Fecal corticosteroids in agouti and non-agouti deer mice (Peromyscus maniculatus)

Total and per gram fecal corticosteroid concentrations were determined for agouti and non-agouti deer mice (Peromyscus maniculatus gracilis) over 24 h under normal caging conditions and after exposure to the stress of novel caging. Per gram corticosteroid concentrations, fecal output, and 24-h corticosteroid production were greater in stressed compared with unstressed deer mice of both color morphs, whereas stressed agoutis had a greater increase in per gram corticosteroid concentrations when compared with non-agoutis. However, due to increased fecal output, stressed non-agouti deer mice had greater 24-h corticosteroid production. Thus, agouti and non-agouti deer mice differ in their hormonal reaction to stress. This is the first demonstration of corticosteroid differences associated with the agouti locus.     

Enhanced pelvic responses to stressors in female CRF-overexpressing mice

Acute stress affects gut functions through the activation of corticotropin-releasing factor (CRF) receptors. The impact of acute stress on pelvic viscera in the context of chronic stress is not well characterized. We investigated the colonic, urinary, and locomotor responses monitored as fecal pellet output (FPO), urine voiding, and ambulatory activity, respectively, in female and male CRF-overexpressing (CRF-OE) mice, a chronic stress model, and their wild-type littermates (WTL). Female CRF-OE mice, compared with WTL, had enhanced FPO to 2-min handling (150%) and 60-min novel environment (155%) but displayed a similar response to a 60-min partial restraint stress. Female CRF-OE mice, compared with WTL, also had a significantly increased number of urine spots (7.3 +/- 1.4 vs. 1.3 +/- 0.8 spots/h) and lower locomotor activity (246.8 +/- 47.8 vs. 388.2 +/- 31.9 entries/h) to a novel environment. Male CRF-OE mice and WTL both responded to a novel environment but failed to show differences between them in colonic and locomotor responses. Male WTL, compared with female WTL, had higher FPO (113%). In female CRF-OE mice, the CRF(1)/CRF(2) receptor antagonist astressin B and the selective CRF(2) receptor agonist mouse urocortin 2 (injected peripherally) prevented the enhanced defecation without affecting urine or locomotor responses to novel environment. RT-PCR showed that CRF(1) and CRF(2) receptors are expressed in the mouse colonic tissues. The data show that chronic stress, due to continuous central CRF overdrive, renders female CRF-OE mice to have enhanced pelvic and altered behavioral responses to superimposed mild stressors and that CRF(1)-initiated colonic response is counteracted by selective activation of CRF(2) receptor.     

根田鼠粪便皮质酮的检测效能

为验证根田鼠粪便皮质酮的可检测效能,本研究检测根田鼠粪便皮质酮含量的昼夜变化,并检测急性应激后和慢性应激期间根田鼠粪便皮质酮含量变化,及其慢性应激个体的HPA 轴负反馈功能。结果表明,根田鼠粪便皮质酮水平具有明显的似昼夜节律,粪便中皮质酮含量的最高点出现在08:00 和24:00,最低点在12:00 和16:00;在终止急性应激12 h 后,根田鼠粪便皮质酮含量显著增加,且有性别间差异;慢性应激根田鼠粪便皮质酮含量始终保持在高水平;再次急性应激,慢性应激根田鼠个体的粪便皮质酮含量较对照个体升高的时间延后。上述结果说明,根田鼠的粪便皮质酮含量能够反映机体所处的生理状态及应激水平,因此,该方法可用于野外根田鼠种群的相关研究并具有可靠性。     

成年小鼠血液系统对亚磁场的响应

目的:研究亚磁场对成年小鼠血液系统的影响。方法:将成年雄性C57BL/6小鼠(4-6周,20±2g,n20,每笼4只)随机分组,分别饲养在模拟亚磁场环境(500nT)和对照地磁场环境(~50μT)。每周定时监测动物体重变化和饮食消耗两次。一个月后,采集亚磁处理小鼠和地磁对照小鼠全血和血清样品,分别进行血常规监测和血清微量元素分析。同时检测血清中过氧化氢(H2O2)的含量,以及超氧化物歧酶(SOD)和过氧化氢酶(CAT)的活力。结果:亚磁场处理过程中,动物体重和饮食消耗与地磁对照没有显著差异,但是体重增量在2周后(14天-24天)比对照组有显著降低(P0.05)。一个月亚磁场处理后,红细胞,血小板和总白细胞处于正常水平,没有发生显著变化,但是中性粒细胞水平显著上升(P0.05)。血清中微量元素水平和氧化应激指标没有显著变化。结论:成年小鼠在亚磁场中经历了一定程度的适应反应。经过一个月连续亚磁场处理,血液系统能够维持健康水平,但是嗜中性粒细胞对亚磁场存在明显响应。     

