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Intensive repeated momentary diary techniques, such as the experience sampling method (ESM), place considerable burden on study participants by repeatedly prompting them to fill in a questionnaire several times throughout the day. The objective of this study was to investigate the level of disturbance reported by participants and predictors thereof using a pooled dataset of seven ESM studies including 1319 healthy participants and individuals with different mental health conditions. All studies used a design of 10 prompts per day over the course of 4 to 6 days. Participants reported no disturbance at 37% of the measurement occasions and the overall level of disturbance was relatively low. Also, clinical samples did not report significantly different levels of disturbance compared to the healthy participants. However, higher levels of disturbance were found for later study days, in the morning, and on weekends. Also, younger participants reported feeling more disturbed by the prompts. In terms of momentary states, higher levels of activity, activity stress, and tiredness were associated with higher disturbance. Also, participants experienced more disturbance when in company compared to when alone, and the level of disturbance increased when in company with less familiar people. Our findings suggest that studies using high-frequency ESM protocols can be used in mental health research, but researchers should be aware of the possible disturbance caused by their research design.

Companion animals have been identified as a unique source of social support and as contributors to mental wellbeing. This study uses the Experience Sampling Method to test whether this effect is due to stress-buffering. A total of 159 dog and cat owners responded to a series of randomly scheduled questionnaires on their smartphones. At each measurement moment, they reported in whether a pet is present at that moment and to what extent they have interacted with the pet. They also reported on stressful activities and events and on their current positive (PA) and negative (NA) affect. Multilevel regression analyses showed that when a companion animal was present (vs. absent) the negative association between stress and PA is less pronounced (event stress: B = 0.13, p = 0.002, 95% CI = 0.05, 0.21 activity stress: B = 0.08, p &lt, 0.001, 95% CI = 0.04, 0.12). No additional main effect was revealed when tested in a subsample of records that reported low or no stress. Main effects were found for the presence of a companion animal on negative affect (B = 0.08, p &lt, 0.001, 95% CI = 0.12, 0.05) and for interacting with a companion animal on positive affect (B = 0.06, p &lt, 95% CI = 0.04, 0.08). This shows that the presence of a companion animal buffers against the negative consequences of stress on positive affect, indicating stress-buffering as a mechanism behind the pet-effect. It is, however, not the only mechanism and more research is required to further elucidate how companion animals contribute to human wellbeing.

Objective To verify the difference between the masticatory muscles’ electrical activity, stress signals and the posture of preadolescents and adolescents with and without temporomandibular dysfunction (TMD). Methods 24 preadolescents and adolescents aged between 11 and 18 years old were divided into two groups, TMD group (TMDG) and control group (CG). All subjects were submitted to anthropometric measurements, psychological stress analysis, temporomandibular joint clinical evaluation and TMD verification; postural evaluation and masseter and temporal muscles electrical activity analysis during chewing. For statistical analysis, the Student's t-test or Mann-Whitney U test were used according to data distribution. Results There was a significant difference between the groups for the electrical activity of the right temporal muscles (7.43% ± 2.92 vs. 11.71% ± 5.37) and left (7.70% ± 4.04 vs.11.44% ± 4.03) in the inactive period of chewing between CG and TMDG, respectively. There was no difference in stress or posture variables between groups. Conclusions During the inactive period of chewing, there was greater activation of the temporal muscles in the TMDG. Female gender was prevalent in TMDG. The study participants showed signs of stress, regardless of the group. The posture and TMD relationship still need to be studied.

The review is dedicated to analysis of data available at present time concerning possible influence of stress upon telomere lengths and telomerase activity, as well as various ways of counteracting it. Present-day telomerase theory of aging gains a new impetus, shedding light upon the influence of psychological state of humans and their ability to counteract stress, upon the process of aging. It also tends to regard telomere shortening and the decrease in the activity of telomerase as a marker of level of the ability to adapt to both inner and outer influences. Both aging and age-dependent diseases are proved to be substantially retarded not only by the administration of drugs, but also by psychological means, which forms a good way towards healthy longevity. With complete understanding of the impossibility to prevent or even to slow down natural senescence itself, these methods allow to remove causes, which accelerate senescence, and to increase the average human longevity.

