Body weight gain, food intake and adrenal development in chronic noise stressed rats

Ferulic Acid-Loaded Nanostructure Maintains Brain Levels of ACh, Glutamate, and GABA and Ameliorates Anxiety and Memory Impairments Induced by the D-Galactose Aging Process in Rats

Population aging is a global reality driven by increased life expectancy. This demographic phenomenon is intrinsically linked to the epidemic of cognitive disorders such as dementia and Alzheimer's disease, posing challenges for elderly and their families. In this context, the search for new therapeutic strategies to prevent or minimize cognitive impairments becomes urgent, as these deficits are primarily associated with oxidative damage and increased neuroinflammation. Ferulic acid (FA), a natural and potent antioxidant compound, is proposed to be nanoencapsulated to target the central nervous system effectively with lower doses and an extended duration of action. Here, we evaluated the effects of the nanoencapsulated FA on d-galactose (d-Gal)- induced memory impairments. Male Wistar adult rats were treated with ferulic acid-loaded nanocapsules (FA-Nc) or non-encapsulated ferulic acid (D-FA) for 8 weeks concurrently with d-Gal (150 mg/kg s.c.) injection. As expected, our findings showed that d-Gal injection impaired memory processes and increased anxiety behavior, whereas FA-Nc treatment ameliorated these behavioral impairments associated with the aging process induced by d-Gal. At the molecular level, nanoencapsulated ferulic acid (FA-Nc) ameliorated the decrease in ACh and glutamate induced by d-galactose (d-Gal), and also increased GABA levels in the dorsal hippocampus, indicating its therapeutic superiority. Additional studies are needed to elucidate the mechanisms underlying our current promising outcomes. Nanoscience applied to pharmacology can reduce drug dosage, thereby minimizing adverse effects while enhancing therapeutic response, particularly in neurodegenerative diseases associated with aging. Therefore, the strategy of brain-targeted drug delivery through nanoencapsulation can be effective in mitigating aging-related factors that may lead to cognitive deficits.

PPARα suppresses low-intensity-noise-induced body weight gain in mice: the activated HPA axis plays an critical role

BACKGROUND

As the second most risky environmental pollution, noise imposes threats to human health. Exposure to high-intensity noise causes hearing impairment, psychotic disorders, endocrine modifications. The relationship among low-intensity noise, obesity and lipid-regulating nuclear factor PPARα is not yet clear.

METHODS

In this study, male wild-type (WT) and Pparα-null (KO) mice on a high-fat diet (HFD) were exposed to 75 dB noise for 12 weeks to explore the effect of low-intensity noise on obesity development and the role of PPARα. 3T3-L1 cells were treated with dexamethasone (DEX) and sodium oleate (OA) to verify the down-stream effect of hypothalamic-pituitary-adrenal (HPA) axis activation on the adipose tissues.

RESULTS

The average body weight gain (BWG) of WT mice on HFD exposed to noise was inhibited, which was not observed in KO mice. The mass and adipocyte size of adipose tissues accounted for the above difference of BWG tendency. In WT mice on HFD, the adrenocorticotropic hormone level was increased by the noise challenge. The aggravation of fatty liver by noise exposure occurred in both mouse lines, and the transport of hepatic redundant lipid to adipose tissues were similar. The lipid metabolism in adipose tissue driven by HPA axis accorded with the BWG inhibition in vivo, validated in 3T3-L1 adipogenic stem cells.

CONCLUSION

Chronic exposure to low-intensity noise aggravated fatty liver in both WT and KO mice. BWG inhibition was observed only in WT mice, which covered up the aggravation of fatty liver by noise exposure. PPARα mediates the activation of HPA axis by noise exposure in mice on HFD. Elevated adrenocorticotropic hormone (ACTH) promoted lipid metabolism in adipocytes, which contributed to the disassociation of BWG and fatty liver development in male WT mice. Summary of PPARα suppresses noise-induced body weight gain in mice on high-fat-diet. Chronic exposure to low-intensity noise exposure inhibited BWG by PPARα-dependent activation of the HPA axis.

Dysregulation of circadian clock gene expression patterns in a treatment-resistant animal model of depression

Circadian rhythm (CR) disturbances are among the most commonly observed symptoms during major depressive disorder, mostly in the form of disrupted sleeping patterns. However, several other measurable parameters, such as plasma hormone rhythms and differential expression of circadian clock genes (ccgs), are also present, often referred to as circadian phase markers. In the recent years, CR disturbances have been recognized as an essential aspect of depression; however, most of the known animal models of depression have yet to be evaluated for their eligibility to model CR disturbances. In this study, we investigate the potential of adrenocorticotropic hormone (ACTH)-treated animals as a disease model for research in CR disturbances in treatment-resistant depression. For this purpose, we evaluate the changes in several circadian phase markers, including plasma concentrations of corticosterone, ACTH, and melatonin, as well as gene expression patterns of 13 selected ccgs at 3 different time points, in both peripheral and central tissues. We observed no impact on plasma corticosterone and melatonin concentrations in the ACTH rats compared to vehicle. However, the expression pattern of several ccgs was affected in the ACTH rats compared to vehicle. In the hippocampus, 10 ccgs were affected by ACTH treatment, whereas in the adrenal glands, 5 ccgs were affected and in the prefrontal cortex, hypothalamus and liver 4 ccgs were regulated. In the blood, only 1 gene was affected. Individual tissues showed changes in different ccgs, but the expression of Bmal1, Per1, and Per2 were most generally affected. Collectively, the results presented here indicate that the ACTH animal model displays dysregulation of a number of phase markers suggesting the model may be appropriate for future studies into CR disturbances.

Effect of chronic noise exposure on glucose and lipid metabolism in mice via modulating gut microbiota and regulating CREB/CRTC2 and SREBP1/SCD pathway

Chronic noise exposure is correlated with gut microbiota dysbiosis and glucose and lipid metabolism disorders. However, evidence on the mechanisms underlying of gut microbiota alterations in chronic noise induced glucose and lipid metabolism disorders is limited, and the potential aftereffects of chronic noise exposure on metabolic disorders remain unclear. In present study, we established chronic daytime and nighttime noise exposure mice models to explore the effects and underlying mechanism of gut microbiota on chronic noise-induced glucose and lipid metabolism disorders. The results showed that exposure to chronic daytime or nighttime noise significantly increased the fasting blood glucose, serum and liver TG levels, impaired glucose tolerance, and decreased serum HDL-C levels and liver TC levels in mice. However, after 4 weeks of recovery, only serum TG of mice in nighttime noise recovery group remained elevated. Besides, exposure to chronic noise reduced the intestinal tight junction protein levels and increased intestinal permeability, while this effect did not completely dissipate even after the recovery period. Moreover, chronic noise exposure changed the gut microbiota and significantly regulated metabolites and metabolic pathways, and further activate hepatic gluconeogenesis CRTC2/CREB-PCK1 signaling pathway and lipid synthesis SREBP1/SCD signaling pathway through intestinal hepatic axis. Together, our findings demonstrated that chronic daytime and nighttime noise exposure could cause the glucose and lipid metabolism disorder by modulating the gut microbiota and serum metabolites, and activating hepatic gluconeogenic CREB/CRTC2-PCK1 signaling and lipid synthesis SREBP1/SCD signaling pathway. The potential aftereffects of noise exposure during wakefulness on metabolic disorders are more significant than that of noise exposure during sleep.

