Endomorphin-1 reduces carrageenan-induced fos expression in the rat spinal dorsal horn.
Intraplantar injection of carrageenan induced significant Fos expression in the superficial and deep spinal dorsal horn at the L(4)-L(5)segments and extensive peripheral edema of the ipsilateral foot in rats. Intraplantar injection of endomorphin-1, endogenous ligand for mu opioid receptor, in the same region produced dose-dependent reduction of carrageenan-induced Fos expression and peripheral edema, which were completely blocked by co-administration of intraplantar injection of naloxone (20 microgram). The systemic injection of the highest dose of endomorphin-1 (50 microgram) had no significant reductory effect on Fos expression and peripheral edema. These results further provided a strong evidence for involvement of mu opioid receptor in peripheral analgesia, particularly in inflammation pain.
Jin
S
S
Shanghai Brain Research Institute, Chinese Academy of Sciences, Shanghai, 200031, China. zhoa@iris.shlc.ac.cn
Lei
L
L
Wang
Y
Y
Da
D
D
Zhao
Z
Z
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D002351:Carrageenan; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*; D010146:Pain / Q000378:metabolism; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009842:Oligopeptides; D016760:Proto-Oncogene Proteins c-fos; C105293:endomorphin 1; D009270:Naloxone; D002351:Carrageenan