Travel and activity scheduling decisions largely depend on travelers’ responses to prevailing trip conditions. These could be impacted by environmental situations, such as adverse weather, which can increase the variability in travel times, practical capacity and other system properties. Understanding and modeling the relationship between travel and activity decisions and adverse weather is important for devising and evaluating transportation management strategies that rely on adjustments and shifts in behavior. This study focuses on the impact of rainfall precipitation on activity decisions, more specifically the perceived stress underlying these decisions. In the current study, activity scheduling decisions for discretionary activities are examined under different rainfall levels, but given consistent data on other forms of precipitations, such as snow sleet or hail, this study could be extended to these cases. Activity stress is modeled under a discrete choice framework. The results show that the perceived activity stress differs under rainfall to some extent, depending on the number of activities in a traveler’s activity queue, and the number of activities completed. The study also reveals that travel behavior may differ under rainfall, suggesting that travelers’ may perceive information and uncertainty differently, relative to conditions with less variability in weather. Furthermore, issues concerning climatology data requirements for transportation models are discussed.

Stress is a state of threatened homeostasis that produces different physiological as well as pathological changes depending on severity, type and duration of stress. The animal models are pivotal for understanding the pathophysiology of stress-induced behavioral alterations and development of effective therapy for its optimal management. A battery of models has been developed to simulate the clinical pain conditions with diverse etiology. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. The present review describes the different types of acute and chronic stress models including immersion in cold water with no escape, cold environment isolation, immobilization/restraint-induced stress, cold-water restraint stress, electric foot shock-induced stress, forced swimming-induced stress, food-deprived activity stress, neonatal isolation-induced stress, predatory stress, day-night light change-induced stress, noise-induced stress, model of post-traumatic stress disorder and chronic unpredictable stress models.

A water-soluble chicken extract is popularly consumed as a traditional health food. The studies made revealed that it could increase the survival time and inhibit the increase of locomotor activity in rats loaded with food-deprived activity stress. The mechanism for this might be related to an elevation of the brain histamine level, and the active ingredient, carnosine, might contribute to this effect.

Although past research has indicated that stress and the accompanying increase in glucocorticoids compromises hippocampal neurons, little is known about the effect of stress on hippocampal glial cells. In the current study, male rats were exposed to activity-stress (A-S) for six days; this comprised housing with an activity wheel and restricted access (1h/day) to food. Physiological data (e.g., relative adrenal and thymus weights, gastric ulceration) suggested that the A-S rats experienced more stress than pair-fed (no wheel) and control (fed ad libitum, no wheel) rats. Whereas stress did not influence the quantitative morphology of glial fibrillary acidic protein (GFAP)-immunoreactive cells, a semi-quantitative analysis revealed that the A-S rats had significantly more (30%) GFAP-immunoreactive cells in the hippocampal CA3 region than the control rats. Based on the present findings, it appears that the hippocampal astrocytic response to chronic stress may be similar to the response found in endangered, or challenged hippocampal environments, such as in ischemia.

In order to investigate the recovery from activity-stress ulcers by ad lib-feeding and/or cessation of running, male Wistar rats were exposed to the activity-stress paradigm, and the rats that revealed hypothermia (their rectal temperature fell below 36 degrees C) were sacrificed either immediately or after several 24 h periods of healing. Rats that were sacrificed immediately after the appearance of hypothermia and those that were exposed to restricted feeding plus cessation of running revealed severe activity-stress ulcers, whereas few ulcers were observed in rats given ad lib-feeding and those that were given ad lib-feeding plus cessation of running. Although no significant differences in relative weights of spleen and thymus were obtained among the different recovery conditions, the relative weights of the adrenal glands were highest in the restricted feeding plus cessation of running group, whereas, the other animals exposed to the activity-stress paradigm showed no differences. These results indicate that activity-stress ulcers recover under conditions of ad lib-feeding within 24 h, but they are not influenced by cessation of running. These data also suggest that organ weights are not affected by any manipulations employed in the present study.

van Leeuwen, S. D, O. B. Bonne, Y. Avraham and E. M. Berry. Separation as a new animal model for self induced weight loss. Physiol Behav 62(1) 77–81, 1997.—Animal models for weight loss are generally either stress mediated or following diet restriction (DR) schedules. We investigated weight loss in mice subjected to activity stress (ACT), DR schedules of 40, 60 and 100% of daily requirements, and propose a new model for animal weight loss based upon separation. Mice were separated (SEP) from each other by perspex partitioning for 23 h per day, with free access to food for one hour. No significant differences in weight loss were found between the ACT, SEP and 40‰ groups. However, mean food intake in the 40‰ group was half that of the ACT group (p < 0.001) and significantly less (p < 0.01) than the SEP group, which consumed amounts equivalent to 65‰ of daily requirement. Separation of mice increases metabolic demands and may be used as a new, easily performed, animal model for weight loss.

