CHARACTERIZATION OF A DELTA-OPIOID RECEPTOR IN RAT PHEOCHROMOCYTOMA CELLS

In one subclone of PC12 pheochromocytoma cells, PC12h, the levels of d elta opioid receptors markedly increase in response to nerve growth fa ctor (NGF). This increase, as assessed by [H-3]diprenorphine binding, is found only under specific culture conditions. NGF treatment of PC12 h cells also results in the induction of delta opioid receptor (DOR-I) mRNA. The time course for NGF induction of mRNA and protein is simila r, although the levels of mRNA increase approximately 5-fold, whereas the levels of receptor increase only 2-fold. Competition studies with selective delta ([D-Pen(2,5)]-enkephalin, DPDPE), mu ([D-Ala(2),N-Me-P he(4),Gly-ol(5)]-enkephalin, DAMGO) and kappa -N-[2-(1-pyrrolidinyl)-c yclohexyl]-benzenacetamide methansulfonate salt, U50,488) opioid agoni sts to displace [H-3]diprenorphine confirm that the delta subtype of o pioid receptor is present on PC12h cells. The delta opioid receptor is coupled functionally, as indicated by agonist inhibition of forskolin -stimulated cAMP accumulation in a naloxone-reversible manner. Finally , the delta opioid receptor was cloned from PC12h cells. The sequence was identical with that described previously for the rat clone. The PC 12h cell line thus provides a model system in which to study regulatio n of delta opioid receptors.