Summary: Hart (2012)

 The ability to accurately determine an animal's level of pain and stress is crucial for the correct design and implementation of various handling and experimental procedures. Hart (2012) suggests that the quantification of physiological neuroendocrine responses could allow for an objective measure of associated stress and pain than behavioural observations alone. She notes that the hypothalamic-pituitary-adrenal (HPA) axis plays a large role in the neuroendocrine response  of an animal to various types of stressors (environmental,  emotional  and  physiological). This system is integrated with the production of cortisol, a glucocortiocoid stress hormone commonly used in behavioural studies as a measure of stress. Hart (2012) suggests that using the concentration of cortisol as a measure of objective stress assessment could be misinterpreted, as aspects of HPA physiology are often overlooked. She notes that using plasma cortisol concentration as a measure of stress can be useful in some cases, but notes that investigators should take into account the unique variable nature of HPA axis activation.