Mice with the testicular feminization mutation demonstrate a role for androgen receptors in the regulation of anxiety-related behaviors and the hypothalamic–pituitary–adrenal axis

Testosterone (T) appears to play a role in anxiety and sensorimotor gating in rodents, but whether T acts through the androgen receptor (AR) to influence these behaviors is less clear. We compared adult genetic male mice with the testicular feminization mutation (Tfm), which lack functional ARs, to wild type male littermates (wt males) on an assay of sensorimotor gating (prepulse inhibition of the acoustic startle response; PPI) and several tests thought to reflect anxiety: open field exposure, novel object exposure, elevated plus maze (EPM), and light/dark (LD) box. PPI was similar between groups, but indices of anxiety in the novel object and LD box tests were increased in Tfm males with no significant differences found in the open field or EPM. Since Tfm male mice have decreased circulating T, the same tests were conducted in mice that were gonadectomized (wt males) or sham-operated (Tfm males) as adults and supplemented with T or nothing (B). While T treatment reduced indices of anxiety in the novel object and LD box tests in wt males, it was ineffective in Tfm males. Increased indices of anxiety in Tfm males appear to be related to hyper-activation of the hypothalamic–pituitary–adrenal axis since levels of the stress hormone corticosterone were elevated in Tfm males compared to wt males at baseline and at several time points after exposure to a novel object. These findings demonstrate that ARs influence anxiety and stress responses in mice.     

Loss of hippocampal neuronal nitric oxide synthase contributes to the stress-related deficit in learning and memory

Nitric oxide (NO) has been involved in many pathophysiological brain processes. However, the exact role of NO in the cognitive deficit associated to chronic stress exposure has not been elucidated. In this study, we investigated the participation of hippocampal NO production and their regulation by protein kinase C (PKC) in the memory impairment induced in mice subjected to chronic mild stress model (CMS). CMS mice showed a poor learning performance in both open field and passive avoidance inhibitory task respect to control mice. Histological studies showed a morphological alteration in the hippocampus of CMS mice. On the other hand, chronic stress induced a diminished NO production by neuronal nitric oxide synthase (nNOS) correlated with an increment in gamma and zeta PKC isoenzymes. Partial restoration of nNOS activity was obtained after PKC activity blockade. NO production by inducible nitric oxide synthase isoform was not detected. The magnitude of oxidative stress, evaluated by reactive oxygen species production, after excitotoxic levels of NMDA was increased in hippocampus of CMS mice. Moreover, ROS formation was higher in the presence of nNOS inhibitor in both control and CMS mice. Finally, treatment of mice with nNOS inhibitors results in behavioural alterations similar to those observed in CMS animals. These findings suggest a novel role for nNOS showing protective activity against insults that trigger tissue toxicity leading to memory impairments.     

Chronic exposure to an extremely low‐frequency magnetic field induces depression‐like behavior and corticosterone secretion without enhancement of the hypothalamic–pituitary–adrenal axis in mice

An extremely low‐frequency magnetic field (ELF‐MF) is generated by power lines and household electrical devices. Many studies have suggested an association between chronic ELF‐MF exposure and anxiety and/or depression. The mechanism of these effects is assumed to be a stress response induced by ELF‐MF exposure. However, this mechanism remains controversial. In the present study, we investigated whether chronic ELF‐MF exposure (intensity, 3 mT; total exposure, 200 h) affected emotional behavior and corticosterone synthesis in mice. ELF‐MF‐treated mice showed a significant increase in total immobility time in a forced swim test and showed latency to enter the light box in a light–dark transition test, compared with sham‐treated (control) mice. Corticosterone secretion was significantly high in the ELF‐MF‐exposed mice; however, no changes were observed in the amount of the adrenocorticotropic hormone and the expression of genes related to stress response. Quantification of the mRNA levels of adrenal corticosteroid synthesis enzymes revealed a significant reduction in Cyp17a1 mRNA in the ELF‐MF‐exposed mice. Our findings suggest the possibility that high intensity and chronic exposure to ELF‐MF induces an increase in corticosterone secretion, along with depression‐ and/or anxiety‐like behavior, without enhancement of the hypothalamic–pituitary–adrenal axis. Bioelectromagnetics 34:43–51, 2013. © 2012 Wiley Periodicals, Inc.     

