Interaction between cortisol and cortisol-binding protein in silver foxes (Vulpes fulvus).

1. Selection of silver foxes for domestic behaviour resulted in the parallel lowering of both cortisol and cortisol-binding protein (CBP) levels in the blood plasma. 2. During seasonal cycles (summer-winter) and after stress an increase in cortisol levels is followed by a decrease in CBP activity. 3. It is concluded that there are two types of interaction between cortisol and CBP in silver foxes: parallel changes in the process of domestication and opposite changes under the influence of environmental factors.