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The negative emotional consequences associated with life stress exposure in an individual can affect the emotional state of social partners. In this study, we describe an experimental rat model of social stress contagion and its effects on social behaviour and cardiac autonomic and neuroendocrine functions. Adult male Wistar rats were pair-housed and one animal (designated as “demonstrator” (DEM)) was submitted to either social defeat stress (STR) by an aggressive male Wild-type rat in a separate room or just exposed to an unfamiliar empty cage (control condition, CTR), once a day for 4 consecutive days. We evaluated the influence of cohabitation with a STR DEM on behavioural, cardiac autonomic and neuroendocrine outcomes in the cagemate (defined “observer” (OBS)). After repeated social stress, STR DEM rats showed clear signs of social avoidance when tested in a new social context compared to CTR DEM rats. Interestingly, also their cagemate STR OBSs showed higher levels of social avoidance compared to CTR OBSs. Moreover, STR OBS rats exhibited a higher heart rate and a larger shift of cardiac autonomic balance toward sympathetic prevalence (as indexed by heart rate variability analysis) immediately after the first reunification with their STR DEMs, compared to the control condition. This heightened cardiac autonomic responsiveness habituated over time. Finally, STR OBSs showed elevated plasma corticosterone levels at the end of the experimental protocol compared to CTR OBSs. These findings demonstrate that cohabitation with a DEM rat, which has experienced repeated social defeat stress, substantially disrupts social behaviour and induces short-lasting cardiac autonomic activation and hypothalamic-pituitary-adrenal axis hyperactivity in the OBS rat, thus suggesting emotional state-matching between the OBS and the DEM rats. We conclude that this rodent model may be further exploited for investigating the neurobiological bases of negative affective sharing between social partners under chronic social stress conditions. [ABSTRACT FROM AUTHOR]

Although millions of cats live among humans worldwide the scientific community knows relatively little about cat behavior and cognition. Olfaction is an important perceptual sense for many members of Carnivora, however the role of chemical signals in cat social relationships is not fully understood. Research indicates chemical signals play an important role in many areas of cat behavior including mother-offspring and conspecific interactions and exploration of their environment. Chemical cues appear to play a role in stress and anxiety reduction, allowing cats to feel secure in their environment. A better understanding of cat chemical signals, especially as it relates to within and between species communication, may lead to an increase in cat wellbeing as humans can utilize this knowledge in applied settings. Therefore, the purpose of this review is to investigate how cats process and use chemical signals in social contexts and identify ways this information can be applied to address cat behavioral issues, such as inappropriate litter box and scratching behavior, and improve cat welfare, including species-appropriate ways of reinforcing the human-cat bond. [ABSTRACT FROM AUTHOR]

Due to their direct inaccessibility, affective states are classically assessed by gathering concomitant physiological and behavioral measures. Although such a dual approach to assess emotional states is frequently used in different species including humans, the invasiveness of procedures for physiological recordings particularly in smaller-sized animals strongly restricts their application. We used infrared thermography, a non-invasive method, to assess physiological arousal during open field and elevated plus maze tests in mice. By measuring changes in surface temperature indicative of the animals' emotional response, we aimed to improve the inherently limited and still controversial information provided by behavioral parameters commonly used in these tests. Our results showed significant and consistent thermal responses during both tests, in accordance with classical physiological responses occurring in stressful situations. Besides, we found correlations between these thermal responses and the occurrence of anxiety-related behaviors. Furthermore, initial temperatures measured at the start of each procedure (open field, elevated plus maze), which can be interpreted as a measure of the animals' initial physiological arousal, predicted the levels of activity and of anxiety-related behaviors displayed during the tests. Our results stress the strong link between physiological correlates of emotions and behaviors expressed during unconditioned fear tests. [ABSTRACT FROM AUTHOR]

