Circadian clock functioning is linked to acute stress reactivity in rats

At least two major physiological systems are involved in the adaptation of the organism to environmental challenges: the circadian system and the stress reaction. This study addressed the possibility that interindividual differences in stress sensitivity and in the functioning of the circadian system are related. At 2 months of age, corticosterone secretion in response to a 20-min restraint stress was assessed in 9 Sprague-Dawley rats for which running wheel activity was recorded as a rhythmic behavioral marker of the circadian clock. Two weeks later, the adaptive response of the circadian system to an abrupt shift in the light:dark (LD) cycle was assessed in those rats using a jet-lag paradigm. Finally, after resynchronization to the new LD cycle, rats were transferred to constant darkness to assess the free-running period of their circadian rhythm of running-wheel activity. Results indicate that stress-induced corticosterone secretion was (1) positively correlated with the number of days to resynchronize the circadian activity rhythm to the new LD cycle, and with the value of its free-running period, and (2) negatively correlated with the intensity of daily locomotor activity. Those data, emphasizing the interactions between the stress response of an organism and the functioning of its circadian system, could explain interindividual differences in humans' susceptibility to shift work or other circadian-related disorders.     

Circadian preference,nighttime sleep and daytime functioning in young adulthood

Sleep and Biological Rhythms - The aim of this study was to investigate whether evening circadian preference, as measured by the Horne and Östberg questionnaire, is associated with disrupted...     

Central histaminergic involvement during stress in rats.

Effects of some drugs modulating central histaminergic (HA) transmission were evaluated on restraint stress (RS)-induced gastric ulcerogenesis, plasma corticosterone and immune responses in rats. RS for (i) 6 hr or (ii) 24 hr at room temperature, and (iii) 3 hr at 4 degrees C (CRS) all induced gastric mucosal erosions and elevated plasma corticosterone levels, the effects with the latter two RS procedures being most consistent. Pretreatment of rats with neuronal HA depletor, alpha-FMH (100 mg/kg, ip) attenuated both ulcer severity and corticosterone response, during both 24 hr RS and CRS. Similar effects were also seen with the mast cell degranulator, C-48/80 (10 micrograms/kg, i.c.v.) treatment. Further, the H1-blocker, pheniramine (25 mg/kg, ip) but not the centrally acting H2-blocker, zolantidine (5 mg/kg, ip) produced clearcut attenuations in both stress markers, during the experimental stressors. In rats immunized in SRBC, 24 hr RS (and not CRS) significantly prevented the humoral immune responses to the antigen. alpha-FMH, C 48/80 and pheniramine but not zolantidine, reversed this response during 24 hr RS. The results indicate a central HA ergic involvement in the visceral, endocrinal and immune responses during RS and suggest the probable role of both neuronal as well as extraneuronal (mast cell) HA and activation of H1-receptors in the mediation of these effects.     

Eveningness, sleep patterns, daytime functioning, and quality of life in Israeli adolescents

The purpose of the study was to assess the relationships between eveningness, sleep patterns, measures of daytime functioning, i.e., sleepiness, sleep problem behaviors, and depressed mood, and quality of life (QOL) in young Israeli adolescents. A cross-sectional survey was performed in urban and rural middle schools in Northern Israel. Participants were 470 eighth and ninth grade middle school students (14?±?0.8 yrs of age) in the normative school system. Students completed the modified School Sleep Habits Survey (SSHS) and Pediatric Quality of Life Inventory Short Form, assessing six subscales of physical, emotional, social, school performance, and psychosocial functioning, plus an addition generated total score. During weekdays and weekends, evening types went to bed later, their sleep latency was longer, their wake-up time was later, and their sleep duration was shorter than intermediate and morning types. Evening types exhibited more sleep problem behaviors, sleepiness, depressed mood, and lower QOL compared to intermediate and morning types. Based on the regression model, sleepiness, sleep-problem behaviors, and depressed mood were the variables most strongly associated with QOL, followed by morning-evening preference, weekday sleep duration, and weekend sleep latency. This study is the first to assess QOL in normative, healthy adolescents and to demonstrate strong associations between morning-evening preference and QOL. These findings enhance the need to identify young individuals with an evening preference, and to be aware of the characteristics and manifestations of the evening chronotype on daytime and nighttime behaviors in adolescence.     

