Stress-exposed Groups Research Articles

Protective Effects of Tualang Honey on the Testes of Rats Subjected to Chronic Combined Stress

Introduction: Persistent exposure to stress can lead to a wide range of pathological effects, including reproductive dysfunctions. Tualang honey, renowned for its antioxidant properties has been utilised in traditional and modern medicine. This study aims to investigate the protective effects of Tualang honey against stress-induced testicular damage in male rats. Method: Twenty-four male rats were divided into control group, stress-exposed group, Tualang-honey-supplemented group and stress-exposed with Tualang-honey-supplemented group. Restraint stress test (RST) and Forced swimming test (FST) were imposed on the rats for 21 days. Serum testosterone and corticosterone concentration were measured using ELISA. Testes were harvested, weighed, processed and stained for spermatid counts and measuring seminiferous epithelial height and diameter. One-way analysis of variance (ANOVA) was used to compare the numerical data between groups. Results: The testosterone concentration, spermatid count, seminiferous epithelial height and diameter in stress group were significantly lower compared to control group (p < 0.05). Corticosterone concentration was significantly greater in the stress group than in the control group. The spermatid count and seminiferous epithelial height and diameter of honey-treated groups were significantly higher than the stress-only group (p < 0.05). The corticosterone concentration of honey-treated groups was significantly higher compared to the stress-only group. Meanwhile, the testosterone concentration of honey-treated groups was higher than the stress-only group although the results were insignificant. Conclusion: Tualang honey has the potential to ameliorate corticosterone concentration and induce morphological alterations by increasing spermatid counts and seminiferous epithelial thickness and diameter in rat testes exposed to prolonged stress.

The effect of MK-801 on stress-ethanol cross-sensitization is dissociable from its effects on nNOS activity.

Locomotor behavioral sensitization represents an animal model for understanding neuroadaptive processes related to repeated drug exposure. Repeated stress can elicit a cross-sensitization to the stimulant response of ethanol, which involves neuronal nitric oxide synthase (nNOS). Activation of N-methyl d-aspartate (NMDA) glutamate receptors triggers nNOS and the synthesis of nitric oxide (NO). In this study, we investigated the effects of blocking NMDA receptors using the NMDA receptor antagonist MK-801 on the cross-sensitization between restraint stress and ethanol. We also evaluated the nNOS activity in the prefrontal cortex (PFC) and hippocampus. Mice were pretreated with saline or MK-801 30min before an injection of saline or stress exposure for 14 days. On the following day, they were challenged with either saline or 1.8g/kg ethanol. Swiss male mice pretreated with 0.25mg/kg MK-801 exhibited a sensitized response to ethanol. Moreover, MK-801 potentiated the cross-sensitization between stress and ethanol. However, MK-801 prevented the enhanced nNOS activity in stress-exposed groups (challenged with saline or ethanol) in the PFC; the antagonist also prevented the ethanol-induced increase in nNOS activity and reduced this enzyme activity in mice exposed to stress in the hippocampus. These data indicate that systemic treatment with the NMDA antagonist potentiated, rather than blocked, ethanol-induced behavioral sensitization and that this effect is dissociable from the capacity of NMDA antagonists to reduce ethanol/stress-induced NOS stimulation in the PFC and hippocampus.

Changes in weight gain, digestive and metabolic enzymeactivities in Labeo rohita fingerlings in response to multiple stress exposure and dietary nutraceutical.

A feeding trial was conducted for 4months to study the effect of a nutraceutical conglomerate at different levels (0, 0.1, and 0.5%) on stress-exposed (high stocking density, H and feed restriction, R) Labeo rohita fingerlings. Six isonitrogenous diets with a crude protein of 35% were prepared for the different treatments, viz. THR0, THR1, THR5, TNS0, TNS1 and TNS5. Stress significantly reduced the weight gain and feeding of 0.1% nutraceutical improved it in both stress-exposed and non-exposed groups from 3months onwards. Two-and three-month stress-exposed groups exhibited lower (p < 0.05) protease activity, while amylase activity was significantly higher in 2-month stress-exposed groups. Higher lipase activity was found in stress-exposed groups irrespective of theduration of stress. Higher serum glutathione peroxidase (GPx), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and hepatic and muscle lactate dehydrogenase (LDH) activities were observed in the THR0 groups; however, THR1 showed a lower activity of these enzymes. Increased malate dehydrogenase (MDH) and glucose-6-phosphate dehydrogenase (G6PDH) activity was recorded in the 1st and 2nd months stress-exposed groups.However, THR1 group exhibited a reduced MDH and G6PDH activity compared to THR0 group in 1st and 2nd months.Hence, it can be concluded that the duration of multiple stress exposure adversely affected the digestive and metabolic enzymesactivities and feeding of 0.1% nutraceutical conglomerates could restore the activities of digestive and metabolic enzymes in rohu fingerlings.