Acute Wheel-Running Increases Markers of Stress and Aversion-Related Signaling in the Basolateral Amygdala of Male Rats

Physical activity (PA) is a non-invasive, cost-effective means of reducing chronic disease. Most US citizens fail to meet PA guidelines, and individuals experiencing chronic stress are less likely to be physically active. To better understand the barriers to maintaining active lifestyles, we sought to determine the extent to which short- versus long-term PA increases stress- and aversion-related markers in wild-type (WT) and low voluntary running (LVR) rats, a unique genetic model of low physical activity motivation. Here, we tested the effects of 1 and 4 weeks of voluntary wheel-running on physiological, behavioral, and molecular measures of stress and Hypothalamic Pituitary Adrenal (HPA)-axis responsiveness (corticosterone levels, adrenal wet weights, and fecal boli counts). We further determined measures of aversion-related signaling (kappa opioid receptor, dynorphin, and corticotropin releasing hormone mRNA expression) in the basolateral amygdala (BLA), a brain region well characterized for its role in anxiety and aversion. Compared to sedentary values, 1, but not 4 weeks of voluntary wheel-running increased adrenal wet weights and plasma corticosterone levels, suggesting that HPA responsiveness normalizes following long-term PA. BLA mRNA expression of prodynorphin (Pdyn) was significantly elevated in WT and LVR rats following 1 week of wheel-running compared to sedentary levels, suggesting that aversion-related signaling is elevated following short- but not long-term wheel-running. In all, it appears that the stress effects of acute PA may increase molecular markers associated with aversion in the BLA, and that LVR rats may be more sensitive to these effects, providing a potential neural mechanism for their low PA motivation.

Combined effects of the exposure to silver nanoparticles and noise on hearing function and cochlea structure of the male rats

AIMS

This study intended to investigate whether exposure to the combination of noise and Ag-NPs in rats induces cochlear damage and hearing dysfunction.

MAIN METHODS

A total of 24Wistar rats were divided into four treatment groups and received/exposed to saline (IP), Ag-NPs (100 mg/kg, 5d/w for 4 weeks), 8 kHz narrowband noise (104 dB SPL, 6 h/day, 5d/w for 4 weeks) and Ag-NPs plus noise. The DPOAE, serum levels of MDA and SOD and changes in body weight were assessed. The rat cochlea was further stained for investigating the mRNA expression (TL-6, NOX3, and TNF-), IHC (TUJ-1 and MHC7), and histological alterations. The Ag-NPs characteristics were also analysed by SEM and XRD.

KEY FINDINGS

DPOAE values were remarkably reduced (p < 0.05) among the exposed groups. Furthermore, exposure to noise and Ag-NPs significantly increased MDA levels and decreased the SOD activity in the serum. In comparison to the control group, the expression of IL-6, TNF-, and NOX3 was shown to be elevated in the Ag-NPs plus noise group. The body weight also increased significantly in all groups with the exception of the Ag-NPs plus noise group. IHC tests showed remarkable down-regulation of TUJ1 and MYO7A. Morphological changes confirmed our findings as well. SEM and XRD data validated the production of Ag-NPs.

SIGNIFICANCE

According to the findings of this study, sub-acute exposure to noise and Ag-NPs causes permanent damage to the hair cells that are in charge of high-frequency perception.

Neuroendocrine control of appetite and metabolism

Body homeostasis is predominantly controlled by hormones secreted by endocrine organs. The central nervous system contains several important endocrine structures, including the hypothalamic-pituitary axis. Conventionally, neurohormones released by the hypothalamus and the pituitary gland (hypophysis) have received much attention owing to the unique functions of the end hormones released by their target peripheral organs (e.g., glucocorticoids released by the adrenal glands). Recent advances in mouse genetics have revealed several important metabolic functions of hypothalamic neurohormone-expressing cells, many of which are not readily explained by the action of the corresponding classical downstream hormones. Notably, the newly identified functions are better explained by the action of conventional neurotransmitters (e.g., glutamate and GABA) that constitute a neuronal circuit. In this review, we discuss the regulation of appetite and metabolism by hypothalamic neurohormone-expressing cells, with a focus on the distinct contributions of neurohormones and neurotransmitters released by these neurons.

Effect of chronic corticosterone treatment on expression and distribution of serotonin 5-HT7 receptors in rat adrenal glands

Sensitized stress-induced corticosterone (CORT) secretion in chronically stressed rats involves 5-HT7 receptor activation. The effect of 14-day chronic CORT and vehicle (VEH) administration on 5-HT7 receptor expression in adrenal glands, adrenal 5-HT content, and adrenocorticotropic hormone and CORT secretion was analysed. On day 15, VEH- and CORT-treated animals were perfused or decapitated without stress exposure (0 min) or after 10 and 30 min of restraint for collection of trunk blood and tissues. 5-HT7 receptor-like immunoreactivity (5-HT7R-LI), 5-HT7 receptor protein, and mRNA levels were determined by immunohistochemistry, Western blot, and reverse transcription polymerase chain reaction assays, respectively; 5-HT levels and hormones were quantified using HPLC and ELISA kits, respectively. An undisturbed control group was included for most experimental comparisons. Chronic CORT strongly increased 5-HT7R-LI in the outer adrenal cortex, as well as 5-HT7 receptor protein and mRNA in whole adrenal glands; adrenal 5-HT content also increased in these animals. Decreased adrenocorticotropic hormone and CORT secretion at 30 min of restraint occurred in CORT-treated rats. The results support the notion that chronic stress-induced increase of adrenocortical 5-HT7 receptors and adrenal 5-HT content is a glucocorticoid-dependent phenomenon; the development of magnified stress-induced 5-HT7 receptor-mediated CORT responses in chronically stressed animals nevertheless likely involves additional mechanisms.

