The effect of chronic psychological stress on corticosterone, plasma metabolites, and immune responsiveness in European starlings
ABSTRACT Although increases in glucocorticoid concentrations during acute stress are believed to help animals survive stressful events, chronic changes in glucocorticoid concentrations can alter metabolism and lead to disease. We studied the effect of chronic psychological stress on corticosterone (CORT), corticosterone binding globulin (CBG), glucose, and triglyceride concentrations as well as immune responsiveness to a T-cell mitogen challenge in European starlings, Sturnus vulgaris. To induce chronic stress we used a chronic stress protocol consisting of five stressors (loud radio, cage tapping, cage rolling, human voice, and bag restraint) administered in random order for 30 min for 4 times/day over 18 days. Total CORT decreased throughout the chronic stress period, which parallels a previous study with starlings. CBG capacity did not significantly change with chronic stress, thus free CORT followed the same pattern of attenuation as total CORT during chronic stress. Despite the change in regulation of CORT release, daytime glucose and triglyceride concentrations did not change with chronic stress. In addition, immune responsiveness in chronically stressed and unstressed birds was similar. Our results, together with a previous study using a similar CSP in European starlings, suggest that starlings physiologically dampen the HPA axis during chronic psychological stress to avoid pathology associated with chronically augmented CORT concentrations such as hyperglycemia and impaired immune function.
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- "Non-declining long-tailed finches and less vulnerable populations of star and black-throated finches did not show dramatically higher CORT levels and lower muscle during moult, suggesting that these populations are likely to be better able to adapt to possible changes in food availability and are less likely to require future conservation management compared with vulnerable populations. This assumes that the decreased stress response of supposed non-vulnerable populations during moult shows that these birds were less stressed during this period, but an alternative explanation would suggest that they were suppressing the stress response due to chronic or longterm stressors, which have been shown to downregulate the release of stress hormones in several species (Romero and Wikelski, 2002; Partecke et al., 2006; Cyr et al., 2007). However, we propose that it is more likely that non-vulnerable populations were simply less stressed, because their body condition profile matched that of birds in good condition (higher muscle and lower fat scores; discussed further below) and did not show evidence of poor condition. "
ABSTRACT: Conservation agencies are often faced with the difficult task of prioritizing what recovery actions receive support. With the number of species under threat of decline growing globally, research that informs conservation priorities is greatly needed. The relative vulnerability of cryptic or nomadic species is often uncertain, because populations are difficult to monitor and local populations often seem stable in the short term. This uncertainty can lead to inaction when populations are in need of protection. We tested the feasibility of using differences in condition indices as an indication of population vulnerability to decline for related threatened Australian finch sub-species. The Gouldian finch represents a relatively well-studied endangered species, which has a seasonal and site-specific pattern of condition index variation that differs from the closely related non-declining long-tailed finch. We used Gouldian and long-tailed finch condition variation as a model to compare with lesser studied, threatened star and black-throated finches. We compared body condition (fat and muscle scores), haematocrit and stress levels (corticosterone) among populations, seasons and years to determine whether lesser studied finch populations matched the model of an endangered species or a non-declining species. While vulnerable finch populations often had lower muscle and higher fat and corticosterone concentrations during moult (seasonal pattern similar to Gouldian finches), haematocrit values did not differ among populations in a predictable way. Star and black-throated finch populations, which were predicted to be vulnerable to decline, showed evidence of poor condition during moult, supporting their status as vulnerable. Our findings highlight how measures of condition can provide insight into the relative vulnerability of animal and plant populations to decline and will allow the prioritization of efforts towards the populations most likely to be in jeopardy of extinction.Conservation Physiology 06/2015; 3(1-1):cov025. DOI:10.1093/conphys/cov025
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- "A possible explanation for such a result could be stress-induced downregulation of corticosterone production due to a negative feedback mechanism (reviewed by ). For instance, chronic psychological stress , feather clipping  and corticosterone administration  have been shown to suppress baseline and/or stress-induced corticosterone levels in birds. Such down-regulation of the endogenous stress response can be relatively long-lasting; for example, up to 20 days in kestrel Falco tinnunculus nestlings . "
ABSTRACT: Assessment of costs accompanying activation of immune system and related neuroendocrine pathways is essential for understanding the selective forces operating on these systems. Here we attempted to detect such costs in terms of disruption to redox balance and interference between different immune system components in captive wild-caught greenfinches (Carduelis chloris). Study birds were subjected to an endotoxin-induced inflammatory challenge and temporary exposure to a psychological stressor (an image of a predator) in a 2*2 factorial experiment. Injection of bacterial endotoxin resulted in up-regulation of two markers of antioxidant protection - erythrocyte glutathione, and plasma oxygen radical absorbance (OXY). These findings suggest that inflammatory responses alter redox homeostasis. However, no effect on markers of oxidative damage to proteins or DNA in erythrocytes could be detected. We found no evidence that the endotoxin injection interfered with antibody production against Brucella abortus antigen or the intensity of chronic coccidiosis. The hypothesis of within-immune system trade-offs as a cost of immunity was thus not supported in our model system. We showed for the first time that administration of endotoxin can reduce the level of corticosterone deposited into feathers. This finding suggests a down-regulation of the corticosterone secretion cascade due to an endotoxin-induced immune response, a phenomenon that has not been reported previously. Exposure to the predator image did not affect any of the measured physiological parameters.PLoS ONE 06/2013; 8(6):e67545. DOI:10.1371/journal.pone.0067545 · 3.23 Impact Factor
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- "Spontaneous activity evaluated at the end of the chronic stress procedure differed significantly between treated and control quail, but not between genetic lines. Dalm et al.  pointed out a lack of studies concerning the detailed pattern of activity of rodent models of chronic stress in their home cage, and none of the few studies on bird’s chronic psychological stress evaluated behaviour in their home cage , , , –, . Our present study evidences that treated quail rested less than did control quail. "
ABSTRACT: Chronic stress is known to enhance mammals' emotional reactivity and alters several of their cognitive functions, especially spatial learning. Few studies have investigated such effects in birds. We investigated the impact of a two-week stress on Japanese quail's emotional reactivity and spatial learning. Quail is an avian model widely used in laboratory studies and for extrapolation of data to other poultry species. As sensitivity to chronic stress can be modulated by intrinsic factors, we tested juvenile female Japanese quail from three lines, two of them divergently selected on tonic immobility duration, an indicator of general fearfulness. The different emotional reactivity levels of quail belonging to these lines can be revealed by a large variety of tests. Half of the birds were submitted to repeated unpredictable aversive events for two weeks, whereas the other half were left undisturbed. After this procedure, two tests (open field and emergence tests) evaluated the emotional reactivity of treated and control quails. They were then trained in a T-maze for seven days and their spatial learning was tested. The chronic stress protocol had an impact on resting, preening and foraging in the home cage. As predicted, the emotional reactivity of treated quails, especially those selected for long tonic immobility duration, was higher. Our spatial learning data showed that the treatment enhanced acquisition but not memorization. However, intrinsic fearfulness did not seem to interact with the treatment in this test. According to an inverted U-shaped relationship between stress and cognition, chronic stress can improve the adaptability of birds to a stressful environment. We discussed the mechanisms possibly implied in the increase of emotional reactivity and spatial abilities.PLoS ONE 10/2012; 7(10):e47475. DOI:10.1371/journal.pone.0047475 · 3.23 Impact Factor