Prenatally stress-exposed male rats present lower theta prefrontal activity during attention behaviors to receptive females

Prenatal stress affects brain functionality and sexual behavior. The medial prefrontal cortex (mPFC) participates in the integration and processing of sexual stimuli. Electroencephalographic (EEG) theta activity has been associated with attention as well as rewarding and sexually motivated states. Considering that the induction of sexual motivation requires attention to, and the adequate processing of, sexual stimuli, this study aimed to evaluate the effects of exposure to stress during the prenatal period on EEG activity in the mPFC during nose pokes in adulthood, actions which are indicators of attention to a receptive female. Eighteen sexually experienced male rats were used, nine stressed prenatally by immobilization during days 14–21 of gestation (stress-exposed group). The other nine formed the control group. All rats were implanted bilaterally in the mPFC (specifically in prelimbic areas) and were allowed one intromission with a receptive female to induce a sexually motivated state before the experimental session. During this session, both nose pokes and non-contact erections in the male rats were evaluated in the presence of an inaccessible receptive female. EEGs were recorded only during nose pokes. The stress-exposed group presented lower nose poke duration, fewer non-contact erections, and lower relative power of the theta band (4–7 Hz) in both prefrontal areas. Considering that the prevalence of this band is associated with attention and motivational processes, these data confirm the deleterious effect of prenatal stress on attention and sexual activation to sexually relevant stimuli in male rats during adulthood.

Repeated exposure to challenging environmental conditions influences telomere dynamics across adult life as predicted by changes in mortality risk.

The effects of stress exposure are likely to vary depending on life-stage and stressor. While it has been postulated that mild stress exposure may have beneficial effects, the duration of such effects and the underlying mechanisms are unclear. While the long-term effects of early-life stress are relatively well studied, we know much less about the effects of exposure in adulthood since the early- and adult-life environments are often similar. We previously reported that repeated experimental exposure to a relatively mild stressor in female zebra finches, first experienced in young adulthood, initially had no effect on mortality risk, reduced mortality in middle age, but the apparently beneficial effects disappeared in old age. We show here that this is underpinned by differences between the control and stress-exposed group in the pattern of telomere change, with stress-exposed birds showing reduced telomere loss in middle adulthood. We thereby provide novel experimental evidence that telomere dynamics play a key role linking stress resilience and aging.

Effects of the moderate stress exposure on the short-term memory capacity: An experimental study in fire cadets

IntroductionFuture firefighters are selected and trained to perform well under pressure and stress.ObjectivesThe research is focused on the experimental study of fire cadets’ memory capacity under stress.MethodsThe study follows Solomon Four Group Design with two variables: stress stimuli (exposure/non-exposure), fire cadets (n=50)/civilian students (n=40). Two series of The Digit Span Test measurements (DST) were performed. Heart rate, EMG, systolic wave amplitude, pulse transit time were measured during the experiment to determine the respondents’ stress levels.ResultsMemory capacity in fire cadets under stress (n=30) significantly increased (Wilcoxon match-pairs rank test, р = 0.001; 1st DST series, neutral stimuli: M=6.53, SE=0.17, SD=0.96; 2st DST series, stressful stimuli: M=7.3, SE=0.21, SD=1.16), the obtained effect size was medium (Cohen’s d = 0.7232). There was no significant change in memory capacity in civilian students under stress (n=20, Wilcoxon test, р=0.452; 1st DST series, neutral stimuli: M=6.78, SE=0.23, SD=1.02; 2st DST series, stressful stimuli: M=6.7, SE=0.23, SD=1.04). Moreover, there was no significant change in memory capacity in fire cadets that were not under stress (n=20, Wilcoxon test, р = 0.628; 1st DST series, neutral stimuli: M=6.88, SE=0.16, SD=0.70; 2st DST series, neutral stimuli: M=6.78, SE=0.16, SD=0.73). Systolic wave amplitude in the stress-exposed groups changed more pronouncedly in students (Mann–Whitney test, z=-2.131; p = 0.033) compared to cadets.ConclusionsIn most of the fire cadets, moderate stress exposure resulted in a memory capacity increase.DisclosureNo significant relationships.

