BETA-ENDORPHIN IN THE BRAIN - A ROLE IN NOCICEPTION

We have known the endogenous opioid peptide beta-endorphin for 20 year s. Surprisingly, our knowledge of the physiological role of this pepti de and its receptors in modulation of pain perception is still fragmen tary. Whereas most studies have tried to elucidate the physiological r ole of beta-endorphin by reversing evoked responses by the opioid anta gonist naloxone, this review focuses on quantification of release of b eta-endorphin in the brain as the approach to define physiological and pathophysiological roles of beta-endorphin in relation to nociception . Using a lateral ventricle-cisterna magna perfusion model in the anes thetized rat, it was shown that depolarization of neurons in the arcua te nucleus of the hypothalamus, where beta-endorphin is produced, was followed by release of beta-endorphin to the cerebrospinal fluid compa rtment. Intense activation of spinal nociceptive pathways by intrathec al capsaicin injections also led to beta-endorphin release. It is conc luded that there may still be good reason to quantify beta-endorphin i n human cerebrospinal fluid to elucidate the role of beta-endorphin in pain perception. (C) Acta Anaesthesiologica Scandinavica 41 (1997).