Endorphinergic systems and the response to stress.

Endogenous opioid peptides (EOPs) are extensively disturbed throughout the CNS and found in the CSF, pituitary, plasma and many peripheral organs of animals and man. Their intracerebroventricular administration produces a spectrum of morphinomimetic effects. Biochemical evidence for an acute stress-evoked release of brain, spinal cord and pituitary pools of EOPs has accumulated and the sensitivity of both adult and developing endorphinergic systems to chronic stress has been shown. EOPs are involved in the mediation of the elevations in nociceptive threshold, core temperature, exploration and grooming behaviour elicited by stress. A role in the attenuation of anxiety is also indicated. Finally an endorphinergic control of pituitary secretion and the activity of peripheral organs under stress has been demonstrated. EOPs are apparently of general importance in the response to stress in both animals and man.