Adaptational effect of dimethylsulfoxide during chronic emotional-painful stress in rats

Intraperitoneal injection of hydroxyl radical scavenger dimethyl sulfoxide (DMSO) to rats (1 g/kg body weight, daily for 3 weeks) did not change their behaviour in the open field and had no effect on blood pressure and heart and respiratory rates. DMSO injection before stress prevented changes usually induced by chronic (three-week) emotional-painful stress. DMSO increased superoxide dismutase activity in brain homogenates and serum. It is suggested that hydroxyl radicals (OH) play the key role in the realization of stress-induced effects and that molecular mechanisms of anti-stress effects of DMSO include both scavenging of hydroxyl radicals and activation of superoxide dismutase.     

Investigation of oxidative stress during fracture healing in the rats

One of the most damaging effects of reactive oxygen species (ROS) is lipid peroxidation, the end-product of which is malondialdehyde (MDA). This study was aimed to evaluate erythrocyte MDA levels during fracture healing in rats. Thirty male rats were used and the rats were divided into two groups to serve as controls and tests. Six rats were used as a control group that was not subject to fracture. The remaining 24 rats were divided into four groups and erythrocyte MDA levels were examined on days 5, 10, 20 and 30 post fracture. The right fibulas of rats were broken by manual angulation in the experimental group. The erythrocyte malondialdehyde level was measured in the experimental and control groups. The difference between malondialdehyde levels of control and experimental groups was statistically significant (p<0.05). Oxidative stress clearly increases during fracture healing in rats.     

Sex differences in response to stress in conscious and anesthesized rats during surgical stress]

Adrenal and plasma corticosterone levels under conditions of preoperative stress (removal from animal to experimental rooms, removal from a home cage, handling, weighing and injecting with saline) were more than 2-fold higher in female rats than in male ones. Females, compared with males, showed more pronounced decrease in corticosterone responses to preoperative stress and laparotomy under nembutal anesthesia, which blocked stress-induced emotional activation. One hour after recovery from anesthesia laparotomized females but not males, demonstrated a significant (5-fold) increase in plasma corticosterone level. The absolute values of plasma corticosterone in laparotomized females, compared with males, were 2-fold lower under anesthesia but 2-fold higher after recovery from anesthesia. It is supposed that in females, compared with males, stress-induced emotional tension plays more considerable role in endocrine stress responses. This provides higher adrenocortical sensitivity to stress in conscious female rats than in male animals.     

Electroreceptor functioning and morphology: functioning during histological fixation

The impact of chemical fixatives on electroreceptor functioning was studied electrophysiologically. The oxidative agents KMnO4 and OsO4 eliminate the sensory response within a few seconds, leaving a disturbed spike train pattern. Glutaraldehyde and formaldehyde eliminate the sensory response gradually in a period of several minutes; after that the afferent fibre shows repetitive activity. It is concluded that the physiological state of the electroreceptor is not preserved during chemical fixation; the ultimate morphological picture will reflect an unphysiological state, i.e. the response to the fixative.     

Nigrostriatal dopaminergic activity is increased during exhaustive exercise stress in rats

Exercise capacity is influenced by both increases and decreases in central dopaminergic activity. To investigate the effects of exercise stress on intracerebral dopamine metabolism, rats were run on a motor driven treadmill at 37 m/min for varying times up to exhaustion at 19.6 +/- 0.6 min. Dopamine, DOPAC, and HVA concentrations in striatum, brain stem, and hypothalamus increased towards exhaustion. 5-HIAA concentrations increased in striatum whereas norepinephrine concentrations decreased in hypothalamus. The results indicate that delayed increases in dopaminergic activity occurs during exercise. These, and other observations indicate that central dopaminergic activity modulates exercise performance.     

Lipid peroxidation in the rats striatum during stress after cortisol administration

Lipid peroxidation in the rat striatum under stress after cortisole injection was investigated. Three days cortisole injections (25 mg/kg every day) do not affect the level of lipid peroxidation products 6 days after termination of the hormone injection. However, in these periods, cortisole injected rats had a more significant response of lipid peroxidation to stress than the control animals (decrease of intermediate products and increase of Shift bases). Thus, the hormone injection induced a long-term changes in so important a regulatory system of the organisms as the lipid peroxidation, causing sensitization of its response to stress.     