Inflammatory bowel disease is associated with an increased risk of mental disorders and can be exacerbated by stress. In this study which was performed with male 10-week old C57Bl/6N mice, we used dextran sulfate sodium (DSS)-induced colitis to evaluate behavioral changes caused by intestinal inflammation, to assess the interaction between repeated psychological stress (water avoidance stress, WAS) and colitis in modifying behavior, and to analyze neurochemical correlates of this interaction. A 7-day treatment with DSS (2% in drinking water) decreased locomotion and enhanced anxiety-like behavior in the open field test and reduced social interaction. Repeated exposure to WAS for 7 days had little influence on behavior but prevented the DSS-induced behavioral disturbances in the open field and SI tests. In contrast, repeated WAS did not modify colon length, colonic myeloperoxidase content and circulating proinflammatory cytokines, parameters used to assess colitis severity. DSS-induced colitis was associated with an increase in circulating neuropeptide Y (NPY), a rise in the hypothalamic expression of cyclooxygenase-2 mRNA and a decrease in the hippocampal expression of NPY mRNA, brain-derived neurotrophic factor mRNA and mineralocorticoid receptor mRNA. Repeated WAS significantly decreased the relative expression of corticotropin-releasing factor mRNA in the hippocampus. The effect of repeated WAS to blunt the DSS-evoked behavioral disturbances was associated with a rise of circulating corticosterone and an increase in the expression of hypothalamic NPY mRNA. These results show that experimental colitis leads to a particular range of behavioral alterations which can be prevented by repeated WAS, a model of predictable chronic stress, while the severity of colitis remains unabated. We conclude that the mechanisms underlying the resilience effect of repeated WAS involves hypothalamic NPY and the hypothalamic-pituitary-adrenal axis. [ABSTRACT FROM AUTHOR]

This study investigated the influence of neonatal handling on behavioral and biochemical consequences of chronic mild stress (CMS) in adulthood. Male rat pups were submitted to daily tactile stimulation (TS) or maternal separation (MS), from postnatal day 1 (PND1) to postnatal day 21 (PND21), for 10 min/day. In adulthood, half the number of animals were exposed to CMS for 3 weeks and submitted to behavioral testing, including sucrose preference (SP), elevated plus maze (EPM), and defensive burying tasks (DBTs), followed by biochemical assessments. CMS reduced SP, increased anxiety in EPM and DBT, and increased adrenal weight. In addition, CMS decreased plasma vitamin C (VIT C) levels and increased protein carbonyl (PC) levels, catalase (CAT) activity in hippocampus and cortex, and superoxide dismutase (SOD) levels in cortex. In contrast, both forms of neonatal handling were able to prevent reduction in SP, anxiety behavior in DBT, and CMS-induced adrenal weight increase. Furthermore, they were also able to prevent plasma VIT C reduction, hippocampal PC levels increase, CAT activity increase in hippocampus and cortex, and SOD levels increase in cortex following CMS. Only TS was able to prevent CMS-induced anxiety symptoms in EPM and PC levels in cortex. Taken together, these findings show the protective role of neonatal handling, especially TS, which may enhance ability to cope with stressful situations in adulthood. [ABSTRACT FROM AUTHOR]

Leptin, originally identified as an anti-obesity hormone, also has an important role in the regulation of mood and emotion. The present study was designed to monitor effects of injected leptin on immobilization stress-induced anorexia, behavioral deficits, and plasma corticosterone secretion in rats. Exposure to 2 h immobilization stress decreased food intake and body weight in saline-injected animals. Animals exposed to open field, elevated plus maze, and light-dark transition tests the day following immobilization exhibited anxiety-like behavior. Leptin injected at doses of 0.1 and 0.5 mg/kg also decreased food intake and body weight in unstressed animals and elicited anxiolytic effects at dose of 0.5 mg/kg, monitored on the following day. Immobilization-induced decreases in food intake, body weight, as well as stress-induced behavioral deficits in the open field, elevated plus maze, and light-dark transition test were reversed by exogenous leptin in a dose-dependent (0.1-0.5 mg/kg) manner. Acute exposure to 2 h immobilization produced a fourfold rise in plasma levels of corticosterone. Animals injected with leptin at a dose of 0.1 mg/kg, but not at dose of 0.5 mg/kg, exhibited a marginal increase in plasma corticosterone. Immobilization-induced increases of plasma corticosterone were reversed by leptin injected at doses of 0.1 or 0.5 mg/kg. The data suggest that exogenous leptin can reduce stress perception, resulting in an inhibition of stress effects on the activity of hypothalamic-pituitary-adrenal axis and behavior. The reported pharmacological effects of leptin represent an innovative approach for the treatment of stress-related disorders. [ABSTRACT FROM AUTHOR]