Rats housed in activity wheels (A-W) or hanging cages (H-C) received food restriction to 4 h/day for 15 days. Food was given at fixed times to entrain the feeding entrainable oscillator or at irregular times to prevent entrainment. One half of the rats received food in the light phase, the other half in the dark phase of the light-dark cycle. Food was then reduced to 6 g/day for 4 days for A-W rats or 7 days for H-C rats. Stomachs were removed 24 h after the last meal and the ulcerated area was quantified. Twenty one of 32 A-W rats and 19 of 32 H-C rats had ulcers in the glandular stomach. Ulcers were significantly larger in A-W rats (p0.01). Activity levels (in A-W rats), % body weight loss and terminal body weight (in both groups) were significantly correlated with the area of ulcers. There was no significant time of day effect on the ulcer severity. However, an unexpected finding was that for A-W rats, those fed at fixed times had larger ulcers than those fed at irregular times (p0.01) while H-C rats showed an expected trend in the opposite direction. One possible explanation for this result is that for A-W rats, the reduced food supply at an expected time of day generated a greater stress response than in rats whose feeding time was unpredictable.

The present study investigated the effect of gonadal hormones on activity, food consumption, severity of ulceration, weight loss, and survival duration in male and female rats exposed to the activity-stress (A-S) paradigm. Animals received either sham surgery or gonadectomy and were housed in activity wheels or standard suspended cages. Results indicated that gonadectomized animals were more likely to engage in high running levels in the A-S paradigm; in addition, castrated males developed significantly more ulceration than the other groups. Neither sex nor gonadectomy affected the survival duration of A-S animals.

The mechanisms and applications of the activity-stress (A-S) research paradigm are examined in this article. Past research has reflected the value of this paradigm in the investigation of ulcerogenesis. Evidence is offered to support a theory explaining the excessive running observed in the A-S animals, according to which, animals commence running to increase body temperature after failing to adapt to the restricted feeding regime. Further, excessive running levels are hypothesized to be sustained by reinforcement resulting from increased mesolimbic dopaminergic activity. Finally, parallels between the behavior observed in the A-S animals and some forms of maladaptive behavior observed in humans are discussed.

The present study investigated the application of female rats with activity stress as an animal model for anorexia nervosa. Young female rats were singly housed in activity-wheel cages with food-restricted schedule (2, 3, or 4 h of food availability per day) for 3 weeks. Estrous cycle, body weight, food intake, and wheel revolution were recorded daily. Gastric pathology was also observed using the endoscopic technique. Rats that were subjected to either a 3- or 4-h feeding schedule exhibited the cessation of estrous cycle, loss of body weight, and suppression of food intake. These animals also showed a remarkable increase in running activity. However, they had no gastric lesions throughout the experimental period. On the contrary, the 2-h feeding schedule elicited severe gastric lesions and high mortality. The results suggest that behavioral and physiological changes of the young female rats with 3 or 4 h feeding share some symptoms of anorexia nervosa, although their anorexia is not self starvation.

The phenomena of activity-based anorexia (ABA) and the activity-stress ulcer (ASU) both involve paradigms in which the food intake of rats is restricted and the animals are allowed voluntary exercise in a running wheel. This study determined the susceptibility of male and female rats to ABA and ASU following 25- and 30-percent losses of their original body weights. Male rats reached both weight loss criteria in a fewer number of days than did female rats. None of the male and female rats sacrificed at the 25% weight loss criterion evidenced gastric lesions; 52% of the animals sacrificed at the 30% weight loss criterion had one or more lesions. No gender differences with respect to gastric lesions were observed at the 30% weight loss criterion; however, at both weight loss criteria, females ate and ran more than males. It is concluded that ASUs are a consequence rather than a cause of ABA, and that there is a sexually “dimorphic” susceptibility to ABA but not ASUs. The utility of using a 25% weight loss criterion for defining ABA is also discussed.