Heat Induces Oxidative Stress: Reproductive Organ Weights and Serum Metabolite Profile, Testes Structure, and Function Impairment in Male Cavy (Cavia porcellus).

The present study was designed to evaluate the effects of heat that induces oxidative stress on reproduction organ weight and serum biochemical, testes structure, and function in male guinea pig (Cavia porcellus). Forty-eight male guinea pigs with an average weight of 330.56 ± 23.62 g, aged 3–4 months, were distributed into four groups of 12 animals each. One group (control) was maintained to ambient temperature (20–25°C), while other groups (Groups 2–4) were exposed daily for 6 h, to 32 ± 1°C, 39±1°C, and 46 ± 1°C, respectively. All animals were sacrificed after 60 days' exposure and their reproductive characteristics values were determined. Results revealed a significant decrease (p < 0.05) of the weight of testes, epididymis, vas deferens, and accessory glands in cavies exposed to the highest temperature investigated (46 ± 1°C), compared to the control animals. There was a significant (p < 0.05) reduction of serum testosterone and LH levels in all heat stress-exposed groups (≥46 ± 1°C) when compared to the control group. Heat stress significantly (p < 0.05) decreased sperm mobility, sperm count, and testicular antioxidant enzymes, while increasing testicular malondialdehyde content. However, the serum level of HSP-40 increased in the animals exposed to 39 ± 1°C and decreased when the cavies were exposed to 46 ± 1°C. In conclusion, exposure to heat-induced oxidative stress results in impairment of reproduction organ weight and serum biochemical, testes structure, and function in male cavies.

Holocaust history is not reflected in telomere homeostasis in survivors and their offspring

Telomeres, nucleoprotein structures at the ends of eukaryotic chromosomes, are crucial for the maintenance of genome integrity. While the lengths of telomeres at birth are determined genetically, many factors including environmental and living conditions affect the telomere lengths during a lifespan. In this context, extreme and long-term stress has been shown to negatively impact telomeres and their protective function, with even offspring being influenced by the stress experienced by parents. Using quantitative PCR, the relative lengths of telomeres of survivors of the Holocaust during World War II and two generations of their offspring were analyzed. These data were related to those of control groups, persons of comparable age without a strong life stress experience. In contrast to previous studies of other stress-exposed groups, the relative lengths of telomeres were comparable in groups of persons exposed to Holocaust-related stress and their progenies, and in control groups. Interestingly, shorter telomeres of Holocaust survivors of the age under 12 in the year 1945 compared to Holocaust survivors of the age above 12 were detected. Our results are discussed with respect to certain exceptionality of persons having been able to cope with an extreme stress more than 70 years ago and living to a very old age.

EFFECTS OF MUSIC AND STRESS ON HEALING OF INDUCED WOUND IN THE SKIN OF ADULT MALE ALBINO RATS

Background: Wound healing is a complex process involving intrinsic dermal and epidermal cells, and infiltrating macrophages and leukocytes.Noise and music exposure have long been used to investigate their effects on biological and biochemical responses. Objectives: Studyingthe possible acceleration effect of the process of wound healing after exposure to music, and the stressor effect after exposure to noise. Materials and Methods: Forty adult male albino rats of local strain were chosen as an animal model for this study. They were divided into four equal groups:Control group, wound group, stress-exposed group andmusic-exposed group. On the day of infection, superficial surgical wounds were produced on the shaved backs of anesthetized rats by making a longitudinal midline incision, 2.3 ± 0.2 cm in length and extending down to the panniculuscarnosus.At the end of the experiment (30 days), blood samples were obtained for estimation of WBC, neutrophils, lymphocytes and platelets count. Immediately after the animals were killed, 5-mm punch biopsy specimens of excised skin were taken, and immediately fixed in phosphate-buffered (pH 7.4) formalin (4%). Results: Stress- exposed group showed significant increase in both WBCs and neutrophils counts, and significant decrease in both lymphocytes and platelets counts. In music-exposed group, WBCs significantly increased and platelets significantly decreased. Histopathological examination revealed that the exposure to noise resulted in significantly slowed inflammatory process. This effect was demonstrated by increased infiltration of wounds with polymorphnuclear leucocytes (PMNL). The music exhibited significant acceleration of wound healing activity as compared to noise exposed group .The wound closure time was lesser, as well as the percentage of wound contraction was more. The epithelization of wound was found to be earlier as compared tonoise exposed group. Conclusion: Music has some antistressor effects and may accelerate wound healing.

