Agonistic effects of the opioid buprenorphine on the nociceptin/OFQ receptor

The nociceptin/orphanin FQ (N/OFQ) receptor (e.g. the human ortholog ORL1) has been shown to be pharmacologically distinct from classic opioid recepto rs. Recently, we have identified buprenorphine as a full ORL1 agonist using a reporter gene assay. For further functional analysis, buprenorphine's ef fects on ORL1 receptors were investigated using a K+ channel (GIRK1) assay in Xenopus oocytes and GTP gamma S assay in CHO-K1 membrane preparations. T n both assays, buprenorphine behaved as a partial agonist compared to nocic eptin itself. The N/OFQ agonism of buprenorphine might contribute to action s of buprenorphine in pain models in vivo beside its mu- or kappa-opioid re ceptor mediated effects. (C) 2000 Elsevier Science Inc. All rights reserved .