Cloned mouse δ-subtype opioid receptor (DOR1) was expressed in Xenopus oocytes to study the signal transduction. Opioid δ-agonists evoked a calcium-dependent chloride current in oocytes injected with mRNA derived from DOR1, together with that from the α subunit of Gi1. The δ-agonist-induced current was blocked by naltrindol, a δ-specific antagonist. The δ-agonist evoked no or very weak currents in oocytes with the α subunit of Gq or Go. These findings indicate the functional coupling between the opioid δ-receptor and phospholipase C through an activation of Gi.