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Abstract: Several studies have shown that the α1-adrenoreceptor is involved in controlling extracellular serotonin levels. The administration of the α1-adrenoreceptor antagonist prazosin was shown to decrease extracellular serotonin levels in the hippocampus, the prefrontal cortex and the raphe nucleus, while the administration of the α1-adrenoreceptor agonist cirazoline was shown to increase serotonin levels. Furthermore, the elevation of serotonin levels induced by the selective serotonin reuptake inhibitor (SSRI) citalopram was attenuated by prazosin. Thus, α1-adrenoreceptor antagonists may affect SSRI-induced increases in extracellular serotonin levels and their antidepressive and anxiolytic effects. However, little is known about the influence of α1-adrenoreceptor antagonists on the behavioral pharmacological effects of SSRIs. The conditioned fear stress-induced freezing behavior is an animal model of anxiety and can detect the anxiolytic effect of SSRIs. To clarify whether an α1-adrenoreceptor antagonist affects the anxiolytic action of SSRIs, we examined the effects of the co-administration of the α1-adrenoreceptor antagonist prazosin and the SSRI citalopram using the contextual conditioned fear stress model. Low-dose prazosin (0.03mg/kg) significantly attenuated the citalopram (3mg/kg)-induced decrease in conditioned freezing. Moreover, high-dose (0.5mg/kg), but not low-dose (0.03mg/kg), prazosin significantly attenuated citalopram (10mg/kg)-induced decreases in conditioned freezing. These drugs did not affect the spontaneous motor activity of the rats. Therefore, these results suggest that blocking the α1-adrenoreceptor decreases the anxiolytic effect of citalopram. [Copyright &y& Elsevier]

Abstract: The objectives of this study were to evaluate the effects of a diet (CALM CANINE) supplemented with alpha-casozepine and L-tryptophan on the stress response of anxious dogs with a focus on anxiety-related behavioral parameters and physiological parameters. Forty-four privately owned dogs were first fed with the control diet, followed by the study diet, each for an 8-week period, with a transitional period of 1 week between the diets. After 7 weeks on a particular diet, owners reported their dogs'' behavior by filling out a questionnaire. Using the Canine Behavioral Assessment and Research Questionnaire, the effect of the study diet was found to be significant for 4 anxiety-related behavioral parameters, possibly mirroring a placebo effect. After 7 weeks on each diet, the urine cortisol-to-creatinine ratio (UCCR) was measured to assess the stress response to a visit to a veterinary practice for toenail clipping. UCCR was measured to complement the interpretation of behavioral data with regard to the stress susceptibility of the dogs. A positive correlation was found between baseline UCCR, as measured in the home situations, and poststressor UCCR. The stressor-induced increase was significantly lower in the dogs when they were fed the study diet than earlier when they were fed the control diet. The supplementation of casozepine or the proportion of protein in a given diet could have been a determining factor. The study diet seems to improve the ability of an individual to cope with stress and may reduce anxiety-related behavior in anxious dogs. [Copyright &y& Elsevier]

Abstract: Depressive and anxiety symptoms experienced by children have often been attributed to normative age-related mood disturbances. In the last decade, early-onset of affective illness has been recognized as a major public health problem. The current study utilized exposure to juvenile stress, which was previously shown to have long-term effects into adulthood in male rats, to compare early to adulthood consequences of juvenile stress on anxiety indices and exploratory behavior in the open field and elevated plus maze. Furthermore, both male and female rats were examined, and in addition, the role of corticosterone as a potential mediator of some of these effects in juvenility and in adulthood, was assessed. Experiments 1–2 examined in male and female rats immediate and long-term behavioral effects of juvenile stress. Experiment 3 assessed circulating corticosterone (CORT) levels, and in experiment 4 male and female rats were injected i.p. with CORT, in either juvenility or in adulthood, to examine whether CORT could mimic the effects of juvenile stress. As expected, in adulthood, juvenile stress resulted in reduced exploratory behavior and reduced exploration of high-risk areas of the mazes. A similar pattern was found in both males and females. In contrast, a reversed behavioral pattern was found in juvenility in both male and female rats, although detailed differences were found between sexes. The application of CORT induced a similar reversed behavioral pattern in juvenile and adult rats of both sexes. Thus, the juvenile stress model might serve as an animal model for studying early-onset of affective illness. [ABSTRACT FROM AUTHOR]