Effect of agomelatine on adult hippocampus apoptosis and neurogenesis using the stress model of rats

Agomelatine (AG) is an agonist of melatonin receptors and an antagonist of the 5-HT2C-receptor subtype. The chronobiotic properties of AG are of significant interest due to the disorganization of internal rhythms, which might play a role in the pathophysiology of depression. The present study was designed to assess the effects of the antidepressant-like activity of AG, a new antidepressant drug, on adult neurogenesis and apoptosis using stress-exposed rat brains. Over the period of 1 week, the rats were exposed to light stress twice a day for 1h. After a period of 1 week, the rats were given AG treatment at a dose of either 10mg/kg or 40mg/kg for 15 days. The animals were then scarified, and the obtained tissue sections were stained with immuno-histochemical anti-BrdU, Caspase-3, and Bcl-2 antibodies. Serum brain-derived neurotrophic factor (BDNF) concentrations were measured biochemically using a BDNF Elisa kit. Biochemical BDNF analysis revealed a high concentration of BDNF in the serum of the stress-exposed group, but the concentrations of BDNF were much lower those of the AG-treated groups. Immuno-histochemical analysis revealed that AG treatment decreased the BrdU-positive and Bcl-2-positive cell densities and increased the Caspase-3-positive cell density in the hippocampus of stress-induced rats as compared to those of the stress group. The results of the study demonstrated that AG treatment ameliorated the hippocampal apoptotic cells and increased hippocampal neurogenesis. These results also strengthen the possible relationship between depression and adult neurogenesis, which must be studied further.

Effects of 15-day chronic stress on behavior and neurological changes in the hippocampus of ICR mice

Numerous rodent models of depression have been reported, most requiring a long experimental period and significant effort. We explored a new potential mouse model for depression by investigating whether exposure to a 15-day chronic stress paradigm could induce depression-like behavior in ICR mice. Animals in the stress-exposed groups were subjected to 3 h of restraint while immersed in a 28°C water bath daily for 15 consecutive days. Immobility time in the forced swim test was increased in the chronic stress-exposed mice compared with the controls. Serum corticosterone levels were also much higher in the stressed mice than in the control mice. Hippocampal cell survival (BrdU-positive cells) and neurotrophic factor (NGF, TrkA) mRNA levels were significantly decreased in the chronic stress-exposed mice compared with controls. Administration of the anti-depressant drugs clomipramine (20 mg/kg/d) or imipramine (30 mg/kg/d) did not change the immobility time in the forced swim test, but treatment with lithium (100 mg/kg/d) did result in slight improvement. These results suggest that this 15-day chronic stress paradigm can induce depression-like behavior and neurological changes, in a short time and with minimal effort, facilitating the assessment of treatments for depression.

Elevated hair cortisol levels in chronically stressed dementia caregivers.

Hair cortisol concentrations (HCC) are assumed to reflect integrated long-term cortisol levels and have been proposed as a promising endocrine marker of chronic psychological stress. The current study examined HCC in relation to caregiving burden, a well-established naturalistic model of chronic stress in humans. HCC and relevant psychosocial data were examined in 20 caregivers of relatives with dementia and 20 non-caregiver controls matched for age and sex. Results revealed elevated HCC in dementia caregivers compared to non-caregiver controls (F(1,38)=4.4, p=.04, ηp2=.10). Further, within caregivers, a trend for a positive association of HCC with self-reported caregiving burden (r=.43, p=.058) and a positive association with depressiveness (r=.48, p=.045) were observed. No other associations between HCC and subjective measures were seen. These findings concur with the notion that HCC sensitively capture endocrine aberrations in stress-exposed groups.

