[Opioid peptides in the dynamics of "physiological" and "pathological" stress]

Clinical studies showed that short-term "physiological" stress (bicycle ergometry) did not cause increase of the blood plasma enkephalin content. Moderate-term (60-minute) stress, according to O. Desiderato, causes a rise of the blood enkephalin level in rats. It is supposed that such a reaction of the opioid system is characteristic of borderline conditions between normal and pathological states in stress. Severe "pathological" stress (myocardial infarction, experimental coronary occlusion, 6-hour stress after O. Desiderato) in rats led to a decrease of the concentration of enkephalins in the blood and disorders of their secretion and storage in the adrenals. It is suggested that changes of the activity of the opioid system are a predictor of the transition of a "physiological" stress to a "pathological" stress.