Abstract: The progression and development of multiple sclerosis (MS) has long been hypothesized to be associated with stress. Benzodiazepines have been observed to reduce negative consequences of stress on the immune system in experimental and clinical models, but there are no data on their effects on MS, or experimental autoimmune encephalomyelitis (EAE), a model for human MS. We designed experiments conducted to ascertain whether alprazolam could modify the clinical, histological and neuroendocrine manifestations of acute EAE in Lewis rats exposed to a chronic auditory stressor. EAE was induced by injection of an emulsion of MBP and complete Freund''s adjuvant containing Mycobacterium tuberculosis H37Ra. Stress application and treatment with drugs (placebo or alprazolam) were initiated 5days before inoculation and continued daily for the duration of the experiment (days 14 or 34 postinoculation).Our results show significant increases in the severity of neurological signs, the histological lesions of the spinal cord (inflammation), and the corticosterone plasmatic levels in stressed rats compared to those non-stressed ones. Treatment with alprazolam reversed the adverse effects of stress. These findings could have clinical implications in patients suffering from MS treated with benzodiazepines, so besides the psychopharmacological properties of alprazolam against stress, it has beneficial consequences on EAE. [Copyright &y& Elsevier]

The article presents the results of a study on the use of a reciprocal hybrid model of mice to compare the anxiety behavior between parents and their offspring. According to the authors, inbred male mice demonstrated intensive parental behavior toward their offsprings, particularly parental contact behavior, and their licking/grooming behavior was dependent on the female mice strain they were paired with. They add that the BALB/c model of mice illustrated minimal parental contact behavior than the C57BL/6 model of mice. They indicate that BALB/c male and female mice have higher anxiety behavior than C57BL/6 pairs.

Abstract: Ovarian hormones exert anti-depressive and anxiolytic actions. In this study we have analyzed the effects of ovariectomy on the development of anxiety and depression-like behaviors and on cell proliferation in the hippocampus of mice submitted to chronic unpredictable stress. Animals submitted to stress 4months after ovariectomy showed a significant increase in immobility behavior in the forced swimming test compared to animals submitted to stress 2weeks after ovariectomy. In addition, long-term ovariectomy resulted in a significant decrease on the time spent in the open arms in the elevated plus-maze test compared to control animals. Stress did not significantly affect cell proliferation in the hilus of the dentate gyrus. However, ovariectomy resulted in a significant decrease in cell proliferation. These results indicate that long-term deprivation of ovarian hormones enhances the effect of chronic unpredictable stress on depressive- and anxiety-like behaviors in mice. Therefore, a prolonged deprivation of ovarian hormones may represent a risk factor for the development of depressive and anxiety symptoms after the exposure to stressful experiences. [Copyright &y& Elsevier]

Abstract: The purpose of this randomized, double-blind, placebo-controlled trial was to evaluate the efficacy of a diet containing caseinate hydrolysate (CH) on signs of stress in 2 groups of dogs (defined as Anxious and Nonanxious), using physiological (serum cortisol and lysozyme, N:L ratios and heart rate) and behavioral parameters. From an initial group of 40 female Beagle dogs, ranging in age from 10 months to 4 years (mean = 1.47 years; SD = 0.53) belonging to a dog colony, 32 were selected for this study according to their level of anxiety. A group of 16 Anxious dogs and a group of 16 Nonanxious dogs were identified. A baseline period, aimed to obtain reference values of investigated parameters, preceded the experimental phase. Both groups (Anxious and Nonanxious) were divided into a treatment group, which received the diet containing CH, and a control group which received a placebo diet (PD). Anxious CH and PD groups were balanced for anxiety level. Each dog was evaluated 3 times a day at 4 weeks intervals (T1-T2-T3). Each evaluation lasted 2 days and involved a Reactivity Evaluation Form, a blood sampling, heart rate recording, and a 10-minute behavioral video recording. Results from Reactivity Evaluation Form scores showed that although at T1 Anxious dogs had significantly higher scores (Mann–Whitney test, P < 0.001) compared with Nonanxious dogs, no difference was found between Anxious dogs fed with CH diet and Nonanxious fed with PD or CH diet at T3. Behavioral observations evidenced some signs of improvement in Anxious dog fed with CH diet. Cortisol level significantly decreased in Anxious dogs fed with CH diet (Friedman test, P < 0.05). Individual differences in physiological measures of stress responses may have contributed to the large variability, making interpretation of these measures difficult. These results suggest that CH may be used as a functional ingredient alleviating stress in dogs. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, voles were exposed to owl attack as a group, with their cage mates and in their familiar cages. The anxiety level of each vole was assessed using two parameters: time spent in the open arm of an elevated plus maze; and time spent away from the walls of an open field. Each parameter was measured 24h before and after the group exposure to the owls. We found that the large individual differences in the voles’ behavior measured before exposure to the owls were significantly reduced following exposure. In other words, after exposure all individual voles began to behave the same both in the elevated plus maze and in the open field. This response, as measured 24h after the exposure to the owls, differs from past studies, where individual voles diverge in their immediate response in order to confuse the attacking owl. We suggest that the present finding on reduction in individual differences is a group effect reminiscent of the social response seen in humans following a disaster, when a uniform behavioral code dominates and trims down behavioral variability. [Copyright &y& Elsevier]

