Characterization of a delta opioid receptor in rat pheochromocytoma cells

In one subclone of PC12 pheochromocytoma cells, PC12h, the levels of delta opioid receptors markedly increase in response to nerve growth factor (NGF). This increase, as assessed by [3H]diprenorphine binding, is found only under specific culture conditions. NGF treatment of PC12h cells also results in the induction of delta opioid receptor (DOR-1) mRNA. The time course for NGF induction of mRNA and protein is similar, although the levels of mRNA increase approximately 5-fold, whereas the levels of receptor increase only 2-fold. Competition studies with selective delta ([D-Pen2,5]-enkephalin, DPDPE), mu ([D-Ala2,N-Me-Phe4,Gly-ol5]- enkephalin, DAMGO) and kappa (trans-[+/-]-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzenacetamide methansulfonate salt, U50,488) opioid agonists to displace [3H]diprenorphine confirm that the delta subtype of opioid 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 PC12h cell line thus provides a model system in which to study regulation of delta opioid receptors.