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Proceedings for Pain Management and Humane Endpoints

Assessment of Pain and Distress in Laboratory Animals

Jeri Sechzer, AM, PhD
Pace University, New York, NY

The research community has become increasingly aware of the ethics of animal pain and distress and the effect on the validity of experimental data. The Institute of Laboratory Animal Resources of the National Research Council has published "Recognition and Alleviation of Pain and Distress in Laboratory Animals". The concept of the project was organized about the relationship of homeostasis, stress, and distress. Homeostasis was defined as the tendency of the body to maintain physiological and behavioral equilibrium; Stress, the effect produced by external or internal factors called stressors; and Distress as an aversive state in which the animal is unable to adapt successfully to the stressors imposed on it.

Two models of distress were developed: 1) Distress Induced by Pain and 2) Distress Not Induced by Pain. Stressors leading to stress were identified and classified as external (physical and environmental) and internal (physiological and psychological) of which pain is an important component. Stress by itself does not usually pose a threat to the animal as long as it can maintain an adaptive state of homeostasis. When this is no longer possible and the animal cannot adapt to the stress the animal will enter a state of distress, its physiology and behavior will then become maladaptive.

Recent data in animals have shown that pain and inhibition of pain differs in males and females and that estrogen dependent pathways in females play an important role in analgesia. It has also been suggested that some analgesics may produce more pain relief in males than females.

Details of models of pain and distress will be described and the effect of distress and maladaptive behaviors on the health and well-being of the animal and on experimental outcome will be discussed. Recent factors concerning the assessment of pain and distress in male and female animals will also be explored.