Post-natal glucocorticoid elevation affects GnRH-induced luteinizing hormone concentration in female house sparrows
Résumé
Most non-mammalian studies investigating the long-term effects of early-life stressor exposure on endocrine
regulation have focused on the hypothalamic-pituitaryadrenal (HPA) axis. However, the hypothalamic-pituitarygonadal
(HPG) axis may more directly affect fitness by regulating reproduction. Changes in HPG axis regulation
could allow vertebrates to adaptively mitigate negative effects of early-life stressor exposure. However, only a
few studies have examined long-term effects of early-life stressor experience on the HPG axis, and these have
found mixed results. Here, we evaluate long-term effects of post-natal corticosterone exposure on the HPG axis in
adult female house sparrows (Passer domesticus). We elevated circulating corticosterone non-invasively in wild
nestling house sparrows between 8 and 11 days post-hatching, and then brought birds into captivity at fledging.
Early in their first breeding season (ages 285-353d post-hatching), females were given a gonadotropin releasing
hormone (GnRH) challenge. We found that early-life corticosterone exposure interacted with current condition
such that females exposed to elevated post-natal corticosterone had higher baseline and GnRH-induced luteinizing
hormone (LH) concentration than control females, but only if they had a high mass. Our results suggest
that female house sparrows may mitigate negative impacts of early-life corticosterone exposure by investing in
early reproduction, but only when current energetic condition allows.