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Biomedical subjects

R Murison

Publications and source records attributed to R Murison.

49 records · Page 3Linked to original sources
PubMed1986

The ulcerogenic effect of a rest period after exposure to water-restraint stress in rats.

Shock-induced gastric ulceration in rats is exacerbated by allowing animals to rest between the period of stress and sacrifice. Conflicting data have been reported for similar post-stress rest effects using restraint stress. In Experiment 1, rats restrained in water for 2 h and then allowed a 2-h rest period exhibited significantly greater gastric ulceration than rats sacrificed immediately after the 2-h restraint-in-water stress period. The strength of this phenomenon is confirmed by Experiment 2, in which rats challenged with restraint in water for 1.25 h and then allowed a 1.25-h rest period before sacrifice exhibited greater ulceration than animals maintained in the restraint-in-water stress for the full 2 1/2 h. Corticosterone levels for these two treatment groups were similar at the time of sacrifice. Post-stressor rest therefore actively contributes to the ulcerogenic processes initiated by this form of stress challenge.

Animals↗
PubMed1986

Serial stressors: prior exposure to a stressor modulates its later effectiveness on gastric ulceration and corticosterone release.

Several studies have focused on the proactive effects of prior exposure to a stressor on ulcerogenic and endocrine responses to exposure to a similar final stressor. In the present study, we explored the effects of prior exposure of Møll-Wistar rats to water-restraint stress on gastric ulceration and corticosterone responses to a final stressor. The number of prior exposures to water-restraint challenge was varied from one to four, and the durations of the prior exposures varied from 30 min to 2 h. The duration of the final stress challenge was 75 min. The two indices of the stress response to the final stressor challenge yielded different results. For neither index was the duration of prior exposures a significant factor in modulating the response to the final challenge. For gastric ulceration, those animals receiving one prior exposure, but not four, exhibited less gastric ulceration than animals receiving no prior exposure. These animals also developed less ulceration than those receiving four prior exposures. For corticosterone, those animals receiving four prior exposures exhibited a lower adrenocortical response to the final stressor than did animals receiving no prior exposure, or only one prior exposure. The results indicate the complexity of proactive effects of earlier stress experience on responses to a final stressor challenge.

Adrenal Cortex↗
PubMed1986

Ethical issues in stress research: facts, fiction, and rational decisions.

The controversy over the use of animals in stress research is partly based on the assumption that we know what is and what is not stressful and pathological for the organism. The data show that our intuitive preconceptions are often misguided. Any understanding of the stress phenomenon and its relationship to disease must be founded on hard empirical data. Discussion of the use of animals in stress research should also take into account the consequences of work in this area for the well-being of animals and man.

Adrenal Cortex↗
PubMed1984

Plasma corticosterone and meal expectancy in rats: effects of low probability cues.

The plasma corticosterone levels of rats were examined prior to their morning meal on Days 1, 7 and 20 of a regimen of 1 hr access daily to food mash and water. The relationship between external cues and meal provision was varied by feeding some groups immediately upon room entry each morning, and others with a variable interval 90-min delay. On Day 1, corticosterone levels of the hungry rats were elevated around the time of light onset, and until 90 min following room entry. On Day 7, corticosterone levels increased in response to room entry in the delay-fed rats, but did not increase further in immediately fed rats. These results were interpreted as indicating that low, but nonzero, expectancy of meal availability elevates corticosterone levels. On Day 20, the immediately fed rats showed a dip in corticosterone levels after room entry, responding to cues highly predictive of imminent meal availability. Delay-fed rats no longer showed an elevation to room entry. The relationship between corticosterone level and meal expectancy is essentially curvilinear in the hungry rat. The corticosterone levels are high when there is uncertainty about whether food is coming or not, and low when there is a very high or very low probability that food is coming.

Animals↗
PubMed1983

The effect of sleep deprivation and recovery sleep on plasma corticosterone in the rat.

