The opioid receptor-like1 receptor (ORL1), an orphan receptor whose human and murine complementary DNAs, has been characterized recently. ORL1 transcripts are particularly abundant in the central nervous system. We demonstrated that ORL1 expressed in human neuroblastoma SK-N-SH and SH-SY5Y cell lines by radioligand binding assay, reverse transcription polymerase chain reaction (RT-PCR) and Northern analysis in the present study. Stimulation with ORL1 specific agonist, nociceptin/orphanin FQ, increased [35S]GTP gamma S binding to SK-N-SH cell membranes (EC50 = 14 +/- 0.45 nM), and attenuated forskolin-stimulated accumulation of cellular cAMP (EC50 = 0.80 +/- 0.45 nM), indicative that activation of ORL1 activates G proteins and inhibits adenylyl cyclase. Activation of ORL1 receptor was also accessed using CHO:hORL1 cell line by microphysiometer. Treatment of nociceptin/orphanin FQ increased extracellular acidification rate significantly.