Abstract
First isolated some 10 years ago as the endogenous ligand for the "orphan opioid receptor" (ORL-1, now designated NOP), nociceptin/orphanin FQ (N/OFQ) has proved to be a potent inhibitory neuropeptide found across the neuraxis. Because of the homologies between opioids and N/OFQ, functional studies of this peptide have focused most heavily on pain and analgesia. This behavioral literature has been marked by a lack of consistency across laboratories, but much of the data can be explained by considering the potent inhibitory actions of N/OFQ in well-defined modulatory circuits. Presently, the most closely studied such circuit is the rostral ventromedial medulla (RVM), where administration of N/OFQ can block opioid analgesia (by inhibiting opioid-activated pain-inhibiting neurons), but under other conditions produces apparent hypoalgesia (by inhibiting pain-facilitating neurons). The net behavioral effect of N/OFQ in the RVM thus depends on whether experimental conditions are such that the pain-facilitating or pain-inhibiting neurons are active at the time the peptide is given. An important recent finding is that N/OFQ antagonists have antinociceptive properties when given supraspinally. Although the likelihood of interactions between stress and analgesia systems must be considered in interpreting these data, they suggest that N/OFQ antagonists have potential as clinically useful analgesic drugs.
Original language | English (US) |
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Pages (from-to) | 3127-3132 |
Number of pages | 6 |
Journal | Life Sciences |
Volume | 77 |
Issue number | 25 |
DOIs | |
State | Published - Nov 4 2005 |
Keywords
- Circuit-analysis
- Orphanin FQ
- Pain
- Stress
ASJC Scopus subject areas
- General Pharmacology, Toxicology and Pharmaceutics
- General Biochemistry, Genetics and Molecular Biology