Expression patterns of mineralocorticoid and glucocorticoid receptors in Bengalese finch (Lonchura striata var. domestica) brain suggest a relationship between stress hormones and song-system development.

Much evidence suggests that song traits function as an honest signal of male quality during mate choice in songbirds. Because songbirds learn vocalizations during the juvenile stage, development of the song system and song traits is affected by stressful conditions. However, it remains unknown how stressful conditions affect later song traits during development. To explore the relationship between glucocorticoids and song-system development, we performed in situ hybridization analysis of the glucocorticoid and mineralocorticoid receptors in juvenile and adult brains. The glucocorticoid receptor showed weak expression in song nuclei and strong expression in the hypothalamus, whereas the mineralocorticoid receptor showed strong song-nuclei-related expression. Thus, it appears that glucocorticoids are involved in song development directly by binding to receptors in song nuclei or indirectly by regulating sex hormones through hypothalamic hormones.