Mice with the testicular feminization mutation demonstrate a role for androgen receptors in the regulation of anxiety-related behaviors and the hypothalamic-pituitary-adrenal axis

Testosterone (T) appears to play a role in anxiety and sensorimotor gating in rodents, but whether T acts through the androgen receptor (AR) to influence these behaviors is less clear. We compared adult genetic male mice with the testicular feminization mutation (Tfm), which lack functional ARs, to wild type male littermates (wt males) on an assay of sensorimotor gating (prepulse inhibition of the acoustic startle response; PPI) and several tests thought to reflect anxiety: open field exposure, novel object exposure, elevated plus maze (EPM), and light/dark (LD) box. PPI was similar between groups, but indices of anxiety in the novel object and LD box tests were increased in Tfm males with no significant differences found in the open field or EPM. Since Tfm male mice have decreased circulating T, the same tests were conducted in mice that were gonadectomized (wt males) or sham-operated (Tfm males) as adults and supplemented with T or nothing (B). While T treatment reduced indices of anxiety in the novel object and LD box tests in wt males, it was ineffective in Tfm males. Increased indices of anxiety in Tfm males appear to be related to hyper-activation of the hypothalamic–pituitary–adrenal axis since levels of the stress hormone corticosterone were elevated in Tfm males compared to wt males at baseline and at several time points after exposure to a novel object. These findings demonstrate that ARs influence anxiety and stress responses in mice.     

Ape conservation physiology: fecal glucocorticoid responses in wild Pongo pygmaeus morio following human visitation

Nature-based tourism can generate important revenue to support conservation of biodiversity. However, constant exposure to tourists and subsequent chronic activation of stress responses can produce pathological effects, including impaired cognition, growth, reproduction, and immunity in the same animals we are interested in protecting. Utilizing fecal samples (N = 53) from 2 wild habituated orangutans (Pongo pygmaeus morio) (in addition to 26 fecal samples from 4 wild unhabituated orangutans) in the Lower Kinabatangan Wildlife Sanctuary of Sabah, Malaysian Borneo, we predicted that i) fecal glucocorticoid metabolite concentrations would be elevated on the day after tourist visitation (indicative of normal stress response to exposure to tourists on the previous day) compared to samples taken before or during tourist visitation in wild, habituated orangutans, and ii) that samples collected from habituated animals would have lower fecal glucocorticoid metabolites than unhabituated animals not used for tourism. Among the habituated animals used for tourism, fecal glucocorticoid metabolite levels were significantly elevated in samples collected the day after tourist visitation (indicative of elevated cortisol production on the previous day during tourist visitation). Fecal glucocorticoid metabolite levels were also lower in the habituated animals compared to their age-matched unhabituated counterparts. We conclude that the habituated animals used for this singular ecotourism project are not chronically stressed, unlike other species/populations with documented permanent alterations in stress responses. Animal temperament, species, the presence of coping/escape mechanisms, social confounders, and variation in amount of tourism may explain differences among previous experiments. Acute alterations in glucocorticoid measures in wildlife exposed to tourism must be interpreted conservatively. While permanently altered stress responses can be detrimental, preliminary results in these wild habituated orangutans suggest that low levels of predictable disturbance can likely result in low physiological impact on these animals.     

Low-ranking individuals present high and unstable fecal cortisol levels in provisioned free-ranging adult male rhesus macaques (<Emphasis Type="Italic">Macaca mulatta</Emphasis>) during the birth season in a mountain area of northern China

Social hierarchy commonly exists in animal societies, affecting both the endocrine functioning and the behavior of animals. In nonhuman primates, the relationship between social rank and cortisol levels varies across species and even within species. Here, we assessed the relationships between social rank and fecal cortisol levels in adult male Taihangshan macaques (rhesus macaques, Macaca mulatta tcheliensis) from the provisioned, free-ranging Wulongkou-2 (WLK-2) group inhabiting Wulongkou Scenic Area, Jiyuan, China. From March to May 2014, we recorded 195 agonistic behaviors and collected 54 fresh fecal samples from eight adult male Taihangshan macaques. Males were assigned a social rank according to an agonistic behavior matrix, and enzyme-linked immunosorbent assay was then used to measure the cortisol concentration in the fecal samples. We found that social rank among the eight male Taihangshan macaques in WLK-2 group followed a strict linear hierarchy, and that fecal cortisol levels were significantly higher and more variable in low-ranking males than in more dominant individuals. Age was not significantly associated with social rank or fecal cortisol levels. Our results suggest that social rank and maintenance of the social hierarchy within the WLK-2 group is a chronic stressor, with low-ranking males maintaining heightened stress levels and enlarged reactive scope relative to dominant males. This provides new support for the theory that social environment can influence endocrine functioning.     