Biological, Behavioral and Physiological Consequences of Drug-Induced Pregnancy Termination at First-Trimester Human Equivalent in an Animal Model

Given the significant physiological changes that take place during and resulting from pregnancy, as well as the relative absence of such information in relation to pregnancy termination, this study investigated the potential for developing a valid animal model to objectively assess the biological, physiological and behavioral consequences of drug-induced pregnancy termination. Female Long-Evans rats were divided into four groups (n = 19-21/group), controlling for drug [mifepristone (50 mg/kg/3 ml, i.g.)/misoprostol (0.3 mg/kg/ml, i.g.) or vehicle (1% Carboxymethylcellulose Sodium/0.2% Tween® 80 suspension, i.g.)] and pregnancy. Drug administration took place on days 12-14 of gestation (days 28-40 human gestational equivalent). Vehicle was administered to the controls on the same days. Parameters measured included rat body weight, food intake, vaginal impedance, sucrose consumption/preference, locomotor activity, forced swim test, and home-cage activity. At the termination of the study, rats were deeply anesthetized using urethane, and blood, brain, and liver were collected for biochemical analysis. Following drug/vehicle administration, only the pregnancy termination group (pregnant, drug) displayed a significant decrease in body weight, food intake, locomotor activity-related behaviors and home-cage activity relative to the control group (non-pregnant, vehicle). Additionally, the pregnancy termination group was the only group that displayed a significant reduction in sucrose consumption/preference during Treatment Week relative to Pre-Treatment Week. Vaginal impedance did not significantly decrease over time in parous rats in contrast to all other groups, including the rats in the pregnancy termination group. Biochemical analysis indicated putative drug- and pregnancy-specific influences on oxidative balance. Regression analysis indicated that pregnancy termination was a predictor variable for body weight, food intake and all locomotor activity parameters measured. Moreover, pertaining to body weight and food intake, the pregnancy termination group displayed significant changes, which were not present in a group of naturally miscarrying rats following pregnancy loss. Overall, our results appear to suggest negative biological and behavioral effects following pregnancy termination, that appear to also be distinct from natural miscarriage, and potential benefits of parity pertaining to fecundity. Thus, our findings indicate the importance for further objective investigation of the physiological and behavioral consequences of medical abortion, in order to provide further insight into the potential implications in humans.

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model

BACKGROUND

Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate.

OBJECTIVE

The objective of the present study was to assess the effects of subchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats.

METHODS

Twenty-four 3-wk-old male Wistar rats were exposed to noise [[Formula: see text], [Formula: see text]] for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded.

RESULTS

Five weeks of high-level noise exposure were associated with hyperphagia ([Formula: see text]), body weight gain ([Formula: see text]), a heavier thymus ([Formula: see text]), and heavier adrenal glands ([Formula: see text]). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min).

DISCUSSION

Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure. https://doi.org/10.1289/EHP4045.

Chronic dexamethasone exposure retards growth without altering the digestive tract microbiota composition in goats

Background

Dexamethasone (Dex), an artificially synthetic cortisol substitute, is commonly used as an anti-inflammatory drug, and is also employed to mimic the stress state experimentally. It is well known that chronic stress disturbs the gut microbiota community and digestive functions. However, no relevant studies have been conducted in ruminants.

Results

In this study, a low dosage of Dex (0.2 mg/kg body weight, Dex group, n = 5) was consecutively injected intramuscularly for 21 days to simulate chronic stress in growing goats. Goats were injected with saline (0.2 mg/kg body weight) as the control group (Con, n = 5). Dex-treated goats showed a higher number of white blood cells and blood glucose levels (p < 0.01), but lower dry matter intake (DMI) and body weight (p < 0.01) than those of saline-injected goats. Plasma cortisol concentration decreased significantly in response to the Dex injection compared to the control (p < 0.05). The Dex treatment did not change most ruminal volatile fatty acid (VFAs) concentrations before the morning feeding after 1–21 days of treatment (p > 0.05); however, ruminal VFA concentrations decreased dramatically 2, 4, 6, and 8 h after the morning feeding on day 21 of the Dex injections. In this study, chronic Dex exposure did not alter the community structure of microbes or methanogenes in the rumen, caecum, or colonic digesta. Only Prevotella increased on days 7 and 14 of Dex treatment, but decreased on day 21, and Methanosphaera was the only genus of methanogene that decreased.

Conclusions

Our results suggest that chronic Dex exposure retards growth by decreasing DMI, which may be mediated by higher levels of blood glucose and lower ruminal VFA production. Microbiota in the digestive tract was highly resistant to chronic Dex exposure.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1253-1) contains supplementary material, which is available to authorized users.

Effects of Noise Exposure on Systemic and Tissue-Level Markers of Glucose Homeostasis and Insulin Resistance in Male Mice

BACKGROUND

Epidemiological studies have indicated that noise exposure is associated with an increased risk of type 2 diabetes mellitus (T2DM). However, the nature of the connection between noise exposure and T2DM remains to be explored.

OBJECTIVES

We explored whether and how noise exposure affects glucose homeostasis in mice as the initial step toward T2DM development.

METHODS

Male ICR mice were randomly assigned to one of four groups: the control group and three noise groups (N20D, N10D, and N1D), in which the animals were exposed to white noise at 95 decibel sound pressure level (dB SPL) for 4 hr per day for 20 successive days, 10 successive days, or 1 day, respectively. Glucose tolerance and insulin sensitivity were evaluated 1 day, 1 week, and 1 month after the final noise exposure (1DPN, 1WPN, and 1MPN). Standard immunoblots, immunohistochemical methods, and enzyme-linked immunosorbent assays (ELISA) were performed to assess insulin signaling in skeletal muscle, the morphology of β cells, and plasma corticosterone levels.

RESULTS

Noise exposure for 1 day caused transient glucose intolerance and insulin resistance, whereas noise exposure for 10 and 20 days had no effect on glucose tolerance but did cause prolonged insulin resistance and an increased insulin response to glucose challenge. Akt phosphorylation and GLUT4 translocation in response to exogenous insulin were decreased in the skeletal muscle of noise-exposed animals.

CONCLUSIONS

Noise exposure at 95 dB SPL caused insulin resistance in male ICR mice, which was prolonged with longer noise exposure and was likely related to the observed blunted insulin signaling in skeletal muscle.

CITATION

Liu L, Wang F, Lu H, Cao S, Du Z, Wang Y, Feng X, Gao Y, Zha M, Guo M, Sun Z, Wang J. 2016. Effects of noise exposure on systemic and tissue-level markers of glucose homeostasis and insulin resistance in male mice. Environ Health Perspect 124:1390-1398; http://dx.doi.org/10.1289/EHP162.

Coping with a changing soundscape: avoidance, adjustments and adaptations

Since the industrial age, background anthropogenic noise has become a pervasive feature of many habitable environments. This relatively recent environmental feature can be particularly challenging for organisms that use acoustic forms of communication due to its propensity for masking and decreasing the potential acoustic space of signals. Furthermore, anthropogenic noise may affect biological processes including animal interactions, physiological and behavioural responses to stimuli and cognitive development. However, animals' cognitive abilities may enable them to cope with high levels of anthropogenic noise through learning, the employment of acoustic and behavioural flexibility as well as the use of multi-modal sensory systems. We are only just beginning to understand how neural structures, endocrine systems and behaviour are mechanistically linked in these scenarios, providing us with information we can use to mitigate deleterious effects of pervasive noise on wildlife, along with highlighting the remarkable adaptability of animals to an increasingly anthropogenic world. In this review, I will focus mainly on birds, due to the amount of literature on the topic, and survey recent advancements made in two main spheres: (1) how anthropogenic noise affects cognitive processes and (2) how cognition enables animals to cope with increasingly noisy environments. I will be highlighting current gaps in our knowledge, such as how noise might impact behavioural traits such as predation, as well as how noise causes physical damage to neurotransmitters and affects stress levels, in order to direct future studies on this topic.