The role of prior stress experience on the response of the organism to a later stressor has been studied in terms of the extent of gastric ulceration induced by the second stressor. These studies have focused largely on effects of prior stress (shock, restraint, activity) on the ulceration developing under later restraint and activity stress. The studies indicate that prior exposure to restraint stress provides some protection against later restraint ulcer development. Using shock as the prior stressor, the effects on later restraint stress are determined by the particular characteristics of the shock (controllability and predictability), and by contextual factors. Studies are lacking on the significance of these characteristics of shock for later activity stress ulcers. Further studies are required therefore on the significance of psychological characteristics of the prestress, and on the effects of these prestressors at different stages of the life cycle. The identification of these factors, and a clearer picture of the protective and exacerbating effect of prior stress will allow us to explore the physiological (central and peripheral) mechanisms underlying ulcer development and ulcer susceptibility.

The exercising woman with nutritional deficits and related menstrual irregularities is at risk of compromising long-term bone health, i.e., the female athlete triad. There is no animal model of the female athlete triad. The purpose of this study was to examine long-term energy restriction in voluntary wheel-running female rats on estrous cycling, bone mineral content, and leptin levels. Twelve female Sprague-Dawley rats (age 34 days) were fed ad libitum and given access to running wheels during an initial 14-wk period, providing baseline and age-related data. Daily collection included dietary intake, body weight, estrous cycling, and voluntary running distance. At 4 mo, rats were randomized into two groups, six restrict-fed rats (70% of ad libitum intake) and six rats continuing as ad libitum-fed controls. Energy intake, energy expenditure, and energy availability (energy intake − energy expenditure) were calculated for each animal. Serum estradiol and leptin concentrations were measured by RIA. Femoral and tibial bone mineral density and bone mineral content (BMC) were determined by dual-energy X-ray absorptiometry. Restrict-fed rats exhibited a decrease in energy availability during Weight Loss and Anestrous phases ( P = 0.002). Compared with controls after 12 wk, restrict-fed rats showed reduced concentrations of serum estradiol ( P = 0.002) and leptin ( P = 0.002), lower ovarian weight ( P = 0.002), and decreased femoral ( P = 0.041) and tibial ( P = 0.05) BMC. Decreased energy availability resulted in anestrus and significant decreases in BMC, estrogen and leptin levels, and body weight. Finally, there is a critical level of energy availability to maintain estrous cycling.

This review provides a discussion of the pathophysiologic significance of animal models of the activity-stress paradigm and the role of plasma glucose level in the appearance of physical stress responses of those models. Many research reports have demonstrated that animal models exposed to activity-stress are useful as a “symptomatic model” of anorexia nervosa and obsessive-compulsive disorder as well as peptic ulcer. Our findings show that a decrease in plasma glucose concentration is an important factor in determining the activity-stress-induced physical responses. Further investigation of the pathophysiology of activity-stressed animal models may contribute to the development of new therapeutics for diseases such as anorexia nervosa and obsessive-compulsive disorder.

Two methods of monitoring the circadian rhythm of activity in rodents: (1) an activity wheel cage, which detects the number of wheel revolutions, and (2) an internal radio transmitter, which records gross motor activity (GMA) of the animal, were compared in both normal circadian cycles and during the development of activity-stress ulcers. Rats were implanted with a biotelemetry transmitter that detected GMA and body temperature (BT) and placed in activity wheel cages. A 12 hour/12 hour light/dark cycle was maintained throughout the experiment. Subjects were subdivided into two groups: (1) unlimited access to activity wheel (AW) cages and (2) locked activity wheel (LW) cages. Following an ad-libitum habituation period, animals were allowed food access for 1 hour/day during the light. In the habituation period, the animals showed higher GMA and BT during the dark phase when housed in AW cages than in LW cages. Both GMA and number of wheel revolutions increased dramatically after the onset of food restriction for the AW animals. There was a deleterious drop in BT in AW animals as the food-restricted period continued and a significant correlation existed between severity of ulcerations and BT. The findings of this experiment demonstrate that the activity wheel imposes an alternation of the circadian cycle, which, in turn, influences rhythmicity through reentrainment. Additionally, in the activity-stress paradigm, a significant drop in BT correlates with severity of ulcerations. A disrupted circadian cycle, involving hypothermia, is proposed as the mechanism underlying the demise of animals in the activity-stress paradigm.

