Meeting Abstract
The activity of a hypothalamus-pituitary-adrenal (HPA) axis is regulated by a conflict between beneficial and harmful actions of its main effector hormones, including corticosterone (CORT). A strong increase of blood CORT is beneficial when overcoming short, intense challenges, but can be harmful when the HPA axis remains stimulated for a long time. Therefore, adjustments of the HPA axis activity may participate in evolution of adaptation to certain challenges. Experimental evolution offers an efficient tool to approach the problem. We asked whether the HPA axis activity differs between lines of bank voles (Myodes glareolus) selected in three directions: high aerobic exercise metabolism (A), predatory behavior (P), ability to cope with low-quality herbivorous diet (H), and unselected control lines (C). We measured baseline CORT in blood of animals from three groups: challenged with chronic mild stress (CMS), challenged with increased metabolic demands of thermoregulation, and non-challenged. The thermoregulatory burden increased baseline CORT, but the effect did not differ among the selection directions. The response to CMS was altered by selection: baseline CORT increased in A and P lines, but remained unchanged in C and H lines. In conclusion, adaptation to challenges requiring burst activity of the HPA axis or its high sensitivity to stimuli can result in a higher susceptibility to chronic stress.