Predation risk modulates diet-induced obesity in male C57BL/6 mice

OBJECTIVE

In this study, the behavioral and physiological changes induced by experimentally varying the risk of predation in male mice fed a high-fat diet were examined. In particular, the study aimed to assess whether the risk of being predated modulates the body weight gain, providing an ecological context for the obesity resistance observed in many species of small mammals.

METHODS

Body weight, food intake, physical activity, and core body temperature of 35 male C57BL/6 mice were monitored for 20 days, while feeding a high-fat diet. A third of the animals were exposed to elevated risk of predation through exposure to the sounds of nocturnal predatory birds, and these were compared to animals exposed to a neutral noise or silence.

RESULTS

Male mice exposed to predation risk had significantly lower weight gain than the neutral or silent groups. Reduced food intake and increased physical activity were the main proximal factors explaining this effect. The risk of predation also induced changes in boldness.

CONCLUSIONS

This study provides evidence supporting the role of predation risk on body weight gain of small mammals.

Social exclusion intensifies anxiety-like behavior in adolescent rats

Social connection reduces the physiological reactivity to stressors, while social exclusion causes emotional distress. Stressful experiences in rats result in the facilitation of aversive memory and induction of anxiety. To determine the effect of social interaction, such as social connection, social exclusion and equality or inequality, on emotional change in adolescent distressed rats, the emotional alteration induced by restraint stress in individual rats following exposure to various social interaction circumstances was examined. Rats were assigned to one of the following groups: all freely moving rats, all rats restrained, rats restrained in the presence of freely moving rats and freely moving rats with a restrained rat. No significant difference in fear-memory and sucrose consumption between all groups was found. Change in body weight significantly increased in freely moving rats with a restrained rat, suggesting that those rats seems to share the stressful experience of the restrained rat. Interestingly, examination of the anxiety-like behavior revealed only rats restrained in the presence of freely moving rats to have a significant increase, suggesting that emotional distress intensifies in positions of social exclusion. These results demonstrate that unequally excluded social interaction circumstances could cause the amplification of distressed status and anxiety-related emotional alteration.

Androgen receptor-mediated regulation of adrenocortical activity in the sand rat, Psammomys obesus

The wild sand rat, Psammomys obesus, displays seasonal variations in adrenocortical activity that parallel those of testicular activity, indicating functional cross-talk between the hypothalamo-pituitary-adrenal and hypothalamo-pituitary-gonadal axes. In the present study, we examined androgen receptor (AR)-mediated actions of testicular steroids in the regulation of adrenocortical function in the sand rat. Specifically, we examined the expression of AR in the adrenal cortex, as well as adrenal apoptosis in male sand rats that had been surgically castrated or castrated and supplemented with testosterone; biochemical indices of adrenocortical function and hormone profiles were also measured. Orchiectomy was followed by an increase in adrenocorticotropic hormone secretion from the anterior pituitary and subsequently, increased adrenocortical activity; the latter was evidenced by orchiectomy-induced increases in the adrenal content of cholesterol and lipids as well as adrenal hypertrophy (seen as an elevation of the RNA/DNA ratio). Further, androgen deprivation respectively up- and downregulated the incidence of apoptosis within the glucocorticoid-producing zona fasciculata and sex steroid-producing zona reticularis. Interestingly, orchiectomy resulted in increased expression of AR in the zona fasciculata. All of the orchiectomy-induced cellular and biochemical responses were reversible after testosterone substitution therapy. Together, these data suggest that adrenocortical activity in the sand rat is seasonally modulated by testicular androgens that act through AR located in the adrenal cortex itself.

Experimental chronic noise is related to elevated fecal corticosteroid metabolites in lekking male greater Sage-Grouse (Centrocercus urophasianus)

There is increasing evidence that individuals in many species avoid areas exposed to chronic anthropogenic noise, but the impact of noise on those who remain in these habitats is unclear. One potential impact is chronic physiological stress, which can affect disease resistance, survival and reproductive success. Previous studies have found evidence of elevated stress-related hormones (glucocorticoids) in wildlife exposed to human activities, but the impacts of noise alone are difficult to separate from confounding factors. Here we used an experimental playback study to isolate the impacts of noise from industrial activity (natural gas drilling and road noise) on glucocorticoid levels in greater sage-grouse (Centrocercus urophasianus), a species of conservation concern. We non-invasively measured immunoreactive corticosterone metabolites from fecal samples (FCMs) of males on both noise-treated and control leks (display grounds) in two breeding seasons. We found strong support for an impact of noise playback on stress levels, with 16.7% higher mean FCM levels in samples from noise leks compared with samples from paired control leks. Taken together with results from a previous study finding declines in male lek attendance in response to noise playbacks, these results suggest that chronic noise pollution can cause greater sage-grouse to avoid otherwise suitable habitat, and can cause elevated stress levels in the birds who remain in noisy areas.

MDMA (ecstasy) enhances loud noise-induced morphofunctional alterations in heart and adrenal gland

Noise is an environmental stressor increasingly more present in modern life and, in particular, in a variety of recreational contexts. The aim of this work is to show the effects of noise on the myocardium and adrenal gland, through a careful review of the literature dealing with the peripheral effects of noise exposure in experimental and clinical studies. Noise induces adverse effects in human health, principally involving the cardiovascular and autonomic nervous systems, and the endocrine apparatus. Several factors in recreational environments potentially worsen the effects induced by loud noise. Among these, the intake of 3,4-methylenedioxymethamphetamine (MDMA) is frequently associated with noise exposure in recreational situations, because of its high compliance within social and relaxation settings. For this reason, MDMA is defined as a club drug--as its intake by young people often occurs in association with other factors, such as aggregation, high temperatures, and noise. It is known that self-administration of MDMA by humans causes severe toxicity. In particular, the myocardium is affected early after MDMA intake--resulting in tachycardia, hypertension, and arrhythmia. Furthermore, MDMA alters the activity of the adrenal glands by elevating catecholamines and corticosterone levels. This review shows that combining MDMA and loud noise exposure potentiates the effects that are produced by each single stimulant alone as seen in experimental animal models. The convergence of the effects of prolonged loud noise exposure and the consumption of MDMA on the same system might explain the sudden fatal events that happen in recreational situations.

