Stress, Opioids, and Gastrointestinal Transit

Abstract

The behavioral and biochemical changes that occur when an animal is exposed to a stressful stimulus have generated considerable interest in many fields of study. We ourselves have been particularly interested in the way stress affects gastrointestinal function. Clinical evidence of stress-related gastrointestinal dysfunction has existed for some time, yet little is known about the etiology of stress-induced changes in intestinal motility and transit. Attempts to investigate stress-evoked alterations in these intestinal parameters in human and animal studies have led to conflicting results, possibly because different stress conditions were used. It is clear from a number of reports that the type of stress employed is a key variable determining the character of the response. For example, not all stressors result in analgesia, when it is the endpoint measured, and not all stress-induced analgesia is opioid mediated^1,2. Different stress conditions are also known to produce diverse neurochemical alterations in the central nervous system (CNS)^3–5 as well as dissimilar changes in circulating hormone levels⁶. Behavioral and biochemical responses are, therefore, very sensitive both to the type of stress applied and to other variables, such as the length and frequency of exposure to stress, the animal species, strain, gender, age, previous stress experience, housing and handling conditions, and intrinsic biologic factors, such as the light-dark and estrus cycles.