Antinociception mediated by the periaqueductal gray is attenuated by orphanin FQ.
Orphanin FQ or nociceptin (OFQ/N(1-17)) is a recently discovered peptide which, upon intracerebroventricular administration, reverses opioid-mediated analgesias. OFQ/N(1-17) terminals are located in the periaqueductal gray (PAG), a structure known to be involved in pain modulation, suggesting that the functional anti-opioid effects of OFQ/N(1-17) are mediated by PAG neurons. To test this, subsequent microinjections of morphine or kainic acid and OFQ/N(1-17) were made into the PAG of awake rats. Administration of OFQ/N(1-17) attenuated the tail flick inhibition produced by both morphine and kainic acid microinjection. OFQ/N(1-17) attenuation of antinociception produced by a neuroexcitant indicates that OFQ/N(1-17) reverses opioid antinociception by inhibiting PAG output neurons.
Morgan
M M
MM
Department of Psychology, Washington State University, Vancouver 98686, USA.
Grisel
J E
JE
Robbins
C S
CS
Grandy
D K
DK
D000818:Animals; D001931:Brain Mapping; D007608:Kainic Acid / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018847:Opioid Peptides / Q000008:administration & dosage / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D011957:Receptors, Opioid / Q000819:agonists; D000097629:Nociceptin
D007608:Kainic Acid; D009020:Morphine; D018847:Opioid Peptides; D011957:Receptors, Opioid; D000097629:Nociceptin