Involvement of mu- and delta-opioid receptors in the antinociceptive effects induced by AMPA receptor antagonist in the spinal cord of rats.
The present study was performed to explore the involvement of opioid receptors in the antinociception induced by a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor antagonist in rats. The hindpaw withdrawal latency (HWL) to noxious thermal and mechanical stimulation was assessed by hot plate test and the Randall Selitto Test. Intrathecal injection of 20 nmol of 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo[f]quinoxaline-7-sulfonamide (NBQX) disodium, a competitive AMPA receptor antagonist, increased significantly the HWLs to both thermal and mechanical stimulation in rats. The increased HWLs induced by NBQX were dose-dependently attenuated by the opioid receptor antagonist naloxone, while naloxone itself had no marked influences on the HWL of rats. Furthermore, the increased HWLs induced by NBQX were inhibited by the mu-opioid antagonist beta-funaltrexamine (beta-FNA) or the delta-opioid antagonist naltrindole, but not by the kappa-opioid antagonist nor-binaltorphimine (nor-BNI). The results suggest that mu- and delta-opioid receptors, not kappa-opioid receptor, are involved in the antinociception induced by AMPA antagonist in the spinal cord of rats.
Kong
Ling-Ling
LL
Laboratory of Neurobiology and National Key Laboratory of Biomembrane and Membrane Biotechnology, College of Life Sciences, Peking University, Beijing 100871, PR China.
Yu
Long-Chuan
LC
D000700:Analgesics / Q000037:antagonists & inhibitors / Q000627:therapeutic use*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D008297:Male; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D010147:Pain Measurement / Q000379:methods; D010812:Physical Stimulation / Q000379:methods; D011810:Quinoxalines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000502:physiology; D017465:Receptors, Opioid, delta / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects* / Q000503:physiopathology; D014851:Wakefulness
D000700:Analgesics; D011810:Quinoxalines; D018091:Receptors, AMPA; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; C051844:norbinaltorphimine; D009271:Naltrexone; C024524:beta-funaltrexamine; C055382:naltrindole