Our results did not indicate a relationship between dropping mass and corticosterone metabolite concentrations, which suggests that our findings were linked to the regulation of corticosterone in response to predictable and unpredictable challenges.Ĭitation: Fletcher K, Xiong Y, Fletcher E, Gustafsson L (2018) Glucocorticoid response to both predictable and unpredictable challenges detected as corticosterone metabolites in collared flycatcher droppings.
Also, females appear to downregulate corticosterone during incubation in response to lower ambient temperature and poorer body condition. Our results indicate that the upregulation of corticosterone between incubation and nestling feeding in female birds is crucial for successful reproduction in this species. We also tested how corticosterone metabolite concentrations were affected by ambient temperature and related to body condition in adult birds. In the present study, we aimed to detect changes in levels of corticosterone, the primary bird glucocorticoid, in relation to the phase of reproduction, in a breeding population of collared flycatchers by sampling corticosterone metabolites in droppings. Although the concentration of glucocorticoid metabolites are influenced by faecal mass thereby potentially affecting any differences in hormone metabolites detected amongst samples. An alternative method of quantifying glucocorticoids is as hormone metabolites in faeces or urine giving a historical sample related to the gut passage time and urinary tract that is less sensitive to stressful events which cause spikes in the circulating hormone level. Particularly when quantifying circulating levels of glucocorticoids in the blood which fluctuate rapidly in response to stress. In addition, glucocorticoids are a major part of the stress response and stress induced elevations of the hormone can make it difficult to assess glucocorticoid secretion in response to changes in life-stage and current environmental conditions in wild animals. They also suggest that patients experiencing extended periods of glucocorticoid treatment might benefit from attempts to increase their physical activity as an adjuvant.In most vertebrate animals, glucocorticoid hormones are the chief mediators of homeostasis in response to ecological conditions and as they progress through their lifecycle. These results have significant implications for understanding both the evolution of baseline corticosterone levels and stress-related effects on activity levels. Overall, the responses of both HR and C mice to corticosterone supplementation were “negative” from a health perspective. At the suborganismal level, corticosterone treatment decreased relative adrenal, liver, and triceps surae muscle mass, as well as tail length, but increased both subdermal and reproductive fat pad masses, as well as hematocrit.
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For both HR and C mice, corticosterone treatment strongly suppressed endogenous circulating corticosterone levels, decreased growth rate and adult body mass, increased food and water consumption (both adjusted for body mass), increased entries into closed arms of an elevated plus maze, decreased home-cage activity (total and average intensity), decreased wheel-running distance and maximum speed, and decreased VO 2max. As compared with mice from C lines, HR mice had higher endogenous corticosterone levels higher daily wheel-running distance, duration, and speed higher maximal oxygen consumption during forced exercise (VO 2max) spent more time in the closed arms of an elevated plus maze and had larger reproductive fat pads. We administered 50 μg/mL corticosterone-21-hemisuccinate in the drinking water of both HR and C male mice from weaning through ~8 weeks of age. As compared with four non-selected control (C) lines, mice from the four replicate High Runner (HR) lines have ~2-fold higher baseline circulating corticosterone concentrations as well as ~3-fold higher voluntary wheel running on a daily basis, higher home-cage activity when deprived of wheels, higher maximal aerobic capacity, and smaller body size potentially, all of these differences could be modulated by circulating corticosterone.
To examine further the role of corticosterone in locomotor behavior and associated traits, we utilized laboratory house mice from a long-term experiment that selectively breeds for high levels of voluntary exercise. Changes in circulating corticosterone concentrations can also impact multiple aspects of locomotor behavior, including both motivation and physical ability for exercise. Glucocorticoids, a class of metabolic hormones, impact a wide range of traits (e.g., behavior, skeletal growth, muscle maintenance, glucose metabolism), and variation in concentrations of circulating glucocorticoids (such as corticosterone), at the level of natural individual variation, in relation to endocrine disorders, or from exogenous supplementation, have manifold effects.
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