The relationship between restricted feeding, core body temperature (Tb), wheel running, survival, and gastric erosion formation was examined in female rats exposed to activity-stress. Core body temperature and gross motor activity were telemetrically monitored in four groups of rats that had free access to running wheels and in one group that was not allowed to run on the wheels. Twenty-four hours prior to the onset of hypothermia and predicted mortality, different groups were left undisturbed, warmed with a heat lamp, denied access to running wheels, or euthanized. Length of survival in wheel-running rats varied from 2 to 12 days. During the first day of food deprivation, premorbid changes in the variability of Tb during the diurnal period and the mean number of wheel revolutions during the nocturnal period were strongly predictive of length of survival. Warming rats with a heat lamp or preventing rats from ever running on the wheel increased the length of survival and attenuated gastric erosion formation. Only rats that were warmed had a greater likelihood of survival. Gastric pathology was also reduced in rats that were euthanized prior to becoming moribund. Rats that were left undisturbed or locked from the running wheel over the last 24 h of testing became moribund and had extensive gastric mucosal damage. These results indicate that thermoregulatory disturbances induced by restricted feeding and not wheel running alone are critical in determining survival and the degree of gastric mucosal injury in rats exposed to activity-stress. Results further suggest that predisposing factors may put some rats at risk for the development of activity-stress-induced mortality.

In the present study, 28 pregnant rats were subjected to either light-restraint stress or no manipulation for days 14–21 of the gestational period. At approx. 50 days of age, both male (n = 16) and female (n = 16) prenatally stressed (PS) and control offspring were subjected to the activity stress (AS) paradigm. During this subsequent stress experience, PS rats developed less ulceration than control rats. PS rats also displayed about half the activity of the control animals during the habituation phase of the AS paradigm, prior to the induction of stress. Given this decrease in baseline activity in PS animals, implications of using activity as a measure of emotionality in PS animals are discussed. Several sex differences were also observed; females differed from males in that they 1) exhibited higher activity levels in both the habituation and experimental phases of the AS procedure, 2) developed heavier relative adrenal weights, and 3) reached criteria for sacrifice in fewer days.

To examine the role of the amygdala in the production of gastric ulcers induced by activity-stress, electrolytic lesions were placed in the centromedial (CENT) and medial (MED) amygdaloid nuclei, as well as in the intra-amygdaloid division of the bed nucleus of the stria terminalis (BNST). As compared to sham-operated controls (CONT), gastric ulceration was attenuated in rats with CENT lesions and exacerbated in rats with lesions located in the BNST or MED. Wheel running did not differ significantly between control animals and lesioned rats, but did differ within lesioned groups. Rats with MED lesions ran more than rats with CENT or BNST lesions. Results support the view that the integrity of the centromedial amygdala is critical for the maintenance of the viscera and demonstrate that neurogenic factors contribute to the development of gastric erosions during exposure to activity-stress.

The relationship between gastric injury and wheel running was examined during an activity-stress (A-S) experiment. In Experiment 1, rats were preadapted to a 1-h restricted feeding schedule for either 0, 15, 25 or 35 days prior to entering activity wheels. All rats preadapted to the 1-h feeding schedule had significantly less gastric damage than rats without any preadaptation experience. Survival of A-S was related to the length of preadaptation experience. Regardless of preadaptation experience, rats increased daily running with the greatest increase occurring during the 6-h period preceding the feeding hour. In Experiment 2, rats were injected twice daily with cimetidine (100 mg, ip) or vehicle during the 6-h preceding the feeding session. Rats treated with cimetidine had less mucosal injury but had no increased survival when compared to rats injected with the vehicle. Cimetidine treated rats had essentially the same running pattern as controls. These results demonstrated that the process of mucosal injury did not stimulate excessive wheel running. The data also suggest that mucosal injury is not related to survival in A-S rats.

The present study investigated the role of dopamine in the maintenance of behaviors observed in the activity-stress paradigm. In Experiment 1, several doses (0, 0.125, 0.25, 0.50, and 1.0 mg/kg) of the dopamine D2-receptor blocker, pimozide, were administered to rats maintained on an ad lib feeding schedule. Results indicated that 0.25 mg/kg pimozide did not disrupt running activity when compared to control animals. In Experiment 2, injections of either 0, 0.25, or 0.50 mg/kg pimozide were given every 12 hours to rats subjected to the activity-stress paradigm. Although 0.25 mg/kg pimozide had no effect on dark-phase activity, it significantly suppressed light-phase activity and subsequently increased the number of survivors in the paradigm. It was concluded that dopamine plays a role in maintaining high running levels in the activity-stress paradigm.