How and why environmental noise impacts animals: an integrative, mechanistic review

The scope and magnitude of anthropogenic noise pollution are often much greater than those of natural noise and are predicted to have an array of deleterious effects on wildlife. Recent work on this topic has focused mainly on behavioural responses of animals exposed to noise. Here, by outlining the effects of acoustic stimuli on animal physiology, development, neural function and genetic effects, we advocate the use of a more mechanistic approach in anthropogenic environments. Specifically, we summarise evidence and hypotheses from research on laboratory, domestic and free-living animals exposed to biotic and abiotic stimuli, studied both observationally and experimentally. We hope that this molecular- and cellular-focused literature, which examines the effects of noise on the neuroendocrine system, reproduction and development, metabolism, cardiovascular health, cognition and sleep, audition, the immune system, and DNA integrity and gene expression, will help researchers better understand results of previous work, as well as identify new avenues of future research in anthropogenic environments. Furthermore, given the interconnectedness of these physiological, cellular and genetic processes, and their effects on behaviour and fitness, we suggest that much can be learned from a more integrative framework of how and why animals are affected by environmental noise.

Effects of developmental stress and lead (Pb) on corticosterone after chronic and acute stress, brain monoamines, and blood Pb levels in rats

Despite restrictions, exposure to lead (Pb) continues. Moreover, exposure varies and is often higher in lower socioeconomic status (SES) families and remains a significant risk to cognitive development. Stress is another risk factor. Lower SES may be a proxy for stress in humans. When stress and Pb co-occur, risk may be increased. A few previous experiments have combined Pb with intermittent or acute stress but not with chronic stress. To determine if chronic developmental stress affects outcome in combination with Pb, we tested such effects on growth, organ weight, brain monoamines, and response to an acute stressor. Sprague Dawley rats were gavaged with Pb acetate (1 or 10 mg/kg) or vehicle every other day from postnatal day (P)4-29 and reared in standard or barren cages. Subsets were analyzed at different ages (P11, 19, 29). Chronic stress did not alter blood Pb levels but altered HPA axis response during early development whereas Pb did not. Pb treatment and rearing each altered organ-to-body weight ratios, most notably of thymus weights. Both Pb and rearing resulted in age- and region-dependent changes in serotonin and norepinephrine levels and in dopamine and serotonin turnover. The model introduced here may be useful for investigating the interaction of Pb and chronic developmental stress.

Different stress-related phenotypes of BALB/c mice from in-house or vendor: alterations of the sympathetic and HPA axis responsiveness

Background

Laboratory routine procedures such as handling, injection, gavage or transportation are stressful events which may influence physiological parameters of laboratory animals and may interfere with the interpretation of the experimental results. Here, we investigated if female BALB/c mice derived from in-house breeding and BALB/c mice from a vendor which were shipped during their juvenile life differ in their HPA axis activity and stress responsiveness in adulthood.

Results

We show that already transferring the home cage to another room is a stressful event which causes an increased HPA axis activation for at least 24 hours as well as a loss of circulating lymphocytes which normalizes during a few days after transportation. However and important for the interpretation of experimental data, commercially available strain-, age- and gender-matched animals that were shipped over-night showed elevated glucocorticoid levels for up to three weeks after shipment, indicating a heightened HPA axis activation and they gained less body weight during adolescence. Four weeks after shipment, these vendor-derived mice showed increased corticosterone levels at 45-min after intraperitoneal ACTH challenge but, unexpectedly, no acute stress-induced glucocorticoid release. Surprisingly, activation of monoaminergic pathways were identified to inhibit the central nervous HPA axis activation in the vendor-derived, shipped animals since depletion of monoamines by reserpine treatment could restore the stress-induced HPA axis response during acute stress.

Conclusions

In-house bred and vendor-derived BALB/c mice show a different stress-induced HPA axis response in adulthood which seems to be associated with different central monoaminergic pathway activity. The stress of shipment itself and/or differences in raising conditions, therefore, can cause the development of different stress response phenotypes which needs to be taken into account when interpreting experimental data.

The impact of light, noise, cage cleaning and in-house transport on welfare and stress of laboratory rats

Human interaction and physical environmental factors are part of the stimuli presented to laboratory animals everyday, influencing their behaviour and physiology and contributing to their welfare. Certain environmental conditions and routine procedures in the animal facility might induce stress responses and when the animal is unable to maintain its homeostasis in the presence of a particular stressor, the animal's wellbeing is threatened. This review article summarizes several published studies on the impact of environmental factors such as light, noise, cage cleaning and in-house transport on welfare and stress of laboratory rats. The behaviour and physiological responses of laboratory rats to different environmental housing conditions and routine procedures are reviewed. Recommendations on the welfare of laboratory rats and refinements in experimental design are discussed and how these can influence and improve the quality of scientific data.

The effect of chronic variable stress on bowel habit and adrenal function in rats

BACKGROUND AND AIM

Increased colonic motility is a well-known stress response and corticotropin releasing hormone plays an important role in this response, but sequential change of bowel habit and adrenal function during chronic stress has not been reported. The objective of this study was to evaluate the effect of chronic stress on bowel habit and adrenal function.

METHODS

Male Sprague-Dawley rats were exposed to chronic variable stress (CVS) for 6 weeks. We measured daily the number and weight of pellets and weekly urinary corticosterone. After 6 weeks of experiment, visceromotor response (VMR) to colorectal distention (CRD), serum corticosterone and adrenal glands weight were measured.

RESULTS

The number and weight of pellets in CVS rats was greater than those of the control rats initially and decreased during the later period. However, CVS rats showed continuously exaggerated daily variation of pellet number than control rats to the end of experimental period. Urinary corticosterone was increased in CVS rat until the fifth week, but urine and serum corticosterone were not statistically different between groups at the sixth week. However, the relative weight of adrenal glands was higher in CVS rats at the sixth week. CVS rats showed exaggerated VMR to CRD than the control rats.

CONCLUSIONS

The prolonged and variable stress to rats induced sustained bowel habit dysfunction and visceral hypersensitivity without adaptation. Chronic stress also increased adrenal activity from the early phase and finally caused adrenal hypertrophy with relatively decreased activity. But adrenal change was not parallel to bowel habit change and it remains to be seen whether adrenal dysfunction is directly related to bowel habit dysfunction.

Relationship between stress, eating behavior, and obesity

Stress is thought to influence human eating behavior and has been examined in animal and human studies. Our understanding of the stress-eating relation is confounded by limitations inherent in the study designs; however, we can make some tentative conclusions that support the notion that stress can influence eating patterns in humans. Stress appears to alter overall food intake in two ways, resulting in under- or overeating, which may be influenced by stressor severity. Chronic life stress seems to be associated with a greater preference for energy- and nutrient-dense foods, namely those that are high in sugar and fat. Evidence from longitudinal studies suggests that chronic life stress may be causally linked to weight gain, with a greater effect seen in men. Stress-induced eating may be one factor contributing to the development of obesity. Future studies that measure biological markers of stress will assist our understanding of the physiologic mechanism underlying the stress-eating relation and how stress might be linked to neurotransmitters and hormones that control appetite.