Stress-Induced Changes in Testosterone Secretion in Male Rats: Role of Oxidative Stress and Modulation by Antioxidants

Seventy adult male albino rats were randomly allotted into 3 main groups: control group (n = 10), acute stress-exposed group (n = 30) and chronic stress-exposed group (n = 30). Each of the stressed groups was subdivided into 3 equal subgroups (n = 10/subgroup, SG): subgroup 1 animals were exposed to immobilization stress, SG2 animals, were given immobilization stress and supplemented with α-tocopherol (vitamin E), SG3 animals were exposed to immobilization stress and supplemented with ascorbic acid (vitamin C). Immobilization stress exposure was applied once for 6 continuous hours in the acute stressed group and was 6 hours daily for 10 consecutive days in the chronic stressed group. In all vitamin supplemented groups, both vitamin E and C were administered orally mixed with the diet in a similar dose of 500 mg/kg diet. This supplementation started 6 weeks prior to the stress exposure and continued throughout the experimental period. At the end of the last immobilization session, sera were harvested from all animals thereafter, animals were sacrificed and the testes were immediately excised and processed for further biochemical investigations. Serum testosterone and luteinizing hormone levels were measured and the activities of antioxidant enzymes [catalase (CAT) & glutathione-s-transferase (GST)] as well as malondialdehyde (MDA) concentrations were determined in sera and testes. Compared to control, the results revealed that acute and chronic immobilization stress caused significant decrease in levels of serum testosterone and luteinizing hormone (LH). Also, significant reductions (P < 0.01) were found in the activities of CAT and GST in sera and testes. Contrariwise, there existed a significant (P < 0.05) increase in MDA concentrations in serum and testis. Co-administration of vitamin E or C relatively restored (P < 0.01) the above parameters. Thus, this study draws a conclusion that immobilization stress of male rats significantly inhibited testosterone secretion and induced oxidative stress which partially mediated this inhibition. It also proved a protective role of vitamin E and C against the oxidative stress-induced down-regulation of testosterone secretion with a better efficacy of vitamin E.

Physiological responses of dietary tryptophan fedLabeo rohitato temperature and salinity stress

Two experiments were conducted to elucidate the possible effects of dietary L-tryptophan (TRP) in Labeo rohita based on growth performance and physio-biochemical responses. In the experiment I, a 60-day feeding trial was carried out to elucidate the effects of dietary TRP enrichment on growth performance and physio-biochemical responses. In the experiment II, the TRP pre-fed L.rohita, from experiment I, was exposed to temperature and salinity stress to evaluate stress-mitigating efficacy of TRP. In L.rohita, dietary supplementation of TRP showed significant effect on weight gain percentage and feed conversion ratio but not on blood glucose. A significant increase in RNA content and RNA/DNA ratio upon TRP supplementation was observed and was positively correlated with growth performance. The results of experiment II indicated that weight gain percentage, serum T3 and T4 levels were significantly reduced in groups that were exposed to temperature and salinity stress and fed diets without TRP supplementation. However, dietary supplementation of TRP significantly augmented weight gain percentage in stress-exposed groups. Tryptophan supplementation helped in bringing back T3 and T4 levels comparable with control. A significant increase in superoxide dismutase, catalase, Adenosine triphosphatase, blood glucose and serum cortisol was observed in temperature- and salinity-exposed groups fed without TRP-supplemented diets. However, TRP supplementation was found to be effective in restoring the above parameters. The results of these experiments suggest that dietary TRP supplementation augments growth, lowers energy demand and helps in mitigating thermal and salinity stress in L.rohita.

Effect of high-fat intake on motor activity, homovanillic acid and 5-hydroxyindoleacetic acid levels in striatum and cortex of rats exposed to stress

The aim of the present study was to investigate whether high fat consumption changes the effects of stress on both motor activity performance, striatal and cortical dopamine and serotonin metabolites in rats. The animals were fed either with high fat or standard diet for 4 weeks. Restraint stress lasting for 15 min at +4°C was applied daily to stress-exposed groups. Motor activity performance was measured weekly by using motor activity monitoring systems. At the end of the study, homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) levels of the striatum and cerebral cortex were measured by HPLCEC. It was observed that restraint stress increased locomotor activity and high-fat diet prevented this effect. Stress and high-fat intake had an additive decreasing effect on striatal HVA levels. 5-HIAA levels, on the other hand, were lower in both high fat and high fat + stress groups compared to the stress group. These results suggest that high-fat intake differentially affected the stress response on striatal dopaminergic and serotonergic neurons in rat brain regions studied and this may be related to the effects observed in motor activity performance.

