The orphan opioid receptor and its endogenous ligand — nociceptin/orphanin FQ

[Nphe1]‐Nociceptin (1‐13)‐NH2, a nociceptin receptor antagonist, reverses nociceptin‐induced spatial memory impairments in the Morris water maze task in rats

“…Moreover, in situ hybridization and immunohistochemical studies, in rodents, have demonstrated that both OP 4 / nociceptin mRNA and receptor protein are found in high concentrations in the hippocampus, brainstem and cortex, areas of the brain involved in higher functions including learning and memory processing (Henderson & McKnight, 1997;Meunier, 1997;Darland et al, 1998).…”

Further characterization of the ORL1 receptor‐mediated inhibition of noradrenaline release in the mouse brain in vitro

“…A fourth type of opioid receptor, termed opioid receptor-like 1 (ORL 1 ) (Mollereau et al, 1994), orphan opioid (Henderson & McKnight, 1997) or, tentatively, OP 4 receptor (Hamon, 1998), has been cloned by several groups in 1994 (for review, see Henderson & McKnight, 1997;Meunier, 1997). The heptadecapeptide nociceptin (also termed orphanin FQ) has been identi®ed as endogenous ligand at this receptor (Meunier et al, 1995;Reinscheid et al, 1995).…”

“…The heptadecapeptide nociceptin (also termed orphanin FQ) has been identi®ed as endogenous ligand at this receptor (Meunier et al, 1995;Reinscheid et al, 1995). Despite the high structural resemblance of the ORL 1 receptor to the classical opioid receptors, most of the ligands at the classical opioid receptors have very low a nity for the ORL 1 receptor; another striking di erence to the classical opioid receptors is the fact that nociceptin elicits a hyperalgetic rather than an analgetic response in rodents (for review, see Henderson & McKnight, 1997;Meunier, 1997).…”

“…Nociceptin inhibits transmitter release (determined directly or via the endorgan response) in a series of peripheral tissues, including the guinea-pig ileum and the rat and mouse vas deferens (for review, see Henderson & McKnight, 1997;Meunier, 1997). With respect to the CNS, Vaughan et al (1997) found that nociceptin, at a presynaptic site, inhibited the evoked fast GABAergic and glutamatergic postsynaptic currents in rat periaqueductal gray slices.…”

Characterization of Specific [3H]Nociceptin Binding in Rat Brain and Spinal Cord.

“…Nociceptin itself has high homology with opioid peptides, particularly dynorphin A, the endogenous ligand of the k-opioid receptor, but this peptide exhibits very low binding affinity for opioid receptors. 8) Pharmacological studies have shown that nociceptin may be involved in a wide variety of physiological functions: pain and analgesia, 9) opioid tolerance, 10) learning and memory, 11) locomotion, 12) feeding, 13) stress and anxiety 14) and neuronal differentiation 15) in the central nervous system. It may also produce effects on the cardiovascular system, 16,17) urogenital tract 18,19) and immune system 20) in the periphery.…”