ISOLATION OF A HUMAN KAPPA-OPIOID RECEPTOR CDNA FROM PLACENTA

By using a mouse delta opioid receptor cDNA as a probe, a kappa opioid receptor gene was isolated from a human genomic library. Reverse transcriptase/PCR was subsequently used to isolate the corresponding cDNA from human placenta mRNA. Characterization of the cloned receptor with a kappa agonist in transfected COS-7 cells, revealed a Kd Of 0.67nM, which is similar to rodent kappa 1 receptors. In competition binding experiments, non-kappa agonists had k(i)s > 1000nM. Furthermore, when expressed in COS-7 cells, the kappa receptor is negatively linked to cAMP. A Northern blot showed the presence of two transcripts, 6 and 7 kB in size, in both placenta and brain mRNA, which hybridized to the kappa cDNA. (C) 1994 Academic Press, Inc.