Highly delta selective antagonists in the RVM attenuate the antinociceptive effect of PAG DAMGO.
The present study tested the hypothesis that endogenous opioid peptides acting at the delta-opioid receptor (DOR) in the rostral ventromedial medulla (RVM) contribute to the antinociception elicited by the mu-opioid receptor (MOR) agonist DAMGO in the midbrain periaqueductal gray (PAG). Following microinjection of DAMGO into the PAG, either the highly selective DOR antagonist TIPP[psi] or the DOR2 antagonist naltriben (NTB) was microinjected into the RVM. Both TIPP[psi] (1.0 microg) and NTB (5.0 ng) significantly attenuated the analgesic effect of PAG DAMGO but had no effect when given before PAG saline. These results confirm and extend previous studies suggesting that PAG mu-opioids activate a descending system with a DOR mediated endogenous opioid link in the RVM.
Hirakawa
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Department of Neurology, Wheeler Center for the Neurobiology of Addiction, University of California at San Francisco, 94143, USA.
Tershner
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SA
Fields
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HL
D000700:Analgesics / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology*; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism* / Q000502:physiology*; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009434:Neural Pathways / Q000378:metabolism / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology*; D010487:Periaqueductal Gray / Q000378:metabolism* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors*; D017450:Receptors, Opioid, mu / Q000819:agonists; D044005:Tetrahydroisoquinolines
D000700:Analgesics; D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D044005:Tetrahydroisoquinolines; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C068868:naltrindole benzofuran; C082263:tyrosyl-1,2,3,4-tetrahydro-3-isoquinolinecarbonyl-phenylalanyl-phenylalanine; D009271:Naltrexone