Chronic stress alters concentrations of corticosterone receptors in a tissue-specific manner in wild house sparrows (Passer domesticus)

Abstract

The physiological stress response results in release of glucocorticoid hormones such as corticosterone (CORT). Whereas short-term activation of this response helps animals cope with environmental stressors, chronic activation can result in negative effects including metabolic dysregulation and reproductive failure. However, there is no consensus hormonal profile of a chronically stressed animal, suggesting that researchers may need to look beyond hormone titers to interpret the impacts of chronic stress. In this study, we brought wild house sparrows (Passer domesticus) into captivity. We then compared glucocorticoid and mineralocorticoid receptor concentrations in sparrows exposed either to a standardized chronic stress protocol (n=26) or to standard husbandry conditions (controls; n=20). We used radioligand binding assays to quantify receptors in whole brain, liver, kidneys, spleen, gonads, gastrocnemius and pectoralis muscle, omental and subcutaneous fat, and bib and back skin. In most tissues, CORT receptors did not differ between controls and stressed animals, although we found marginal increases in receptor density in kidney and testes in stressed birds at some time points. Only in pectoralis muscle was there a robust effect of chronic stress, with both receptor types higher in stressed animals. Increased pectoralis sensitivity to CORT with chronic stress may be part of the underlying mechanism for muscle wasting in animals administered exogenous CORT. Furthermore, the change in pectoralis was not paralleled by gastrocnemius receptors. This difference may help explain previous reports of a greater effect of CORT on pectoralis than on other muscle types, and indicate that birds use this muscle as a protein reserve. KEY WORDS: Hypothalamic-pituitary-adrenal axis, Glucocorticoids, Peripheral receptors, Bird INTRODUCTIONActivation of the hypothalamus-pituitary-adrenal (HPA) axis results in the release of glucocorticoid hormones (cortisol and/or corticosterone depending on the species, hereafter CORT). At baseline concentrations, CORT helps regulate metabolism, activity levels and feeding behavior; at the higher concentrations caused by a stressor, CORT is an essential component of the vertebrate stress response (Landys et al., 2006;Sapolsky et al., 2000). During the stress response, CORT helps animals mobilize energy stores, enhances certain immune components and promotes escape and selfmaintenance behaviors (Spencer et al., 2001;Wingfield and Kitaysky, 2002). RESEARCH ARTICLEDepartment of Biology, Tufts University, Medford, MA 02155, USA.*Author for correspondence (christine.lattin@tufts.edu) Received 7 February 2014; Accepted 26 April 2014However, sustained high levels of CORT due to frequent or prolonged stressors can result in a number of stress-related pathologies, including suppression of reproduction and the immune system, metabolic dysregulation and cognitive impairment (Dallman et al., 2003; de Kloet et al., 2005;Martin, 2009;Sapolsky et al., 2000). Chronic stress is thought to result once COR...

House sparrows (Passer domesticus) adjusted hypothalamic‐pituitary‐adrenal axis negative feedback and perch hopping activities in response to a single repeated stimulus

“…This lack of change highlights that baseline Cort does not always change in a consistent manner in different species. This experiment was designed so that the initial 4‐day period of the protocol would be interpreted by the birds as potentially noxious and thus trigger physiological changes consistent with chronic stress, such as altered baseline Cort (Cyr et al, ; Fischer et al, ; Lattin & Romero, ; Love, Lovern, & DuRant, ; Rich & Romero, ). However, in this experiment, 4 days appeared to be too short to elicit changes in baseline Cort as birds were likely only on the cusp of experiencing symptoms of chronic stress.…”

“…However, in this experiment, 4 days appeared to be too short to elicit changes in baseline Cort as birds were likely only on the cusp of experiencing symptoms of chronic stress. Another study of house sparrows found that even 21 days of a chronic stress protocol comprised of rotated, randomly presented stimuli, did not elicit significant changes in baseline Cort (Lattin & Romero, ). The authors propose that because house sparrows are such successful invaders and human commensals, they may be less susceptible to these chronic stress protocols.…”

“…The experimental design was based on prior chronic stress studies that indicated that the hormonal effects of chronic stress are typically initiated within 8–12 days (Awerman & Romero, ; Cyr et al, ; DuRant, Arciniega, Bauer, & Romero, ; Gormally, Wright‐Lichter, Reed, & Romero, ; Lattin & Romero, ). In several of these studies, birds were exposed to different stressors at four different unpredictable times throughout the day for up to 3 weeks.…”

Experimental effects of early‐life corticosterone on the hypothalamic–pituitary–adrenal axis and pre‐migratory behaviour in a wild songbird

“…exaggerated stress response: Pravosudov & Kitaysky 2006;Lendvai et al 2009;Spencer et al 2009, Banerjee et al 2012, Schmidt et al 2014attenuated stress response: Rich & Romero 2005;Cyr et al 2007;Kriengwatana et al 2014;Lattin & Romero 2014) and this may depend on how glucocorticoids are experimentally elevated early in life. In addition, the endocrine effect of early life stress may also manifest at different levels of HPA axis function as baseline functions are largely mediated by high affinity mineralocorticoid receptors whereas functions related to increased HPA axis activation (i.e.…”

Lipids in maternal diet influence yolk hormone levels and post‐hatch neophobia in the domestic chick

“…Third, it is known that maternal environmental stress induces similar increases in hens' yolk hormones as we found in the hens fed the n-3 diet Guibert et al, 2010). Glucocorticoid receptors can be modified by stressful conditions in a variety of avian species (Japanese quail, Zimmer & Spencer, 2014;starlings, Dickens, Romero, Cyr, Dunn, & Meddle, 2009; house sparrow, Lattin & Romero, 2014) and play a role in the lipid metabolism of the white-crowned sparrow (Landys, Piersma, Ramenofsky, & Wingfield, 2004) (Landys, Ramenofsky, Guglielmo, & Wingfield, 2004). As in mice, a deficiency of n-3 PUFA can alter corticosterone secretion via modifications in glucocorticoid receptors (GRs) of the prefrontal cortex, but not in the HPA-axis (Larrieu, Hilal, De Smedt-Peyrusse, Sans, & Laye, 2016).…”