively. The stress-induced increases in NA release in the nonbiting group were significantly higher than those in the biting group. In the nonbiting group, significant increases in NA release continued for 80 min after release from stress; however, NA levels in the biting group recovered to basal levels immediately after the cessation of stress. Although many severe gastric lesions with bleeding were found in the nonbiting group, fewer gastric lesions without bleeding were found in the biting group. The cumulative length of gastric lesions in the nonbiting group and in the biting group was 26.2 +/- 7.4 and 6.8 +/- 3.9 mm (mean +/- SEM), respectively. The mean number of ulcers in the nonbiting group and the biting group was 11.8 +/- 1.3 and 1.8 +/- 0.7 (mean +/- SEM), respectively. Both the cumulative length of ulcers and the number of ulcers were significantly lower than those seen in the nonbiting group. These findings strongly suggest that expression of aggression during stress exposure attenuates not only stress-induced increases in NA release in the rat amygdala but also gastric ulcer formation consequent to stress.

Effect of acute or repeated stress on behavior and brain norepinephrine system in Wistar-Kyoto (WKY) rats

WKY rats develop more restraint-induced gastric ulcers and exhibit more depressive behavior compared to other rat strains. Exposure to novel stressors for 21 days exacerbates depressive behavior in WKY rats and alters beta-adrenoceptors (beta-ARs) and norepinephrine transporter (NET) sites in several limbic brain regions when compared to Sprague-Dawley rats. The present study examined whether these effects would be elaborated following an acute stressor and whether WKY rats would demonstrate adaptation after repeated stress. Rats were subjected to a 2-h supine restraint stress for either one or eight consecutive daily sessions. Open-field behavioral data were collected immediately after the daily stress sessions. Brains were sectioned for autoradiographic analysis of 125I-pindolol binding to beta-ARs and 3H-nisoxetine binding to NET sites in discrete brain regions. Acute 1-day stress resulted in a significant drop in body weight and an inhibition of behaviors in the open field. These effects were also sustained following 7 days of chronic restraint stress. In contrast, while acute stress had no effect on NET binding sites or beta-ARs, repeated stress decreased NET sites in the amygdala, hypothalamus, and locus coeruleus with little effect on beta-ARs in the brain regions examined.