How emotions affect eating: a five-way model

Despite the importance of affective processes in eating behaviour, it remains difficult to predict how emotions affect eating. Emphasizing individual differences, previous research did not pay full attention to the twofold variability of emotion-induced changes of eating (variability across both individuals and emotions). By contrast, the present paper takes into account both individual characteristics and emotion features, and specifies five classes of emotion-induced changes of eating: (1) emotional control of food choice, (2) emotional suppression of food intake, (3) impairment of cognitive eating controls, (4) eating to regulate emotions, and (5) emotion-congruent modulation of eating. These classes are distinguished by antecedent conditions, eating responses and mediating mechanisms. They point to basic functional principles underlying the relations between emotions and biologically based motives: interference, concomitance and regulation. Thus, emotion-induced changes of eating can be a result of interference of eating by emotions, a by-product of emotions, and a consequence of regulatory processes (i.e., emotions may regulate eating, and eating may regulate emotions).

Chronic stress induces adrenal hyperplasia and hypertrophy in a subregion-specific manner

The adrenal gland is an essential stress-responsive organ that is part of both the hypothalamic-pituitary-adrenal axis and the sympatho-adrenomedullary system. Chronic stress exposure commonly increases adrenal weight, but it is not known to what extent this growth is due to cellular hyperplasia or hypertrophy and whether it is subregion specific. Moreover, it is not clear whether increased production of adrenal glucocorticoid after chronic stress is due to increased sensitivity to adrenocorticotropic hormone (ACTH) vs. increased maximal output. The present studies use a 14-day chronic variable stress (CVS) paradigm in adult male rats to assess the effects of chronic stress on adrenal growth and corticosterone steroidogenesis. Exogenous ACTH administration (0-895 ng/100 g body wt) to dexamethasone-blocked rats demonstrated that CVS increased maximal plasma and adrenal corticosterone responses to ACTH without affecting sensitivity. This enhanced function was associated with increased adrenal weight, DNA and RNA content, and RNA/DNA ratio after CVS, suggesting that both cellular hyperplasia and hypertrophy occurred. Unbiased stereological counting of cells labeled for Ki67 (cell division marker) or 4,6-diamidino-2-phenylindole (nuclear marker), combined with zone specific markers, showed that CVS induced hyperplasia in the outer zona fasciculata, hypertrophy in the inner zona fasciculata and medulla, and reduced cell size in the zona glomerulosa. Collectively, these results demonstrate that increased adrenal weight after CVS is due to hyperplasia and hypertrophy that occur in specific adrenal subregions and is associated with increased maximal corticosterone responses to ACTH. These chronic stress-induced changes in adrenal growth and function may have implications for patients with stress-related disorders.

Social defeat and footshock increase body mass and adiposity in male Syrian hamsters

Obesity is a world-wide epidemic, and many factors, including stress, have been linked to this growing trend. After social stress (i.e., defeat), subordinate laboratory rats and most laboratory mice become hypophagic and, subsequently, lose body mass; the opposite is true of subordinate Syrian hamsters. After social defeat, Syrian hamsters become hyperphagic and gain body mass compared with nonstressed controls. It is unknown whether this increase in body mass and food intake is limited to subordinate hamsters. In experiment 1, we asked, do dominant hamsters increase food intake, body mass, and adiposity after an agonistic encounter? Subordinate hamsters increased food intake and body mass compared with nonstressed controls. Although there was no difference in food intake or absolute body mass between dominant and nonstressed control animals, cumulative body mass gain was significantly higher in dominant than in nonstressed control animals. Total carcass lipid and white adipose tissue (WAT) (i.e., retroperitoneal and epididymal WAT) masses were significantly increased in subordinate, but not dominant, hamsters compared with nonstressed controls. In experiment 2, we asked, does footshock stress increase food intake, body mass, and adiposity. Hamsters exposed to defeat, but not footshock stress, increased food intake relative to nonstressed controls. In animals exposed to defeat or footshock stress, body mass, as well as mesenteric WAT mass, increased compared with nonstressed controls. Collectively, these data demonstrate that social and nonsocial stressors increase body and lipid mass in male hamsters, suggesting that this species may prove useful for studying the physiology of stress-induced obesity in some humans.

Effect of chronic psychological stress on insulin release from rat isolated pancreatic islets

Despite documented studies, the exact role of stress on diabetes is still unclear. The present study investigates the effect of chronic psychological stress on insulin release from isolated rat pancreatic islets. Male Wistar rats were divided into two groups of control and stressed (n=8/group). The animals of the stressed group were exposed to restraint stressors (1 h twice daily) for 15 or 30 consecutive days. At the beginning and end of the experimental periods, the animals were weighed and blood samples taken to determine the fasting plasma levels of glucose, insulin and corticosterone. On the following day the pancreatic islets of 5/group of the above animals were isolated and the static release of insulin in the presence of different glucose concentrations (2.8, 5.6, 8.3, 16.7 mM) was assessed. The results showed that in the stressed group, fasting plasma glucose levels were increased significantly on the 15th day as compared to the control group. However there was no significant increase on the 30th day. Fasting plasma insulin was significantly decreased on the 15th and 30th days of the experiment in the stressed group. Stressed rats showed significantly higher fasting plasma corticosterone levels, only on the 15th day, as compared to the control rats. In response to increasing concentrations of glucose, insulin release from islets of the stressed group was increased significantly on the 30th day of the experiment as compared to the control group. We conclude that chronic psychological stress could increase responsiveness of pancreatic beta cells to glucose, in vitro, and thus, low insulin levels of the stressed animals, in vivo, may be due to reason(s) other than the reduction of insulin releasing capacity of pancreatic beta cells.

Involvement of cholecystokininergic systems in anxiety-induced hyperalgesia in male rats: behavioral and biochemical studies

Keeping in mind the increased pain complaints reported in anxious or depressive patients, our goal was to investigate in rats the consequences of an experimentally provoked state of anxiety/depression on pain behavior and on its underlying mechanisms. We therefore used a model of social defeat consisting of a 30 min protected confrontation followed by a 15 min physical confrontation, repeated during 4 d, that elicited symptoms close to those observed in humans with anxiety or depression. Indeed, 5 d later, animals subjected to social-defeat confrontation were characterized by a decrease of sweet-water consumption and of body weight, and a hyperactivity of the hypothalamic-pituitary-adrenal axis, suggesting that the social-defeat procedure induced a prolonged state of anxiety. Rats subjected to the social-defeat procedure showed an enhanced nociceptive behavior to the subcutaneous administration of formalin, 5 d after the last confrontation session. Because chronic treatment with the established anxiolytic chlordiazepoxide (10 mg.kg(-1).d(-1)) prevented hyperalgesia, this strongly suggested that this experimental procedure might be a suitable animal model of "anxiety-induced hyperalgesia." Hyperalgesia associated with anxiety not only was related to a significant increase of CCKLM [cholecystokinin (CCK)-like material] in frontal cortex microdialysates but also was prevented by a CCK-B receptor antagonist [4-[[2-[[3-(1H-indol-3-yl)-2-methyl-1-oxo-2[[(tricyclo[3.3[12,17]dec-2-yloxy)-carbonyl]amino]-propyl]amino]-1-phenyethyl]amino]-4-oxo-[R-(R*, R*)]-butanoate N-methyl-D-glucamine (CI-988)] (2 mg/kg), strongly supporting the involvement of central CCKergic systems in these phenomena. Finally, combined treatments with CI-988 and morphine completely suppressed pain-related behavior, supporting the idea that the association of both compounds might represent a new therapeutic approach to reduce the increase of pain complaints highly prevalent among anxious or depressive patients.