The present study investigates the effects of truncal vagotomy and drug treatment, comprising atropine methylbromide and chlorisondamine, on the development of activity-stress ulcers in rats. To induce gastric lesions, female rats were housed individually in activity-wheel cages and subjected to a food-restricted schedule of only 1 hr food availability per day. Bilateral truncal vagotomy significantly prevented gastric ulceration, while those rats with vagotomy showed more running activity than sham-operated rats. Daily treatment with either methylatropine (3 and 6 mg/kg, s.c.) or chlorisondamine (2 and 4 mg/kg, i.p.) also significantly decreased the severity of lesions without a significant reduction in running activity. This evidence suggests that the development of activity-stress ulcers is mainly due to the hyperactivity of the peripheral parasympathetic nervous system.

Chipmunks were allowed access to a running wheel and fed 1½ h each day. After 13 days of restricted feeding, all activity animals had died and postmortem pathology revealed extensive lesions of the glandular stomach. Food-yoked control animals, not allowed to exercise, very rarely died and showed minimal signs of stomach pathology when autopsied. Circadian running patterns of activity animals indicated a marked increase in diurnal running during restricted feeding. Results indicate that the activity-stress procedure is capable of producing stomach ulcers in a wild animal species.

Rats were given d-amphetamine alone, placebo or d-amphetamine and food. They were then placed in the activity-stress ulcer paradigm, involving continuous access to a running wheel while being fed for only 1 hr. per day. Animals given d-amphetamine only ran more and died significantly sooner than animals in any other group. These rats also displayed significantly more gastric glandular ulcers than rats in any other group. Rats given d-amphetamine and food exhibited increased running but did not die sooner and displayed ulceration comparable to placebo rats. It appears that neither restricted feeding nor increased running wheel activity is a sufficient cause of activity-stress ulcers; rather, the combined interaction. of both of these variables appears to produce the observed gastric damage.

The activity-stress ulcer procedure consists of housing rats in running-wheel activity cages while at the same time, restricting their food intake to 1 hr per day. Male Wistar rats which had been habituated with ad lib feeding to the running-wheel cage environment for 3 days prior to the restricted feeding phase, developed significantly more gastric glandular ulcers and exhibited greater levels of running activity when compared to rats which had been given no habituation experience. Control rats housed in standard laboratory cages but which received the same restricted feeding regimen, developed significantly less stress pathology. Since allowing to rats access to the running-wheel during habituation resulted in enhanced stress pathology, this manipulation is referred to as a “priming effect.” A possible explanation for such a “priming effect” is discussed in terms of procedures which may increase running wheel activity and decrease survival time during the restricted feeding phase of the activity-stress ulcer procedure.

Male Wistar rats were exposed to a 5-day activity-stress procedure wherein animals were housed in running-wheel activity cages and fed for only 1 hr each day (wheel-housed/food-restricted rats). This activity-stress procedure produced marked elevation in levels of the major metabolite of noradrenaline (NA), 3-methoxy-4-hydroxyphenylethyleneglycol sulfate (MHPG-SO4), in eight brain regions, while a reduction of NA level occurred in several of these brain regions. These rats also exhibited excessive running activity and developed severe gastric glandular ulcers. Rats fed ad lib and housed in activity cages (wheel-housed/ad lib-fed) and rats housed in standard-individual cages and which received either 1-hr daily feeding (control cage-housed/food-restricted) or ad lib feeding (control cage-housed/ad lib-fed) showed neither significant changes in brain NA metabolism nor gastric ulcers. These results suggest that the interaction of a restricted feeding regimen and an increase running wheel activity caused marked enhancement of NA turnover in several brain regions, which is one of the neurochemical mechanisms underlying the physiological and behavioral changes produced by the activity-stress paradigm.

Rats housed in running wheel activity cages except for 1 hr each day, during which time they were fed in their home cages, revealed more stomach ulceration, a higher level of brain MHPG-SO4, and larger weight changes in the thymus, spleen and adrenal gland, compared to rats housed in running-wheel activity cages and fed 1 hr daily in those same cages. Rats in the latter group showed more stress pathology than did control rats which were housed in standard home cages but which received the same restricted (1 hr per day) feeding schedule. These results did not support the idea that excessive running might occur in response to certain motivational states (e.g., frustration due to restricted feeding). The data suggested that feeding activity-stress rats in their home cages might aggravate the development of stomach ulcers coincident with the organ weight changes and the enhancement of noradrenaline turnover in the brain.

In Experiment 1 the number and size of ulcers resulting from exposure to an activity-stress procedure were inversely related to the length of the pre-stress experience with either 1 hr or 2 hr daily feeding schedules. In Experiment 2, rats housed in group cages during the pre-stress period were more vulnerable to the ulcerogenic effects of the activity-stress procedure. A pellet food or powdered food treatment condition failed to provide significant group differences. Vulnerability to stress-ulcer is discussed in terms of the disparity of the environmental conditions between the acclimation period and the activity-stress period.