반복 스트레스에 의한 흰쥐 해마조직내 신경전구세포의 생성과 brain-derived neurotrophic factor (BDNF) mRNA 발현 변동에 미치는 고려홍삼 사포닌의 반복 투여 효과

본 연구 결과를 통하여 홍삼 성분인 고려홍삼 사포닌을 반복 투여시 흰쥐 해마 SGZ 부위의 신경전구세포 생성이 유의하게 증가되었으며, 이와 같은 경향은 반복 스트레스에 노출되어도 유지되었다. 또한 스트레스를 가하지 않은 흰쥐에서 고려홍삼 사포닌 반복 투여시 해마 CA3와 CA1 부위에서 BDNF mRNA의 발현이 증가되었으나, 반복 스트레스를 가한 흰쥐의 CA3와 CA1부위에서 BDNF mRNA의 감소를 차단하지는 못하였다. 따라서 고려홍삼 사포닌 반복 처치에 의한 해마 신경전구세포의 생성에 BDNF 보다는 다른 요인이 관여할 가능성이 클 것으로 추정된다. Korean red ginseng is known to have anti-stress and memory enhancing effects. Recent studies suggested that stress-induced inhibition of adult neurogenesis in hippocampus may contribute, in part, to decreased negative feedback inhibition of HPA axis. In order to elucidate the mechanism of Korean red ginseng in anti-stress and memory enhancing effects, we observed the effects of repeated treatment of Korean red ginseng total saponin (GTS, 50 mg/kg, i.p.) in response to repeated unpredictable stress for 10 days. Male Sprague-Dawley rats (230 - 260 g) received with either GTS (50 mg/kg, i.p.) or vehicle (1 ml/kg, i.p.) 1 h before stress for 10 days. Rats were injected with bromodeoxyuridine (BrdU, 50 mg/kg, i.p.) 16-18 he after last stress procedure, and were sacrificed 2 hr later by perfusion. Immunohistochemistry of BrdU was done to measure proliferation of neural progenitor cells in hippocampus, which was used as an index of neurogenesis. Repeated GTS treatment for 10 days increased neurogenesis in subgranular zone area of dentate gyrus (SGZ), but not hilus, compared with vehicle-treated rats. Repeated unpredictable stress did not affect the neurogenesis compared with controls, while repeated GTS treatment increased neurogenesis in SGZ in repeated unpredictable stress-exposed group. BDNF mRNA was also measured in subregions of hippocampus by in situ hybridization. BDNF mRNA expression in CA3 and CA1 pyramidal cell layer was increased by repeated GTS treatment but not in dentate granule cell layer. Repeated unpredictable stresses significantly decreased BDNF mRNA expression in all subregions of hippocampus, but repeated GTS treatment did not prevent stress-induced BDNF mRNA downregulation. Given that repeated GTS treatment increased proliferation of neural progenitor cells in repeated unpredictable stress-exposed rats in the presence of decreased BDNF mRNA expression in dentate granule cell layer, it raise the possibility that BDNF may not playa significant role in GTS-mediated increase of neurogenesis in adult rat hippocampus. Also, these results suggest that repeated GTS treatment increased neurogenesis of SGZ and BDNF mRNA expression, which may account for memory enhancing effect of Korean red ginseng. In addition, repeated GTS treatment appears not to have anti-stress effects in terms of neurotrophin, but GTS-mediated increase of neurogenesis in hippocampus may contribute to increase negative feedback inhibition of HPA axis.

Gender-specific effects of social housing on chronic stress-induced limbic FOS expression

Stress plays an important role in the development of affective disorders. Women show a higher prevalence for these disorders then men. The course of a depressive episode is thought to be positively influenced by social support. We have used a chronic mild stress model in which rats received footshocks daily for 3 weeks. Since rats are social animals we hypothesised that social housing, as a possible model for human social support, might reduce the adverse effects of chronic stress. Brain activity after chronic stress was measured in several limbic brain areas with the neuronal activation marker c-fos. High behavioural activity due to housing rats under reversed light–dark conditions could be responsible for the observed high within group variability in some limbic regions. FOS- (ir) in the paraventricular nucleus of the hypothalamus (PVN) was increased in all stress-exposed groups, except for the socially housed females who showed increased FOS-ir in control condition. Individually housed males and socially housed females showed increased FOS-ir in the dorsal raphe (DRN). Amygdala nuclei were differentially affected by stress, gender and housing conditions. Also the mesolimbic dopaminergic system showed gender specific responses to stress and housing conditions. These results indicate that social support can enhance stress coping in female rats, whereas in males rats, group housing appears to increase the adverse effects of chronic stress, although the neurobiological mechanism is not simply a reduction or enhancement of stress-induced brain activation.