Exposure to chronic noise and fractionated X-ray radiation elicits biochemical changes and disrupts body weight gain in rat

The aim was to assess the developmental and biochemical effects resulting from separate and combined exposures to radiation and noise in adult male Sprague-Dawley rats. For 21 days, animals were exposed daily (1) to whole-body 121 kVp X-ray exposure (cumulative dose=5 Gy), (2) to random intermittent noise band-limited between 0.4 and 20 kHz; 2 h day(-1) 86 decibels (dB) and (3) to combined exposures. Control animals were housed under ambient noise conditions 55 dB A-weighted (dBA) and sham-exposed to X-rays. Body weight gain was significantly reduced in animals exposed to either X-rays or noise, and the loss was more pronounced in animals exposed to both conditions. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone was altered by the treatment conditions. This study corroborated previous reports that ionizing radiation exposure increased plasma levels of 8-hydroxy-2'-deoxyguanosine (8-OHDG), but no effect was observed in animals co-exposed to chronic noise. Plasma big-endothelin-1 (Big ET-1) was significantly reduced in animals exposed to a combination of noise and X-rays. The results indicated that (1) adaptation to chronic noise appeared to occur at the level of the hypothalamic pituitary adrenal (HPA) response, in spite of a compromise in overall body weight gain; and (2) ionizing radiation exposure might alter systems activated by stressor exposure and/or act independently to influence health outcomes.

Emotionsbedingtes Essverhalten: Die Bedeutung der Emotionen

Zusammenfassung. Wirkungen von Emotionen auf das Essverhalten variieren in Abhängigkeit von Person- und Emotionsmerkmalen. Bisherige Untersuchungen waren größtenteils auf den Einfluss von Personmerkmalen gerichtet. Sie zeigten, dass ein gezügelter sowie ein emotionaler Ess-Stil zu gesteigerter Nahrungsaufnahme bei negativen Emotionen prädisponieren. Weitere Untersuchungen verweisen auf den Einfluss von Emotionsmerkmalen wie Intensität und Valenz. Der vorliegende Beitrag fasst den Forschungsstand zusammen und unterteilt die Wirkungen von Emotionen auf das Essverhalten in fünf Varianten, die sich durch definierte Person- und Emotionsmerkmale vorhersagen lassen: emotionale Steuerung der Nahrungswahl, emotionale Hemmung des Essverhaltens, emotionale Enthemmung gezügelten Essverhaltens, emotional-instrumentelles Essverhalten und emotionkongruente Modulation des Essverhaltens.

Effects of loud noise exposure on DNA integrity in rat adrenal gland

Loud noise is generally considered an environmental stressor causing negative effects on acoustic, cardiovascular, nervous, and endocrine systems. In this study, we investigated the effects of noise exposure on DNA integrity in rat adrenal gland evaluated by the comet assay. The exposure to loud noise (100 dBA) for 12 hr caused a significant increase of DNA damage in the adrenal gland. Genetic alterations did not decrease 24 hr after the cessation of the stimulus. We hypothesize that an imbalance of redox cell status is responsible for the induction and persistence of noise-induced cellular damage.

Effects of loud noise exposure on mouse myocardium: a comparison with the rat

Loud noise is an environmental stressor of everyday life, which affects different organs and apparati, in particular the cardiovascular system. We have already reported that noise exposure produces significant alterations in the rat myocardium, consisting of mitochondrial damage, which is evident as lysis of the cristae and dilution of the matrix. Since there are high similarities between mouse and human species, the aim of our study was to investigate the effects of acute noise exposure on the mouse heart. We found that noise exposure affects mouse myocardium at similar subcellular sites to those already described in the rat; nonetheless, quantitative analysis of the percentage of altered mitochondria in both species disclosed a clear difference between mouse and rat myocardium, which strongly suggests a different sensitivity to noise stimulus. We hypothesize that the species differences on the extent of myocardial alterations here observed might be due to the zonal pattern of cardiac noradrenergic receptors, which should be the final effectors for noise-induced myocardial changes.

Morphological alterations induced by loud noise in the myocardium: the role of benzodiazepine receptors

Noise represents an environmental stress factor affecting several organs and apparati, including the cardiovascular system. In experimental animals undergoing noise exposure, subcellular myocardial changes have been reported, especially at mitochondrial level; in particular, after 6 hours of exposure only the atrium exhibited significant mitochondrial alterations, whereas after 12 hours as well as subchronic exposure both atrium and ventricle were damaged. The first part of the present article overviews the experimental evidence on effects of noise on the myocardium. In the second part, the review analyzes the role of benzodiazepine receptors and the potential efficacy of benzodiazepine ligands in preventing the mitochondrial damage induced by noise exposure. Drugs acting at both central and peripheral benzodiazepine receptors significantly prevent this damage. Differences in the amount and the duration of the protective effect might depend on variability in the potency and pharmacokinetics of the specific drug. The effects of the combined treatment with selective and non-selective peripheral benzodiazepine ligands on noise stimulation are discussed at biochemical level reviewing studies on the effects of noise exposure on mitochondrial fractions.

Rats fed only during the light period are resistant to stress-induced weight loss

Repeated restraint stress (3 h/day for 3 days) causes a chronic down-regulation of body weight in rats. This study determined whether weight loss was influenced by the time of day that rats had access to food or that stress was applied. Groups of male Sprague-Dawley rats were fed a 40% kcal fat diet with food given ad libitum, only during the light phase or only during the dark phase. After 2 weeks of adaptation, rats within each feeding treatment were divided into four groups. One was exposed to repeated restraint at the start of the light phase, another was restrained at the start of the dark phase and the remaining groups were nonstressed controls for restrained rats. Body weight was significantly reduced in ad libitum- and dark-fed restrained rats, compared with nonstressed controls, from Day 2 of restraint, regardless of the time of day that they were stressed. There was no significant effect of restraint on weight change of light-fed rats. Food intake was inhibited by stress in ad libitum- and dark-fed rats, but it was not changed in light-fed rats. Serum corticosterone was increased by restraint in all rats irrespective of feeding schedule. This study demonstrates that stress-induced weight loss only occurs when rats have food available during their normal feeding period (dark phase) and is not determined by increased corticosterone release.

