Role of nociceptin in the modulation of nociception in the arcuate nucleus of rats.
Neuropeptide nociceptin/orphanin FQ is the endogenous ligand for the opioid-receptor-like receptor 1 (ORL1), mediating essential functions in the central and peripheral nervous systems. The present study was performed to investigate the role of nociceptin and ORL1 receptor in nociception and morphine-induced antinociception in the arcuate nucleus of hypothalamus in rats. Hindpaw withdrawal latencies (HWL) were measured by hot-plate and Randall Selitto tests. The HWL to both thermal and mechanical stimulation decreased significantly after intra-arcuate nucleus injection of nociceptin in a dose-dependent manner. The effect of nociceptin was blocked significantly by subsequent intra-arcuate nucleus administration of [Nphe(1)]nociceptin(1-13)-NH(2), an ORL1 receptor antagonist. Furthermore, an intra-arcuate nucleus injection of nociceptin dramatically attenuated the antinociceptive effect induced by morphine either injected in the same site or applied intraperitoneally. These results suggest that nociceptin in the arcuate nucleus induces a hyperalgesic effect by acting on ORL1 receptors. The present study also demonstrates an interaction between nociceptin and opioids in the arcuate nucleus of the hypothalamus.
Li
Ning
N
Laboratory of Neurobiology, College of Life Sciences, Peking University, Beijing 100871, P.R. China.
Wei
Shi-Yi
SY
Yu
Long-Chuan
LC
Moriyama
Kumi
K
Mitchell
James
J
Palmer
Pamela Pierce
PP
D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006358:Hot Temperature / Q000009:adverse effects; D008297:Male; D009020:Morphine / Q000008:administration & dosage; D018847:Opioid Peptides / Q000008:administration & dosage*; D010147:Pain Measurement / Q000187:drug effects* / Q000379:methods; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D000097629:Nociceptin
D009020:Morphine; D018847:Opioid Peptides; D000097629:Nociceptin