Corticosteroid,catecholamine and glucose plasma levels in rabbits after repeated exposure to a novel environment or administration of (1–24)ACTH or insulin

The responsiveness of the adrenal cortex and the sympathoadrenal-medullary system to stress factors and administration of (1–24) ACTH and insulin was studied in adult rabbits. In comparison to untreated animals, exposure to a novel environment for 10 min followed by artery puncture on 6 consecutive days elicited a moderate increase of corticosteroid (C), norepinephrine (NE) and epinephrine (E) plasma levels. Intramuscular injection of 50 μg/kg body weight (1–24) ACTH increased C, NE and E plasma levels. Saline injection resulted in elevated NE levels; C, E and glucose remained unchanged. After injection of 1.0 IU/kg body weight insulin C levels were higher than those found after exposure to a novel environment for 10mmin followed by artery puncture; similarly, NE and E were increased.In accordance with results obtained in the rat or mouse the sympathoadrenal-medullary system in the rabbit is stimulated by stress factors such as handling, artery puncture or injection of (1–24) ACTH or insulin. In contrast the adrenal cortex can be stimulated only to a certain extent by these manipulations. An increased activation of adrenal cortex cells occurs only after insulin, a maximum stimulation only after (1–24) ACTH administration.     

When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confound a multiregional assessment

Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed‐exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco‐region or when postdeposition exposure can be minimized.     

Effects of aversive experience on the behavior within a custom-made plus maze in the short-tailed fruit bat, Carollia perspicillata

Stress exposure evokes a variety of physiological and behavioral responses in an organism, enabling it to cope with stressful situations and changes in the environment. In a previous study, we found that subjecting individuals of Carollia perspicillata to a chronic immobilization stress paradigm resulted in a significant increase of fecal cortisol concentrations. In the present study, we investigated the influence of stress on the behavior of C. perspicillata, by adapting a commonly used behavioral paradigm for characterizing coping styles of animals (i.e., the elevated-plus maze) to bats. Adult bats were subjected 1?h/day to immobilization over a period of 10?days. On the subsequent day, the behavior of each animal was analyzed in a custom-made plus maze, consisting of four arms (two open and two enclosed ones) and designed 3D because of the bats' ability to fly. In this newly invented design, we compared the behaviors of stressed animals and controls. Changes in locomotor and exploratory behavior suggest two divergent adaptive behaviors in C. perspicillata following the chronic stress paradigm, possibly indicating different stress coping styles.     

Estrogen influences the effect of immobilization stress on immunoreactive beta-endorphin levels in the female rat pituitary

Immunoreactive beta-endorphin (IR-BE) levels in the plasma, anterior pituitary (AP), the neurointermediate lobe of the pituitary (NIL), and the hypothalamus were determined in castrated female rats and castrated female rats treated with estradiol benzoate (estrogen), after exposure to acute (once for 45 min) or chronic (45 min each day for 15 consecutive days) immobilization stress. Acute and chronic stress increased plasma levels of IR-BE to the same extent in castrated female rats and castrated female rats treated with estrogen. In castrated female rats, acute stress produced an increase in the concentration of IR-BE in the AP, which was attenuated by the administration of estrogen. Although IR-BE in the NIL was not influenced by acute stress in castrated animals, exposure to acute stress resulted in an elevation in IR-BE levels in the NIL of rats given estrogen. Chronic stress did not affect the concentration of IR-BE in the AP of castrated females or castrated females treated with estrogen. Chronic stress did, however, increase the concentration of IR-BE in the NIL of castrated animals. This affect of stress on IR-BE levels in the NIL was potentiated by estrogen administration. IR-BE levels in the hypothalamus were reduced by estrogen and were not affected by acute or chronic stress, regardless of the gonadal steroid environment. As determined by column chromatography, administration of estrogen, as well as subjection to chronic stress, promoted the processing of the proopiomelanocortin precursor to form beta-lipotropin rather than beta-endorphin in the AP. By these methods, the only immunoreactivity detected in the NIL and the hypothalamus was beta-endorphin. These data indicate that IR-BE levels in the plasma, the AP, and the NIL of female rats are affected by immobilization stress and that estrogen modulates the effects of acute immobilization stress on IR-BE levels in the AP and the NIL and the effects of chronic immobilization stress on the levels of IR-BE in the NIL.     

