Characterization of a new duplicate delta-opioid receptor from zebrafish.

A new full-length cDNA (ZFOR4) that encodes an opioid receptor has been isolated from the teleost zebrafish. The encoded polypeptide is 375 amino acids long and shows high sequence similarity to other delta-opioid receptors, including ZFOR1, the other delta-opioid receptor from zebrafish previously characterized by us. In situ hybridization studies have revealed that ZFOR4 mRNA is highly expressed in particular brain areas that coincide with the expression of the delta-opioid receptor in other species.