Brief and repeated noise exposure produces different morphological and biochemical effects in noradrenaline and adrenaline cells of adrenal medulla

Exposure to stressful stimuli is known to activate the peripheral sympathetic nervous system and the adrenal gland. In this study, we evaluated the effects of single or repeated bouts of exposure to a readily measurable stressful stimulus (loud noise) on the catecholamine content and ultrastructure of the rat adrenal medulla. In particular, we measured tissue levels of dopamine, noradrenaline, adrenaline and metabolites. In parallel studies, we evaluated the fine ultrastructure of catecholamine cells, including a detailed study of catecholamine granules and a morphometric analysis of adrenaline and noradrenaline medullary cells. Animals were exposed either to a single (6 h) session of loud (100 dBA) noise, or to this noise stimulus repeated every day for 21 consecutive days. There was a marked correlation between biochemical indexes of catecholamine activity and the ultrastructural morphometry of specific catecholamine granules. Exposure to loud noise for 6 h induced a parallel increase in dopamine, noradrenaline, adrenaline and their metabolites, a polarization and an increased numerical density of noradrenaline and adrenaline granules in the cells. After repeated noise exposure, noradrenaline levels were significantly higher than in controls, and adrenaline decreased significantly. In addition, adrenaline cells also exhibited ultrastructural alterations consisting of wide homogeneous cytoplasmic areas and large, pale vesicles.

Accelerative effect of olive oil on liver glycogen synthesis in rats subjected to water-immersion restraint stress

The effects of dietary oils on stress-induced changes in the liver glycogen metabolism of male Wistar rats at 6 weeks of age were investigated. The rats were subjected to repetitive water-immersion restraint and fed with a 20% saturated fatty acid mixture (PSC), olive oil (OLI), safflower oil (SAF), or linseed oil (LIS) diet. Stress loading decresed the body weight gain, although the food intake was hardly changed, and the weights of the liver and spleen generally declined regardless of the elapsed time after stress loading and the type of dietary oil. The adrenal weight was generally enhanced by stress in all deitary groups, and particularly tended to be greater in the OLI and PSC groups than in the other two. The plasma corticosterone concentration increased immediately after stressing (Stress-1), but approached the level of the rats with no stress (No stress) 2 h after releasing the stress load (Stress-2) in all groups. The enhancement of corticosterone level in the Stress-1 animals was large in the PSC and OLI groups, and the decline of this level in the Stress-2 animals was small in the OLI group when compared with the other groups. Although the concentrations of total cholesterol (T-CHOL) and triacylglycerol (TG) in the plasma were decreased by stress loading in all groups, these concentrations in the PSC and OLI groups were nearly always higher than in the other groups. The liver serine dehydratase (SDH) activity enhanced by stress was high in the OLI group and tended to be high in the PSC group when compared with the other groups. The contents of liver glycogen were reduced in the Stress-1 animals and extremely elevated in the Stress-2 animals of all groups, and particularly in the OLI group, the reduction in the Stress-1 animals was smaller and the enhancement in the Stress-2 animals was greater than in the other groups. These results suggest that feeding oleic acid to rats exposed to water-immersion restraint further accelerated liver glycogen synthesis through the rise in liver SDH activity due to increased corticosterone secretion when compared with the effect from linoleic and alpha-linolenic acids.

Effect of noise exposure on rat cardiac peripheral benzodiazepine receptors

Noise is an environmental physical agent, which is regarded as a stressful stimulus: impairment and modifications in biological functions are reported, after loud noise exposure, at several levels in human and animal organs and apparatuses, as well as in the endocrine, cardiovascular and nervous system. In the present study equilibrium binding parameters of peripheral benzodiazepine receptors (PBRs) labelled by the specific radioligand [3H]PK 11195, were evaluated in cardiac tissue of rats submitted to 6 or 12 h noise exposure and of rats treated "in vivo" with PBR ligands such as PK 11195, Ro54864, diazepam and then noise-exposed. Results revealed a statistically significant decrease in the maximum number of binding sites (Bmax) of [3H]PK 11195 in atrial membranes of 6 or 12 h noise exposed rats, compared with sham-exposed animals, without any change in the dissociation constant (Kd). The "in vivo" PBR ligand pre-treatment counteracted the noise-induced modifications of PBR density. As PBRs are mainly located on mitochondria we also investigated whether noise exposure can affect the [3H]PK 11195 binding parameters in isolated cardiac mitochondrial fractions. Results indicated a significant Bmax value decrease in right atrial mitochondrial fractions of rats 6 or 12 h noise-exposed. Furthermore, as PBR has been suggested to be a supramolecular complex that might coincide with the not-yet-established structure of the mitochondrial permeability transition (MPT)-pore, the status of the MPT-pore in isolated heart mitochondria was investigated in noise- and sham-exposed rats. The loss of absorbance associated with the calcium-induced MPT-pore opening was greater in mitochondria isolated from hearts of 6 h noise- than those of sham-exposed rats. In conclusion, these findings represent a further instance for PBR density decrease in response to a stressful stimulus, like noise; in addition they revealed that "in vivo" administration of PBR ligands significantly prevents this decrease. Finally, our data also suggest the involvement of MPT in the response of an organism to noise stress.

Social stability attenuates the stress in the modified multiple platform method for paradoxical sleep deprivation in the rat

The instrumental methods to induce paradoxical sleep (PS) deprivation are stressful. The modified multiple platform method (MMPM), in which animals are placed with new cohorts inside the water tanks, results in augmented ACTH and corticosterone (CORT) responses. We hypothesised that this increased response could be attributed to social instability. In addition, we tested a new environmental control, a grid (GR) placed on the tank floor. Animals were submitted to the MMPM for 4 days as socially unstable (UG--coming from several cages) or stable groups (SG--coming from one cage), placed either on narrow platforms or on the grid. All UG animals presented higher ACTH levels than their SG counterparts, including home-cage controls. CORT levels of manipulated animals were higher than controls only in the stable group. UG animals presented heavier adrenals than their SG counterparts. Only adrenals from SG animals placed on the grid were similar to cage controls. SG rats lost less weight than UG animals. While UG animals ate the same amount of chow as home-cage controls, SG animals ate more than control and UG animals. These results suggest that the stress of the MMPM can be attenuated in stable groups. The introduction of a grid on the tank floor may serve an adequate environmental control as far as stress-related variables are considered.

The effects of changes in housing on feeding and wheel running

The experiments explored the effects on feeding when rats were moved between individual and paired housing. In Experiment 1, rats moved to paired housing showed a 3-day suppression in feeding (initially 23%) compared to chronically individual- or pair-housed rats. In Experiment 2, half of the rats from the two control groups of Experiment 1 were moved between individual and paired housing on alternate days. Only the rats moved to paired housing showed a feeding suppression (initially 40%), but the nature of the suppression differed from Experiment 1: it appeared that only one rat of each pair showed a feeding suppression. Experiment 3 examined simultaneous introduction of running wheels and moves to paired housing. The feeding suppression induced by the move to paired housing was more immediate and shorter lived than the wheel-induced suppression. Unlike wheel access, paired housing produced only a temporary suppression of body weight. These experiments suggest that the relatively simple manipulation of moving rats from individual to paired housing results in a temporary stress-induced decrease in feeding.