Rats were divided into either an active group housed in activity wheels or a control group housed in stationary laboratory cages. Both active and control groups were further divided into groups receiving 1, 2, 3, or 4 meals daily for a total feeding time of 1 hr. Control rats were food-yoked to active animals. Results indicated that active rats fed 1 meal daily developed significantly more ulceration, lost more weight, and consumed less food and water than other groups. The number of daily meals had no effect on the amount of activity. No control animals developed ulcers, although they received the same amount of food. These results suggest that frequent feedings mitigate gastric peptic ulcer formation in rats placed in the activity-stress ulcer paradigm.

Spontaneously hypertensive rats (SHR), Wistar Kyoto (WKY) and Wistar rats were exposed to Porsolt's forced-swimming test of “behavioral despair.” In addition to floating time, which was the measure of despair, headshakes, bobbing, diving and struggling time were also recorded. Rats were subsequently exposed to the activity stress (A-S) ulcer procedure. Wistar rats had the highest struggling time scores and the fewest A-S ulcers. WKY rats were judged as more depressed and their ulcer severity scores were significantly greater as compared to SHR and Wistar rats. In addition, a within strains analysis revealed that WKY rats with high despair scores also had the most severe stress-ulcer scores. These data suggested that stress-ulcer disease may be more prevalent in animals which are prone to depression as defined by the Porsolt test. The value of WKY rats as an animal model to study the relationship between depression and stress ulcer is discussed.

Rats were either group-housed, four rats per cage, or housed singly for 6 weeks. Subgroups were subsequently exposed to a daily 3-min 1.25-mA grid shock for 5 days. The rats were then housed in running-wheel activity cages and, following a 4-day free-feeding period, were fed only 1 h daily for 20 days. Group-housed rats had more ulcers, but the previously reported protective effect of preshock was not observed in this study.

Rats were housed in standard activity cages under normal LD cycle (lights on 7:00–19:00) and fed 1 hr each day for 2 weeks. Control rats which were fed 1 hr each day in laboratory cages or fed freely in activity cages did not die and were ulcer-free. Incidence of rats with ulcer was higher in the group fed 1 hr in the nighttime than in the daytime group fed 1 hr in the morning, whereas the mortality was similar for both groups. The daytime group died sooner than the nighttime group. Thymus and spleen weights of rats exposed to activity-stress decreased considerably, while adrenal weights increased. The victims always revealed pulmonary infection, and the microscopic pathology of the thymus and spleen disclosed the lack of immunologically competent cells. Accordingly, these results suggest that rats exposed to activity-stress reveal, not only ulceration, but also immunosuppression. Stress factors and the possibility of utilizing the activity-stress rat for an immunodeficiency model are discussed.

Knudsen, O. National Interests and Foreign Policy: On the National Pursuit of Material Interests. Cooperation and Conflict, XIV, 1979, 11-19. The classical concept of 'the national interest' is not at issue here. Rather, an attempt is made to systematize some quite simple and familiar ideas about 'what is to the material advantage' of a state in given situations of choice. The basic argument is that most current explanations of foreign-policy activity stress bureaucratic/administrative factors and overlook the possible significance of the material benefits at stake. 'National interests', in this usage, are the prospective national gains or losses in a concrete decisional situation. The article sets out the outline of a procedure by which objective estimates (i.e. based on the analyst's systematic criteria rather than the participant's own evaluations) of material advantage may be made. Examples of such studies are given. The last part of the article raises the question of what can and cannot be explained by this approach, and compares it with reasoning based on interest groups and decision-making factors. The conclusion emphasizes that our knowledge of the true significance of interest groups and decision-making factors is very limited as long as such models are not tested against the predictions of a 'national-interest model'.

Rats were exposed to daily sessions of either restraint plus cold, forced exercise, or grid shock for one month and then subjected to the ulcerogenic effects of either supine restraint plus cold, or activity-stress. Chronic stress generally protected against stress ulcer but the protection depended on the degree of similarity between the pre-treatment stressor and the ulcerogenic procedure. Pre-treatment with restraint plus cold provided protection which applied not only to supine restraint plus cold but also generalized to activity-stress. Foot-shock pre-treatment did not significantly reduce restraint ulcer but it significantly exacerbated activity-stress ulcer.

