Nociceptive stimulus induces release of endogenous beta-endorphin in the rat brain.
The hypothesis that the naturally occurring analgesic peptide, beta-endorphin, is released in the brain in response to pain had never been directly validated. In this study, we applied a brain microdialysis method for monitoring beta-endorphin release in vivo, to test this hypothesis in the brains of conscious, freely moving rats. Herein we first show that endogenous beta-endorphin can be measured in vivo in the brain under physiological conditions. Upon induction of a nociceptive stimulus by injection of formalin into the hind-paws of rats, the extracellular levels of beta-endorphin in their arcuate nucleus increased by 88%, corresponding to their nociceptive response. This direct evidence for the release of endogenous beta-endorphin in the brain in response to nociceptive stimulus indicates a possible mechanism for organisms to cope with pain.
Zangen
A
A
Department of Life Science, Bar-Ilan University, Ramat-Gan, Israel.
Herzberg
U
U
Vogel
Z
Z
Yadid
G
G
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism* / Q000502:physiology; D005557:Formaldehyde; D008297:Male; D017551:Microdialysis; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D001615:beta-Endorphin / Q000378:metabolism*
D005557:Formaldehyde; D001615:beta-Endorphin; D011189:Potassium Chloride