Opiate modulating properties of nociceptin/orphanin FQ

The recently discovered peptide nociceptin/orphanin FQ (N/OFQ) and its rece ptor NOR share many structural similarities with the opioid peptides and th eir receptors. The anatomical distributions of N/OFQ and NOR are similar to those of opioid peptides and receptors. In addition, NOR and opiate recept ors couple via the same G-proteins to similar effectors, such as Ca2+ chann els, K+ channels, adenylyl cyclase, and several protein kinases. Thus, the behavioral effects of N/OFQ have been investigated in the context of known opiate effects, and a possible connection has been sought between the effec ts of these two homologous signaling systems. Originally characterized as a nociception-producing peptide, N/OFQ has now been shown to have diverse ef fects on nociception, as well as effects on many other behaviors. With rega rd to nociception, the peptide has been reported to produce hyperalgesia, r eversal of opioid-mediated analgesia, analgesia, and allodynia. N/OFQ also has effects on other behaviors, such as locomotion, feeding, anxiety? spati al attention, reproductive behaviors, and opiate tolerance. The relationshi p between opiates and N/OFQ is strengthened by the fact chat opiates also a ffect these behaviors. However, the exact nature of the relationship of N/O FQ with opiates-opiate-like versus antiopiate-remains controversial. This r eview will detail the diverse effects of N/OFQ and suggest that this peptid e, like other putative antiopiate peptides, can be described as 'opiate mod ulating.' (C) 2000 Elsevier Science Inc. All rights reserved.