Roles and Mechanistic Bases of Glucocorticoid Regulation of Avian Reproduction

Abstract

To maximize fitness, organisms must invest energetic and nutritional resources into developing, activating, and maintaining reproductive physiology and behavior. Corticosterone (CORT), the primary avian glucocorticoid, regulates energetic reserves to meet metabolic demands. At low (baseline) plasma levels, CORT activates avian mineralocorticoid receptors and may stimulate lipid mobilization, foraging activity, and feeding behavior. During stress in birds, elevated plasma CORT also stimulates glucocorticoid receptors and may promote glycemia, lipolysis, and proteolysis. Furthermore, CORT orchestrates physiological and behavioral adjustments to perceived threats. While many avian studies demonstrate effects of CORT on reproduction, few studies have elucidated the mechanisms, including receptor activation and site(s) of action, which underlie these effects. Even fewer studies have investigated how low and elevated plasma CORT regulates energetic reserves to meet the metabolic demands of reproduction. Here, we propose several hypotheses to clarify the direct and indirect effects of CORT on avian reproductive physiology and behavior. In addition, we emphasize the need for new manipulative studies involving alterations of endogenous plasma CORT levels and/or food availability to elucidate how CORT regulates the energetic demands of reproduction.

Proteomic analysis of fertilized egg yolk proteins during embryonic development

“…At 18 ED, ovoinhibitors and ovalbumin were involved in response to mineralocorticoid, corticosterone, glucocorticoid, corticosteroid, and ketone physiological reaction, while glucocorticoid and mineralocorticoid are involved in the control of a variety of physiological processes, including reproduction, metabolism, salt balance, inflammation, and immunity ( Barnes and Adcock, 2003 , Fu and Vallon, 2014 , Deviche et al., 2017 ). Therefore, the high abundance of ovalbumin and ovoinhibitors might have significant physiological implications for the embryo development before hatching.…”

Molecular and Neuroendocrine Approaches to Understanding Trade-offs: Food, Sex, Aggression, Stress, and Longevity—An Introduction to the Symposium

“…Similarly, activation of RFRP-3 cells in the brain is increased by food restriction and this effect is modulated by ovarian steroids ( Schneider et al 2017 ). This theme was echoed in the contributions of Deviche in avian species and Bentley a wide array of chordates and protochordates ( Bentley et al 2017 ; Deviche et al 2017 ). Context is important.…”

“…Adult offspring of lactationally food-restricted dams showed reduced levels of attractivity, proceptivity, and receptivity, which are likely to influence their reproductive success ( Ferkin 2017 ). All of the contributors are working on different physiological systems, including the stress response ( Bentley et al 2017 ), hibernation ( Willis 2017 ), immunity ( Crespi and Travis 2017 ), ingestive behavior ( Brozek et al 2017 ; Crespi and Travis 2017 ; Emmons 2017 ; Ferkin 2017 ; Lucas et al 2017 ; Schneider et al 2017 ), and reproduction ( Brozek et al 2017 ; Crespi and Travis 2017 ; Deviche et al 2017 ; Emmons 2017 ; Ferkin 2017 ; Lucas et al 2017 ; Schneider et al 2017 ). Not all contributors to this symposium are testing specific hypotheses about microevolutionary trade-offs, and many of the contributors are primarily concerned with neuroendocrine mechanisms.…”

Hypothalamic–Pituitary–Thyroid Axis Crosstalk With the Hypothalamic–Pituitary–Gonadal Axis and Metabolic Regulation in the Eurasian Tree Sparrow During Mating and Non-mating Periods

“…In male birds, the increase of TH concentrations is associated with the lifehistory stage with high energy demands and/or elevated BMR, such as when the testes are well developed during the mating period (3,27). To maximize fitness, birds, therefore, invest enough nutritional and energetic resources into the development and maintenance of reproductive physiology and behavior (28). During the mating stage, male birds expressing an increase up to 480-fold in the testicular mass (29) suggests the higher energy demands for testicular growth and maintenance (28,30).…”

“…To maximize fitness, birds, therefore, invest enough nutritional and energetic resources into the development and maintenance of reproductive physiology and behavior (28). During the mating stage, male birds expressing an increase up to 480-fold in the testicular mass (29) suggests the higher energy demands for testicular growth and maintenance (28,30). Meanwhile, the male bird has a pronounced swelling of the cloacal protuberance (31).…”