Effects of in ovo injection of serotonin on behavior and hypothalamic genes expression in post hatch-chicks

Abstract

Abstract Serotonin (5-HT) is essential for neuronal development and behavioral regulation. Serotonin, upon in ovo administration, has been previously reported to modulate aggressive behavior in avian species, however it still remains unknown if maternal serotonin affects chick behavior through hypothalamic gene expression. We injected an equal volume of saline (control) and either a 5\u2009μg (low) or a 15\u2009μg (high) dose of 5-HT into embryos on embryonic day 11 (E11). The blood concentration of 5-HT was determined in chicks on post-hatching D3 (Day 3) and D45. The behavioral fear and aggression were analyzed at D10 and D52. In isolation test, the latency to vocalize and walk, the duration of vocalizations and walking were recorded. Hypothalamic expression of genes related to the serotonin pathway and the methylation status of hypothalamic 5-HT 1A receptor (5-HTR1A) were measured at D56. Chicks treated with embryonic 5-HT exhibited a certain decrease in the degree of fear as determined by the duration of vocalizations (p