Non-invasive monitoring of adrenocortical activity in free-ranging fallow deer (Dama dama L.)
In the early classic period it was suggested by Heracleitus that a static unchanged state was not the natural condition, but rather that the capacity to undergo constant change was intrinsic to all living things. After that, Empedoeles, circa 500 BC, proposed that for living organisms to survive they require a harmonious mixture of elements. Hippocrates, around 400 BC, developed this concept further by suggesting that health is a state of harmonious balance of these elements, equating disease to a state of disharmony and introducing the concept that nature heals disease (Noysvn Fyseiw/atrui). Soon after, Epicurus extended these ideas to include among these healing forces, the mind, writing that imperturbability of mind is desirable. Claude Bernard introduced the concept of the milieu interieur or the internal physiologic environment, describing its constancy as essential in an external environment typified by its variability. Walter Cannon described Bernard's constancy as Homeostasis and identified the "fight or flight reflex," linking the adaptive response and catecholamine secretion, with extreme levels of activation-producing pathology. Selye outlined four stages of the stress response: 1) the "alarm reaction" characterized by an immediate activation of the sympathetic-adrenomedullary axis (SA); 2) a "resistance phase" characterized by hypothalamic pituitary-adrenal axis (HPA) activation; 3) a stage of adrenal hypertrophy, gastrointestinal ulceration, along with thymic and lymphoid atrophy; and 4) an exhaustion phase and finally death (1).