Chicken domestication changes expression of stress-related genes in brain, pituitary and adrenals.

Domesticated species have an attenuated behavioral and physiological stress response compared to their wild counterparts, but the genetic mechanisms underlying this change are not fully understood. We investigated gene expression of a panel of stress response-related genes in five tissues known for their involvement in the stress response: hippocampus, hypothalamus, pituitary, adrenal glands and liver of domesticated White Leghorn chickens and compared it with the wild ancestor of all domesticated breeds, the Red Junglefowl. Gene expression was measured both at baseline and after 45 min of restraint stress. Most of the changes in gene expression related to stress were similar to mammals, with an upregulation of genes such as , and in hippocampus and hypothalamus and , and in adrenal glands. We also found a decrease in the expression of in the pituitary of chickens after stress, which could be involved in negative feedback regulation of the stress response. Furthermore, we observed a downregulation of and C in the pituitary following stress, which could be a potential link between stress and its effects on reproduction and growth in chickens. We also found changes in the expression of important genes between breeds such as in the hypothalamus, and in the pituitary and and in the adrenal glands. These results suggest that the domesticated White Leghorn may have a higher capacity for negative feedback of the HPA axis, a lower capacity for synthesis of ACTH in the pituitary and a reduced synthesis rate of corticosterone in the adrenal glands compared to Red Junglefowl. All of these findings could explain the attenuated stress response in the domesticated birds.