Characterization of ZFOR1, a putative delta-opioid receptor from the teleost zebrafish (Danio rerio)

ZFOR1 is a putative opioid receptor from zebrafish brain which has 66% homo logy with the mammalian delta-opioid receptor. When expressed in HEK293 cel ls ZFOR1 bound the non-selective opioid antagonist [H-3]diprenorphine with high affinity. However, the binding of this ligand was not readily displace d by opioids selective for mu, delta or kappa opioid receptors (affinities > 1000 nM). Rather non-selective ligands showed good affinity, as did the n on-peptide delta-ligand BW373U86 (Ki 69 nM), the delta-antagonist naltrindo le (Ki 28 nM) and the peptide P-endorphin (Ki 37 nM). Agonist binding to th e receptor encoded by ZFOR1 receptor stimulated the binding of [S-35]GTP ga mma S confirming coupling to G proteins. Study of the receptor should contr ibute to understanding of the evolution of the opioid system. (C) 2000 Else vier Science Ireland Ltd. All rights reserved.