Background. Most epidemiological studies report higher prevalence rates of stress-related disorders such as acute stress disorder, post-traumatic stress disorder (PTSD) and major depressive disorder in women than in men. Few animal models of PTSD have taken gender differences into account and have typically used male subjects. In order to explore gender-related PTSD-like stress-responses more thoroughly, we applied an animal model that focuses selectively on individual patterns of behavioural responses. Methods. Prevalence rates of individual behavioural response to a single exposure to predator scent stress (PSS) were assessed by both elevated plus-maze and startle response paradigms. Prevalence rates of extreme behavioural disruption (EBR) on both tests were assessed, correlated to corticosterone levels, and compared to global population response data. In addition, we assessed learning and memory in the Morris water-maze (MWM). Results. There were no significant differences between the behavioural responses related to oestrous cycle phase in terms of global data for the groups or in terms of prevalence rates of EBR. The overall patterns of response of males and females were affected, yet females demonstrated greater levels of baseline anxiety-like behaviour and lower peak levels of post-exposure anxiety-like behaviour than males. However, the prevalence rates of individual subjects who responded with PTSD-like behaviour were equal for female and male subjects. PSS-exposed female subjects demonstrated significantly compromised performance in the MWM compared to males. Conclusions. In this animal model, the results clarified that the assumption that females are more vulnerable is true for the magnitude of the response, but not for the prevalence of pathological response patterns in rat populations. [ABSTRACT FROM AUTHOR]

Abstract: Anxiety has been proposed to play a role in the development of alcohol addiction, but the exact mechanisms by which this occurs remain unclear. The present study aimed to verify the relationship between basal anxiety levels, the anxiolytic-like effect of ethanol, and ethanol intake in mice exposed to an addiction model. In one experiment Swiss mice were characterized as high-anxiety (HA), medium-anxiety (MA), or non-anxiety (NA) in the elevated plus maze and then received saline or ethanol 2 g/kg acutely and chronically and were again exposed to the same test. NA mice decreased while MA mice maintained anxiety indices over the test days, regardless of treatment. HA ethanol-treated mice showed an anxiolytic-like effect, both acutely and chronically, while the saline-treated ones maintained their basal anxiety levels. In another experiment HA and MA mice were exposed to an addiction model based on a 3-bottle free-choice paradigm (ethanol 5% and 10%, and water) consisting of four phases: acquisition (10 weeks), withdrawal (W, 2 weeks), reexposure (2 weeks), and quinine-adulteration (2 weeks). HA and MA control mice had access only to water. Mice were characterized as addicted, heavy-drinker and light-drinker [Fachin-Scheit DJ, Ribeiro AF, Pigatto G, Goeldner FO, Boerngen-Lacerda R. Development of a mouse model of ethanol addiction: naltrexone efficacy in reducing consumption but not craving. J Neural Transm 2006;113:1305–21.]. No difference was observed between HA and MA mice in their preference for and intake of ethanol. No correlation was observed between ethanol intake, during any phase, and anxiety indices measured in the basal tests and during the W phase. The differences in anxiety indices between HA and MA groups persisted in the test performed during ethanol withdrawal, suggesting a “trait” anxiety profile. The data suggest that despite the fact that high anxiety trait levels are important for the anxiolytic-like effects of ethanol, they are not a determining factor for high ethanol intake, at least not under these experimental conditions. [Copyright &y& Elsevier]