Expression of functional delta opioid receptors in Xenopus oocytes

Functional delta opioid receptors were expressed in Xenopus oocytes following injection of poly(A+)RNA isolated from the mouse neuroblastoma X rat glioma hybrid cell line, NG108-15. Oocytes coinjected with in vitro transcribed beta 2-adrenergic receptor mRNA and NG108-15 cell mRNA had 3-fold elevated cAMP levels following isoproterenol treatment. Application of delta opioids to these oocytes caused dose-dependent inhibition of isoproterenol-induced increase of cAMP, which was antagonized by naltrexone. This is the first demonstration of the expression of opioid receptors in Xenopus oocytes. The ability to assay expression of delta opioid receptors functionally coupled to the inhibition of adenylate cyclase in Xenopus oocytes following injection of exogenous mRNA will provide a system to investigate the relationship of molecular structure to function of opioid receptors.