The effect of 24-h sleep deprivation by forced locomotion on plasma corticosterone was investigated in the rat. Corticosterone was slightly elevated after 21.5 h sleep deprivation, but did not differ from controls after a 2.5-h recovery period. An acute 20-min forced locomotion period caused a marked rise in plasma corticosterone. It is concluded that stress is not a major factor contributing to the massive effects of sleep deprivation on sleep parameters.

Animals↗
PubMed1982

Sleep deprivation procedure produces stomach lesions in rats.

Sprague-Dawley male rats were deprived of food for 40 hr and subjected to sleep deprivation by the "flower pot" or handling intervention procedures during the final 24 hr. Five of six rats in the flower pot group exhibited stomach erosions. Only one rat in the handling group, and no rats in a food deprived control group showed such erosions. The flower pot group also had higher levels of corticosterone than the food deprived control group. These findings argue for more serious consideration of the effects of the stress of procedures for sleep deprivation.

Animals↗
PubMedDate not supplied

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.

Animals↗
PubMedDate not supplied

Voluntary alcohol consumption in rats: relationships to defensive burying and stress gastric erosions.

Rats with short latency to initiate burying in the defensive burying test later showed lower alcohol consumption in an ethanol preference test than animals with medium and long latencies. These short-latency, or "active" animals also had a slight tendency to develop more ulceration than the "passive" animals. In addition, there was a negative correlation between voluntary alcohol consumption and the amount of stress-induced stomach ulcers. Many researchers view active burying behaviour as an index of anxiety. Our results suggest the opposite: that passivity, rather than active burying, may be an index of anxiety and that such passive animals subsequently ingest more ethanol. The tendency of active animals to develop more ulcers than passive animals is in contradiction to earlier studies. Our interpretation is that the long-latency animals experience more fear in the defensive burying test, with increased alcohol consumption as a result. This increase in alcohol consumption gives a cumulative cytoprotective effect against stomach ulcers.

Alcohol Drinking↗
PubMedDate not supplied

The neurobiology of stress ulcers.

We have reviewed the neurobiology of stress ulcers from animal models to potential pharmacotherapeutic mechanisms. The evidence strongly supports the hypothesis that certain stress-related gastric lesions are 'brain-driven' events which may be more effectively managed through central manipulations than by altering local, gastric factors. Recent advances in the use of anxiolytic and antidepressant drugs in the management of stress-related gastric mucosal injury further supports the contention that a brain-gut axis, which may have nervous, peptidergic and classic monoaminergic components, modulates the intricate and complicated pattern of communication between the brain and the stomach. Delineation of the precise pathways which make up this communication as well as their manipulation by various pharmacological agents will be the focus of future research endeavour.

Animals↗
PubMedDate not supplied

Behavioural responses to elevated plus-maze and defensive burying testing: effects on subsequent ethanol intake and effect of ethanol on retention of the burying response.

Based upon repeated observations of a relationship between defensive burying (DB), ethanol intake and stress ulcer susceptibility, and recurring questions regarding what DB behaviour reflects, two experiments were performed. Experiment 1 showed that prod shock exposure per se reduced subsequent ethanol intake, as did access to burying material. In rats without burying material in the conditioning phase, subsequent access to ethanol resulted in reduced DB activity in the retest, pointing to some interference by ethanol on latent learning. Experiment 2 showed that there were no effects of anxiety as measured in the elevated plus-maze (EPM) on saccharin or ethanol intake. Behaviours in the EPM and DB test did not correlate. Rats entering the open arm on first entry into the EPM drank and preferred more ethanol than those choosing the closed arm. Saccharin intake was negatively related to burying latency, and positively related to initial ethanol intake. In conclusion, it is still questionable whether the DB test is measuring anxiety, but exposure to the test or performance of the DB activity appears to cause modifications, psychologically and perhaps physiologically, in rats. Ethanol intake may under certain conditions interfere with the acquisition of a defensive response. The testing of DB behaviour may be useful in studying drug effects on latent learning of prepared responses.

Adaptation, Psychological↗