Modification of acetylcholine release by nociceptin in conscious rat striatum

Abstract

Nociceptin (NOC), an endogenous ligand for the orphan opioid receptor ORL 1 (ORL 1), has recently been recognized as a neuropeptide. We used brain microdialysis and on-line high performance liquid chromatography (HPLC) to examine the effect of NOC on the basal outflow of acetylcholine (ACh) in the freely moving rat striatum in vivo. ACh release was reduced by nociceptin at a concentration of 10 −5 M to 79% of control release. This effect of NOC was attenuated by [Phe 1Ψ(CH 2–NH)Gly 2]nociceptin-(1-13)–NH 2 (PheΨ), suggesting that NOC activates the ORL 1 receptor and (PheΨ) acts as an antagonist on ORL 1 in rat striatum in vivo. These findings indicate that NOC may act as a neuropeptide which inhibits ACh release in the striatum via ORL 1.