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
.