Chronic stress alters concentrations of corticosterone receptors in a tissue-specific manner in wild house sparrows (Passer domesticus) (original) (raw)
Related papers
Journal of Neuroendocrinology, 2009
The acute stress response is an adaptive physiological mechanism that allows animals to respond to and survive noxious stimuli in the environment. When chronic stress occurs, these same adaptive mechanisms no longer aid in survival but, instead, negatively impact on the general health of the animal (1). Chronic stress disrupts many systems throughout the body, including the hypothalamic-pituitary-adrenal (HPA) axis, which orchestrates the vertebrate stress response. As in the mammalian system, the avian HPA axis is a neuroendocrine pathway that stimulates the release of corticotrophin-releasing factor (CRF) and the avian homologue of vasopressin, vasotocin (AVT). Both these hormones stimulate the pituitary gland to secrete adrenocorticotrophin hormone (ACTH) from the corticotrophs, which then circulates in the plasma to cause glucocorticoid release from the adrenal cortex. The main glucocorticoid released in birds in response to stress is corticosterone (2, 3). Chronic stress affects the HPA by altering the sensitivity to the secretory hormones along the axis, as well as disrupting the glucocorticoid negative-feedback system (4, 5). Prior studies performed by our research group demonstrate that wild-caught European starlings (Sturnus vulgaris) exposed to chronic stress have reduced pituitary sensitivity to AVT, altered adrenal responsiveness to ACTH, and decreased secretion of AVT and ACTH, which together lead to a lower baseline and acute-stress-induced glucocorticoid (i.e. corticosterone) release (6). Studies on free-living female starlings during incubation exposed to chronic stress showed decreased baseline plasma corticosterone concentrations and reduced reproductive success. In addition, the surviving nestlings born to chronically-stressed mothers demonstrated a sensitised corticosterone response to acute restraint stress . These studies highlight two main points: (1) chronic stress alters the responsiveness of the physiological stress response in wild animals and (2) chronic stress has a negative impact on fitness. However, the underlying mechanisms driving these changes in birds have yet to be determined. ).
2014
Glucocorticoid hormones like corticosterone (CORT) play essential metabolic roles at both baseline and stress-induced concentrations, and CORT titers vary seasonally in patterns occurring across many different vertebrate species. It has been hypothesized that CORT may vary seasonally due to changing energy requirements at different times of year. However, hormone effects are dependent on binding to receptors in target tissues, and receptors might also vary seasonally. CORT alters metabolism primarily through binding to two receptors, the high-affinity mineralocorticoid receptor (MR) and low-affinity glucocorticoid receptor (GR). We quantified GR and MR in metabolic tissues (liver, kidney, omental and subcutaneous fat, and gastrocnemius and pectoralis muscle) of wild-caught house sparrows (Passer domesticus) to assess these tissues' capacity to respond to CORT-mediated metabolic demands. We quantified receptors using radioligand binding assays in early and late winter, pre-egg-laying, breeding, late breeding and molt (n = 12 at each stage). MR binding did not vary significantly in any tissue over the course of the year. Because MR is associated with baseline CORT effects, this suggests that changing hormone titers may primarily regulate baseline CORT effects on metabolism. Seasonal modulation of GR binding occurred in every tissue but omental fat, though peak receptor density did not coincide with peak stress-induced CORT concentrations measured previously. Because GR is associated with stress-induced CORT effects, these data demonstrate seasonal patterns in stress-induced CORT are not driven by metabolic needs alone, although at different times of year sparrows may vary which tissue types respond to increased energy demands resulting from exposure to stressors.
After a migratory flight of several thousand kilometers to their high arctic breeding grounds, red knots (Calidris canutus islandica, Scolopacidae) showed high baseline concentrations of plasma corticosterone (58 ng/mL). Such high baseline corticosterone levels may be conditional for the right behavioral and metabolic adjustments to environmental and social stresses that shorebirds experience on arrival in an unpredictable tundra breeding environment. Despite the high baseline levels of corticosterone, red knots still showed a marked stress response during the postarrival period, with corticosterone concentrations increasing significantly during a 60-min period of confinement. Baseline levels of corticosterone declined as the breeding season progressed. Red knots with brood patches, that is, birds that had completed egg laying and commenced incubation, had a reduced adrenocortical response to the stress of confinement compared with red knots with no, or with halfdeveloped, brood patches. This is consistent with the idea that birds breeding in extreme environments with short breeding seasons may exhibit a decreased adrenocortical response to stressful events to prevent high corticosterone concentrations from inducing interruptions of reproductive behavior.
Endocrinology, 2009
There is growing international interest in how environmental conditions experienced during development can shape adult phenotypes and the extent to which such induced changes are adaptive. One physiological system that links an individual to changes in environmental circumstances during development is the hypothalamic-pituitary-adrenal axis. Mammalian studies have linked early postnatal stress to later changes in the hypothalamic-pituitary-adrenal axis; however, the physiological link [lactational corticosterone (CORT) transfer] between mother and offspring during postnatal development constrains the ability to determine the direct effects of such stressors on subsequent physiology and behavior. Here we present a novel model using an avian species, the zebra finch (Taeniopygia guttata), in which maternal hormonal transfer during postnatal development is likely to be absent. Postnatal exposure of chicks to the stress hormone CORT was manipulated for a 16-d period up until nutritional...