Altered behavioural adaptation in mice with neural corticotrophin-releasing factor overexpression

Overproduction of corticotrophin-releasing factor (CRF), the major mediator of the stress response, has been linked to anxiety, depression and addiction. CRF excess results in increased arousal, anxiety and altered cognition in rodents. The ability to adapt to a potentially threatening stimulus is crucial for survival, and impaired adaptation may underlie stress-related psychiatric disorders. Therefore, we examined the effects of chronic transgenic neural CRF overproduction on behavioural adaptation to repeated exposure to a non-home cage environment. We report that CRF transgenic mice show impaired adaptation in locomotor response to the novel open field. In contrast to wild-type (WT) mice, anxiety-related behaviour of CRF transgenic mice does not change during repeated exposure to the same environment over the period of 7 days or at retest 1 week later. We found that locomotor response to novelty correlates significantly with total locomotor activity and activity in the centre at the last day of testing and at retest in WT but not in CRF transgenic mice. Mice were divided into low responders and high responders on the basis of their initial locomotor response to novelty. We found that differences in habituation and re-exposure response are related to individual differences in locomotor response to novelty. In summary, these results show that CRF transgenic mice are fundamentally different from WT in their ability to adapt to an environmental stressor. This may be related to individual differences in stress reactivity. These findings have implications for our understanding of the role of CRF overproduction in behavioural maladaptation and stress-related psychiatric disorders.     

Escitalopram or Novel Herbal Mixture Treatments during or following Exposure to Stress Reduce Anxiety-Like Behavior through Corticosterone and BDNF Modifications

Anxiety disorders are a major public health concern worldwide. Studies indicate that repeated exposure to adverse experiences early in life can lead to anxiety disorders in adulthood. Current treatments for anxiety disorders are characterized by a low success rate and are associated with a wide variety of side effects. The aim of the present study was to evaluate the anxiolytic effects of a novel herbal treatment, in comparison to treatment with the selective serotonin reuptake inhibitor escitalopram. We recently demonstrated the anxiolytic effects of these treatments in BALB mice previously exposed to one week of stress. In the present study, ICR mice were exposed to post natal maternal separation and to 4 weeks of unpredictable chronic mild stress in adolescence, and treated during or following exposure to stress with the novel herbal treatment or with escitalopram. Anxiety-like behavior was evaluated in the elevated plus maze. Blood corticosterone levels were evaluated using radioimmunoassay. Brain derived neurotrophic factor levels in the hippocampus were evaluated using enzyme-linked immunosorbent assay. We found that (1) exposure to stress in childhood and adolescence increased anxiety-like behavior in adulthood; (2) the herbal treatment reduced anxiety-like behavior, both when treated during or following exposure to stress; (3) blood corticosterone levels were reduced following treatment with the herbal treatment or escitalopram, when treated during or following exposure to stress; (4) brain derived neurotrophic factor levels in the hippocampus of mice treated with the herbal treatment or escitalopram were increased, when treated either during or following exposure to stress. This study expands our previous findings and further points to the proposed herbal compound''s potential to be highly efficacious in treating anxiety disorders in humans.     

Differential effects of cannabinoid exposure and stress on plasma prolactin, growth hormone and corticosterone levels in male mice

Plasma prolactin (PRL) levels were reduced in stressed and non-stressed male mice after a single dose of Δ⁹-tetrahydrocannabinol (THC), the main psychoactive constituent of marihuana, while growth hormone (GH) levers were reduced only in non-stressed animals. Chronic treatment with THC did not affect PRL or GH levels under either condition. Neither acute nor repeated exposure to THC affected plasma corticosterone levels.In contrast to the affects of THC, acute exposure to cannabinol (CBN), a non-psychoactive ingredient in marihuana, increased plasma GH levels in non-stressed mice, while repeated CBN treatments reduced GH levels in stressed animals. Moreover, chronic CBN exposure resulted in decreased peripheral levels of corticosterone in both stressed and non-stressed mice, and reduced plasma PRL levels in stressed mice.Psychoactive and non-psychoactive components of marihuana can exert different effects on endocrine function and on responsivity to stress in male mice.     

