Mu-opioid receptor in the nucleus submedius: involvement in opioid-induced inhibition of mirror-image allodynia in a rat model of neuropathic pain.
The current study investigated the roles of various subtypes of opioid receptors expressed in the thalamic nucleus submedius (Sm) in inhibition of mirror-image allodynia induced by L5/L6 spinal nerve ligation in rats. Morphine was microinjected into the Sm, which produced a dose-dependent inhibition of mirror-image allodynia; this effect was antagonized by pretreatment with non-selective opioid receptor antagonist naloxone. Microinjections of endomorphin-1 (mu-receptor agonist), or [D-Ala(2), D-Leu(5)]-enkephalin (DADLE, delta-/mu-receptor agonist), also inhibited mirror-image allodynia, and these effects were blocked by the selective mu-receptor antagonist, beta-funaltrexamine hydrochloride. The DADLE-induced inhibition, however, was not influenced by the delta-receptor antagonist naltrindole. The kappa-receptor agonist, spiradoline mesylate salt, failed to alter the mirror-image allodynia. These results suggest that Sm opioid receptor signaling is involved in inhibition of mirror-image allodynia; this effect is mediated by mu- (but not delta- and kappa-) opioid receptors in the rat model of neuropathic pain.
Wang
Jun-Yang
JY
Department of Immunology and Pathogenic Biology, Xi'an Jiaotong University School of Medicine, Xi'an, Shaanxi 710061, People's Republic of China.
Zhao
Mei
M
Huang
Fen-Sheng
FS
Tang
Jing-Shi
JS
Yuan
Yu-Kang
YK
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004195:Disease Models, Animal; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D006930:Hyperalgesia / Q000188:drug therapy*; D008026:Ligation; D008297:Male; D009020:Morphine / Q000627:therapeutic use*; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009437:Neuralgia / Q000188:drug therapy* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000502:physiology*; D013127:Spinal Nerves / Q000502:physiology; D013787:Thalamic Nuclei / Q000378:metabolism*
D009292:Narcotic Antagonists; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; C105293:endomorphin 1; D009270:Naloxone; D009271:Naltrexone; D016308:Enkephalin, Leucine-2-Alanine; C024524:beta-funaltrexamine; D009020:Morphine; C055382:naltrindole