Hormones and Behavior, 2012
In avian plasma, testosterone (T) and corticosterone (CORT) compete to bind with corticosterone-binding globulin (CBG). Elevation of CBG may function to "buffer" the tissues against high circulating levels of T and stress-induced levels of CORT. To demonstrate the effects of acute stress on CBG and T levels and their biological functions, we investigated seasonal changes of baseline and stress-induced T and CBG levels in Eurasian Tree Sparrows (Passer montanus) during different life stages using the capture-handling-restraint stress method. Our results show that (1) male sparrows had significantly higher baseline T levels and CBG capacities during the nest building, the first egg-laying, and the first nestling stages, and significantly decreased stress-induced T levels only during the nest building and the first egg-laying stages. They also expressed significantly increased stress-induced CBG capacities during the second nestling stage. (2) Females showed significantly higher baseline CBG capacities but significantly decreased stress-induced CBG capacities during the nest building stage, and females also showed significantly increased stress-induced CBG capacities during the second egg-laying and the second nestling stages. Therefore, the seasonal fluctuations of baseline CBG in both sexes and baseline T in males reflect their adaptive strategies for optimizing their physiological and behavioral states to the life history cycle. The different patterns of stress-induced CBG in females suggest CBG functions as an essential mediator in regulating stress response to unpredictable perturbations. Our results highlight the need for future studies of stress-induced CBG and T levels on a wide range of vertebrate species that vary in different life history stages to gain a full understanding of the mechanisms that underlie biological functions of CBG and T for unpredictable stressors.
General and Comparative Endocrinology, 2001
The effects of age, handling-induced stress, yolk androgens, and body condition on plasma corticosterone levels were investigated in free-living nestling American kestrels, Falco sparverius, a semialtricial falcon species. In an observational study, corticosterone levels varied with age and handling time. Specifically, corticosterone was low until age 15 days and then rose from age 20 through 25 days. Nestlings as young as age 10 days showed a handling-induced rise in corticosterone. Neither sex nor hatching order of the nestling affected corticosterone levels. Concentrations of maternally derived yolk androgens have previously been shown to be lower in first-laid than in later-laid eggs in the clutch. In an experimental study, androgens were injected into the yolk of the first-laid egg to elevate its levels to those of later-laid eggs, a treatment that substantially reduces nestling body condition compared with that of controls. Yolk androgen treatment elevated posthatching corticosterone levels compared with those of controls, and corticosterone levels were negatively correlated with body condition. These findings indicate that even very young, developing birds can show stress-induced increases in corticosterone and that age-related changes in corticosterone secretion may be modified by body condition and maternal effects such as yolk androgen deposition. The short-and long-term consequences of high glucocortico-steroid levels in young, developing vertebrates are largely unknown.
Corticosterone Responses in Wild Birds: The Importance of Rapid Initial Sampling
The Condor, 2002
Corticosterone concentrations in birds usually rise in response to capture and handling, and it is often assumed that this change is predictable. We tested this assumption by leaving Gambel's White-crowned Sparrows (Zonotrichia leucophrys gambelii), House Sparrows (Passer domesticus), and Lapland Longspurs (Calcarius lapponicus) in nets or traps for 15 min following capture and comparing their corticosterone response over the next 60 min with birds removed immediately. White-crowned Sparrows and House Sparrows left in mist nets for 15 min and then bled had significantly elevated corticosterone concentrations compared to controls that were immediately removed from the net and bled. Corticosterone concentrations over the next 45 min of handling and restraint were similar between groups. In another experiment, White-crowned Sparrows and Lapland Longspurs were captured using seed-baited Potter traps. The corticosterone response of White-crowned Sparrows left in the trap for 15 min did not differ from White-crowned Sparrows removed immediately. Leaving Lapland Longspurs in the trap had no effect in the initial 10 min of handling and restraint, but at 30 and 60 min these birds had significantly lower corticosterone concentrations than longspurs removed immediately from the trap. These data indicate that failing to immediately remove birds from nets or traps can alter the corticosterone response to subsequent stressful stimuli in unpredictable ways. This result emphasizes that the elapsed time from capture is a critical variable in assessing stress responses in free-living birds.
General and comparative endocrinology, 2017
We conducted a review of scientific articles published between 2000 and 2014 and evaluated how frequently various aspects of cortisol and corticosterone (CORT) actions have been considered in studies on wild vertebrates. Results show that (1) the notion that CORT are stress-responsive hormones is central in our theoretical frameworks and it is reflected by the fact that several articles refer to CORT as "stress hormones". (2) The large majority of studies do not contemplate the possibility of decrease and no change in CORT levels in response to chronic stressors. (3) Our ideas about CORT actions on energy balance are slanted towards the mobilization of energy, though there are several studies considering -and empirically addressing- CORT's orexigenic actions, particularly in birds. (4) The roles of CORT in mineral-water balance, though widely documented in the biomedical area, are virtually ignored in the literature about wild vertebrates, with the exception of studies...