Long-term behavioral and neuroendocrine alterations following chronic social stress in mice: implications for stress-related disorders

The period of adolescence is characterized by a high vulnerability to stress and trauma, which might result in long-lasting consequences and an increased risk to develop psychiatric disorders. Using a recently developed mouse model for chronic social stress during adolescence, we studied persistent neuroendocrine and behavioral effects of chronic social stress obtained 12 months after cessation of the stressor. As a reference, we investigated immediate effects of chronic stress exposure obtained at the end of the chronic stress period. Immediately after the 7 week chronic stress period stressed animals show significantly increased adrenal weights, decreased thymus weight, increased basal corticosterone secretion and a flattened circadian rhythm. Furthermore, stressed animals display an increased anxiety-like behavior in the elevated plus maze and the novelty-induced suppression of feeding test. Hippocampal mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) mRNA levels were significantly decreased. To investigate persistent consequences of this early stressful experience, the same parameters were assessed in aged mice 12 months after the cessation of the stressor. Interestingly, we still found differences between formerly stressed and control mice in important stress-related parameters. MR expression levels were significantly lower in stressed animals, suggesting lasting, possibly epigenetic alterations in gene expression regulation. Furthermore, we observed long-term behavioral alterations in animals stressed during adolescence. Thus, we could demonstrate that chronic stress exposure during a crucial developmental time period results in long-term, persistent effects on physiological and behavioral parameters throughout life, which may contribute to an enhanced vulnerability to stress-induced diseases.     

Analyzing corticosterone metabolites in fecal samples of mice: a noninvasive technique to monitor stress hormones

In small animals like mice, the monitoring of endocrine functions over time is constrained seriously by the adverse effects of blood sampling. Therefore, noninvasive techniques to monitor, for example, stress hormones in these animals are highly demanded in laboratory as well as in field research. The aim of our study was to evaluate the biological relevance of a recently developed technique to monitor stress hormone metabolites in fecal samples of laboratory mice. In total, six experiments were performed using six male and six female mice each. Two adrenocorticotropic hormone (ACTH) challenge tests, two dexamethasone (Dex) suppression tests and two control experiments [investigating effects of the injection procedure itself and the diurnal variation (DV) of glucocorticoids (GCs), respectively] were conducted. The experiments clearly demonstrated that pharmacological stimulation and suppression of adrenocortical activity was reflected accurately by means of corticosterone metabolite (CM) measurements in the feces of males and females. Furthermore, the technique proved sensitive enough to detect dosage-dependent effects of the ACTH/Dex treatment and facilitated to reveal profound effects of the injection procedure itself. Even the naturally occurring DV of GCs could be monitored reliably. Thus, our results confirm that measurement of fecal CM with the recently established 5alpha-pregnane-3beta,11beta,21-triol-20-one enzyme immunoassay is a very powerful tool to monitor adrenocortical activity in laboratory mice. Since mice represent the vast majority of all rodents used for research worldwide and the number of transgenic and knockout mice utilized as animal models is still increasing, this noninvasive technique can open new perspectives in biomedical and behavioral science.     

Lake pigments facilitate analysis of fecal cortisol and behavior in group-housed macaques

Fecal steroid analyses are becoming more popular among both field and laboratory scientists. The benefits associated with sampling procedures that do not require restraint, anesthesia, and blood collection include less risk to both subject and investigator, as well as the potential to obtain endocrine profiles that do not reflect the influence of stress. However, the utility of the fecal steroid method has been limited in field conditions because of problems associated with sample identification. Here, we present evidence that Lake pigments are a valuable tool for the identification of individual fecal samples from group-housed female cynomolgus macaques. Further, we present data that suggest that excreted cortisol can be assayed from such samples, leading to the finding that time of day of sample collection influences cortisol concentrations, with morning samples producing higher values (t = 2.769, P = 0.024). Finally, the collection of physiological data from group-housed animals permits the evaluation of the relationship between endocrine status and behavior. This study demonstrated that morning fecal cortisol was significantly correlated with competitive and proximity behaviors, although not with rank in two stable social groups. In conclusion, the utility and validity of fecal steroid analyses continue to expand with further investigations.