Modification of dopamine release by nociceptin in conscious rat striatum

Nociceptin (NOC), an endogenous ligand for the orphan receptor ORL1, has recently been recognized as a neuropeptide. We used brain microdialysis and on-line high performance liquid chromatography to examine the effect of NOC on the basal outflow of dopamine (DA) and its metabolite in the freely moving rat striatum in vivo. The percent change of DA release induced by NOC at concentrations of 10-6 and 10-5 M were 383% and 398%, respectively. This effect of NOC was attenuated by naloxone, suggesting that NOC activates classic (micro, delta, kappa) receptors in a very little way. These data indicates that NOC may act as a neuropeptide which enhances DA release from the striatum of rat brain via an opioid receptor.