Dantrolene protects erythrocytes against oxidative stress during whole-body irradiation in rats

In our study, we examined the radioprotective effects of dantrolene against gamma irradiation-induced damage of blood cells after total body irradiation of rats. Rats were divided into three groups of eight rats each. The first group was the control group receiving no dantrolene or irradiation, the second group received total body irradiation (RT) with 5 Gy of gamma irradiation only, and the third group received dantrolene at a dose of 5 mg x kg(-1) plus RT. Dantrolene was given intraperitoneally 30 min before RT. All groups were sacrificed 2 h after RT, and blood samples were taken. Leukocyte, and thrombocyte counts and hemoglobin levels were measured. Furthermore, malondialdehyde (MDA) levels in plasma and erythrocytes and superoxide dismutase (SOD) and glutathione peroxidase activities (GSH-Px) in erythrocytes were determined. It was found that pretreatment with dantrolene at a dose of 5 mg x kg(-1) significantly reduced the MDA levels and increased the antioxidant SOD and GSH-Px activities, and prevented the decrease in leukocyte and thrombocyte counts. We conclude that dantrolene has clear antioxidant properties when given prior to radiation exposure and the protective effect of dantrolene against damage inflicted by radiation, depends, at least in part, on the decrease in lipid peroxidation and increase in the activity of antioxidant enzymes SOD and GSH-Px.     

Athletes underestimate sleep quantity during daytime nap opportunities

ABSTRACT

This study examined the difference between athletes’ self-reported and objective sleep durations during two nap opportunities. Twelve well-trained male soccer players’ sleep durations were assessed using polysomnography and a self-report question during a 60- and 120-min nap opportunity. Participants underestimated sleep compared to objective sleep assessments for both the 60-min nap opportunity (p = 0.004) and 120-min nap opportunity (p = 0.001). Soccer players underestimated their sleep duration by approximately 10 min per hour of nap opportunity. It is yet to be determined if athletes are likely to underestimate sleep duration during their main nighttime sleep period.     

Curcumin ameliorates oxidative stress during nicotine-induced lung toxicity in Wistar rats

Nicotine, a major toxic component of cigarette smoke has been identified as a major risk factor for lung related diseases. In the present study, we evaluated the protective effects of curcumin on lipid peroxidation and antioxidants status in bronchoalveolar lavage fluid (BALF) and bronchoalveolar lavage (BAL) of nicotine treated Wistar rats. Lung toxicity was induced by subcutaneous injection of nicotine at a dose of 2.5 mg/kg body weight (5 days a week, for 22 weeks) and curcumin (80 mg/kg body weight) was given simultaneously by intragastric intubation for 22 weeks. Measurement of biochemical marker enzymes: alkaline phosphatase, lactate dehydrogenase, lipid peroxidation and antioxidants were used to monitor the antiperoxidative effects of curcumin. The increased biochemical marker enzymes as well as lipid peroxides in BALF and BAL of nicotine treated rats was accompanied by a significant decrease in the levels of glutathione, glutathione peroxidase, superoxide dismutase and catalase. Administration of curcumin significantly lowered the biochemical marker enzymes, lipid peroxidation and enhanced the antioxidant status. The results of the present study suggest that curcumin exert its protective effect against nicotine-induced lung toxicity by modulating the biochemical marker enzymes, lipid peroxidation and augmenting antioxidant defense system.     

Bright light during lactation alters the functioning of the circadian system of adult rats

To examine the role of light in the maturation of the circadian pacemaker, twelve groups of rats were raised in different conditions of exposure to constant bright light (LL) during lactation: both duration and timing of LL were varied. We studied the motor activity rhythm of the rats after weaning, first under LL and then under constant darkness (DD). In DD, two light pulses [at circadian time 15 (CT15) and CT22] were applied to test the response of the pacemaker. Greater exposure to LL days during lactation increased the number of rhythmic animals and the amplitude of their motor activity rhythm in the LL stage and decreased the phase delay due to the light pulse at CT15. The timing of LL during lactation affected these variables too. Because the response of the adult to light depended on both the number and timing of LL days during lactation, the exposure to light at early stages may influence the development of the circadian system by modifying it structurally or functionally.     

Effect of ionol on the stomach lesion in rats during immobilization stress

Intragastric administration of the antioxidant ionol (50 mg/kg/a day) for 7 days did not prevent the formation of ulcers or massive hemorrhages to the gastric mucosa in immobilized animals, increased the number of petechiae and lowered that of erosions. In this case the parietal pH increased in the stomach and dropped in the remaining divisions of the alimentary tract. The combined action of stress and ionol brought about marked hypocoagulation. Ionol exerted a protective action on the stress-induced activation of lipid peroxidation in the stomach but did not produce any such effect on the liver.