Gender-specific effects of social housing in rats after chronic mild stress exposure

Stress plays an important role in the development of affective disorders. Women show a higher prevalence for these disorders then men. The course of a depression is thought to be positively influenced by social support. The authors have used a chronic mild stress model in which rats received footshocks daily for 3 weeks. Since rats are social animals we hypothesized that ‘social support’ might reduce the adverse effects of chronic stress. To test this hypothesis, male and female rats were housed individually or socially in unisex groups of four rats. An open field test was repeated four times during the 3 weeks of treatment. Neuronal activation in the paraventricular nucleus of the hypothalamus (PVN) and dorsal raphe nucleus (DRN) in response to stress was measured the last day with c- fos. Chronic stress exposure increased locomotor activity in the open field, especially during the first minute. This was most pronounced in the individually housed females. In females, social housing prevented the stress-induced increase of locomotor activity, while in males social housing had no effect. Fos immunoreactive (FOS-ir) in the PVN was increased in all stress-exposed groups, except for the socially housed females due to a higher FOS-ir in controls. Individually housed males and socially housed females showed increased FOS-ir in the DRN and the increase was almost significant in socially housed males. In conclusion: These results show that social housing can enhance coping with stress in female rats, whereas in male rats group housing did not have a positive influence on stress-sensitivity.

High prevalence of stress hyperglycaemia in children with febrile seizures and traumatic injuries

Although hyperglycaemia is relatively frequent in the course of severe illnesses and may be looked upon as the possible result of an uncoordinated insulin response to the increased glucose that the body may need during periods of stress, it is generally agreed that it does not constitute a prediabetic condition. Numerous studies have aimed to explain the pathophysiology of this occurrence but none has looked at which conditions are more prone to develop stress hyperglycaemia (SH). Therefore, the aim of this study was to evaluate the main clinical conditions that may be associated with SH in children. A total of 1199 children was studied: 833 children (439 M, 394 F, mean age 5.2 +/- 4.5 y) admitted for an acute illness or injury constituted the stress-exposed group, while 366 children (222 M, 144 F, mean age 6.2 +/- 4.6 y) admitted for elective minor surgery represented the stress-unexposed group and were considered as the control group. SH was defined as plasma glucose concentrations > or = 8.3 mmol l(-1) during an acute illness. Stress-exposed patients had significantly higher glycaemic levels than controls (5.6 +/- 1.4 vs 4.7 +/- 0.7 mmol l(-1); p < 0.0001). SH was found in 41 (4.9%) stress-exposed patients and in none of the controls. SH was significantly more prevalent in children affected by febrile seizures (12.9%) or traumatic injuries (11.7%; p < 0.008 and p < 0.02, respectively, vs other diagnoses). A significant correlation was found between glycaemia and systolic pressure (r = 0.1; p < 0.01), white cell count (r = 0.12; p < 0.0003) and body temperature (r = 0.16; p < 0.0001). SH was more frequent in patients with body temperature > 39 degrees C (14%) than in those with a temperature < or = 39 degrees C (4%; p < 0.0008). SH was more prevalent in clinical conditions of fever associated with seizures or pain (12.9% and 12.5%, respectively) than fever alone (4.4%). After a mean period of 3.5 +/- 0.6 y of follow-up none of the hyperglycaemic patients had developed diabetes mellitus. Traumatic injuries, febrile seizures or conditions in which an elevated body temperature may be found are frequently associated with SH in children. In the presence of these conditions specific studies directed towards unmasking a prediabetic state may be unnecessary.

Effects of Predator-Induced Stress and Age on Working Memory in Rats

The effects of age and predator-induced stress, by exposing rats to a cat, were examined during subsequent testing of spatial working memory. Male rats (3 months and 20 months of age) were trained on a spatial delayed-alternation task using an elevated T maze. After subgroups were given intermittent protected-exposure sessions over a 3-day period to cats or to a control condition, they were tested on the working memory task. The old rats took more trials to reach training criterion. Overall, both stress-exposed groups exhibited a decline in accuracy 24 hr later and recovered completely during the subsequent test sessions. Surprisingly, young stressed rats showed significantly greater decrements in accuracy than old stressed rats. However, exposure to the stressor resulted in decreases in response speed that were comparable for both age groups. These findings are discussed in terms of possible changes in glucocorticoids, plasma corticosterone, and endogenous opioids that are known to be affected by age and stress and have been shown to influence spatial working memory.