Role of the low-affinity glucocorticoid receptor in the regulation of behavior and energy metabolism in the migratory red knot Calidris canutus islandica

M M Landys*, T Piersma, M Ramenofsky, John C. Wingfield

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Plasma corticosterone increases in association with migratory flight in the red knot Calidris canutus islandica, suggesting that corticosterone may promote migratory activity and/or energy mobilization in this species. This hypothesis is supported by general effects of glucocorticoids, which include stimulation of locomotion and the mobilization of energy depots. We experimentally examined the role of elevated corticosterone levels in the migratory red knot by comparing foraging behavior, flight frequency, and plasma metabolites between vehicle-injected controls and birds treated with RU486, an antagonist to the genomic low-affinity glucocorticoid receptor (GR). We predicted that RU486 treatment would interfere with energy mobilization. However, we expected no effects on flight activity because recent studies suggest that glucocorticoids affect locomotion through a nongenomic receptor. Finally, because glucocorticoids exert permissive effects on food intake, we postulated that RU486 treatment in the red knot would interfere with feeding. Results were consistent with the latter prediction, suggesting that the GR participates in the promotion of hyperphagia, the intense feeding state that is characteristic of the migratory condition. RU486 treatment did not affect flight frequency, suggesting that corticosterone may support migratory activity through a receptor other than the GR. Energy metabolism (as determined through plasma metabolites) was also unaffected by RU486, possibly because energetic demands experienced by captive birds were low.

Original languageEnglish
Pages (from-to)658-668
Number of pages11
JournalPhysiological and Biochemical Zoology
Volume77
Issue number4
DOIs
Publication statusPublished - 2004

Keywords

  • ZONOTRICHIA-LEUCOPHRYS-GAMBELII
  • WHITE-CROWNED SPARROWS
  • CORTICOSTERONE LEVELS
  • PASSERINE BIRDS
  • BASE-LINE
  • URIC-ACID
  • SEASONAL-CHANGES
  • STRESS-RESPONSE
  • SECRETION
  • MECHANISM

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