Rats housed in activity cages and fed 1 hour daily died before the end of the 21-day experimental period and revealed extensive ulcers in the glandular stomach, whereas food-yoked control rats, not housed in activity cages, did not die and were ulcer-free. Rats demonstrating high running-activity levels under ad lib feeding conditions subsequently revealed a higher incidence of lesions as compared to low-activity rats. Attempts to attenuate activity and lesion incidence by reversing the light-dark cycle failed, but the higher mortality level in rats under the reversed light-dark condition was related to higher activity levels in these rats. Young rats with high activity levels died sooner and had ulcers when compared to older rats with low activity levels. These results suggested that running activity, and not reduced food intake, was critically involved in the development of the activity-stress ulcer.

In order to examine the susceptibility of Brattleboro rats to self-starvation and activity stress, as evidenced by ulcer formation, four conditions were studied: (1) ad-lib access to food and water in an individual home cage, (2) ad-lib access to food and water in an activity-wheel cage, (3) ad-lib access to water and 1-h access to food in an individual home cage, and (4) ad-lib access to water and 1-h access to food each day in an activity-wheel cage. In the first two conditions, neither Brattleboro nor control animals developed ulcers. In the third condition, some rats in each group developed pits in the glandular portion of the stomach. Significant differences appeared in the fourth condition. Brattleboro rats developed more stomach pathology in both the nonglandular and glandular portions of the stomach than controls. The results were not due to variations in running behavior. The data indicate that the lack of vasopressin or physiological results of this deficit render Brattleboro rats more sensitive to self-starvation and activity stress than control animals.

Rats housed in running-wheel activity cages and fed 1 h daily exhibited excessive running and subsequently died revealing large stomach ulcers. However, prior experience with a 1-h feeding schedule for 15 days before exposure to the activity-stress procedure did significantly extend survival time. A second study illustrated that feeding schedules of.5, 1.0, 1.5, or 2.0 h daily did not yield differences in terms of stomach ulcers or survival time, but a 3-h daily feeding did significantly reduce ulcer incidence and increase survival time.

The present study was designed to investigate the relationship between activity stress, alcohol consumption and ulcer proliferation. Ethanol consuming rats were initially divided into low, medium or high ethanol preferring groups on the basis of daily ethanol intake (g/kg/day). Following a habituation period in activity cages, animals were fed for 1 hr per day. Access to both water and ethanol remained ad lib. Yoked control home cage animals were fed the same amount of food consumed by their wheel-housed partners. This procedure continued until wheel-housed animals died, at which time thwy and their yoked home cage control partners were examined for ulcers. Results indicated that in contrast to the yoked controls, only the high ethanol-preferring rats reduced their ethanol consuption. Although no differences were apparent in ulcer frequency (mean number of ulcers per rat) or severity (mean cumulative ulcer length in millimeters), animals exposed to ethanol had a lower ulcer incidence (number of rats per group developing ulcers) and mortality rate than non-ethanol exposed animals.

Rats sacrificed after 4 days in the activity-stress paradigm or after 4 days of food restriction had significantly elevated levels of plasma corticosterone as compared to control rats. The approximately 5 fold increase in corticosterone in the stressed treatment groups was consistently found in all experiments. ACTH levels were elevated in activity-stress and food-restricted groups in some experiments but these increases were not statistically significant. Prolactin levels were significantly elevated in food-restricted group rats as compared to controls or activity-stress group animals in one experiment but this finding was not repeated in further experiments. In a second series of experiments, rats from activity-stressed and food-restricted treatment groups and controls were exposed to an acute stressor for 15 min prior to sacrifice to assess the effects of prior sustained stress on hormonal responses to an acute stressor. Exposure to 15 min of immobilization or intermittent footshock immediately prior to sacrifice increased plasma levels of corticosterone, ACTH and prolactin in control, foodrestricted and activity-stressed rats. Generally, hormonal responses to the acute stress were similar in all treatment groups. However, in two experiments where the resting levels of corticosterone were especially elevated in the activity-stress group, the acute stress-induced rise in corticosterone was less than that seen for the other two treatment groups. In another experiment, administration of dexamethasone suppressed acute stress-evoked levels of ACTH and corticosterone in control, activity-stressed and food-restricted rats. Thus, rats exposed to 4 days of sustained stress were found to have consistently elevated resting levels of corticosterone. Hormonal responses to acute stress or dexamethasone administration, however, were generally similar in activity-stressed, food-restricted and control rats.