Open Collections

Gray, Sofia L.

University of British Columbia

Adult male song sparrows (Melospiza melodia) display territorial aggression year-round. Territoriality is supported by gonadal sex steroids during the breeding season but might be supported by brain-derived sex steroids during the non-breeding season. Juvenile (hatch-year) male song sparrows also defend territories during the non-breeding season despite having immature testes and low plasma testosterone levels. Juvenile males therefore represent an excellent model to investigate the modulatory role of neurosteroids on aggression. Here, free-living non-breeding juvenile males experienced a 10-min simulated territorial intrusion (STI) or control condition. Blood and brain were collected, and steroids were quantified in blood and microdissected brain regions via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Juveniles were robustly aggressive during an STI. Juveniles were equally as aggressive or more aggressive than non-breeding adults. Androgens and estrogens were low or non-detectable in blood and brain regardless of social context. After an STI, progesterone and glucocorticoids were elevated in the blood and brain in a region-specific manner. Together, these data suggest that juvenile non-breeding aggression might be rapidly modulated by adrenal-derived or brain-derived progestogens and glucocorticoids. These rapid changes in steroid levels might impact behaviourally relevant neural circuits and mobilize energy stores from peripheral organs. To our knowledge, we are the first to investigate the interplay between developmental life-stage and social context at the behavioural and steroidal level in an avian model. This work provides insight into distinct endocrine and neuroendocrine mechanisms of social behaviour in a juvenile songbird that might extend to other vertebrates.

Text

2022-08-12

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/82341

Psychology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/