To explore electrophysiological properties of the δ-Opioid receptors artificially expressed in the mammalian cell, effect of an opioid agonist DPDPE (1 μM) on the voltage-sensitive outward currents was examined in the HEK293 (human embryonic kidney) cells transfected with δ-Opioid receptor cDNA cloned from NG-108-15 (neuroblastoma X glioma hybrid) cDNA library. Also studied were effects of 8-bromo-cyclic AMP and naloxone on DPDPE-induced changes in the voltage sensitive outward current. The voltage sensitive outward currents were recorded using perforated patch technique at room temperature. In the non-transformed HEK293 cells, DPDPE did not alter voltage sensitive outward current, indicating that no native δ-Opioid receptor had been developed. However, (1 μM) DPDPE remarkably increased the voltage sensitive outward current in the transformed HEK293 cells. The increment in voltage sensitive outward current peaked in 7 ~ 10 minutes after DPDPE application, and the maximum DPDPE-activated outward current (313.1±12.3 pA) was recorded when the membrane potential was depolarized to +70mv. Following pretreatment of the transformed HEK293 cells with 1 mM 8-bromo-cyclic AMP, DPDPE failed to increase the voltage sensitive outward currents. On the other hand, naloxone completely abolished DPDPE-activated voltage sensitive outward current in the transformed HEK293 cells. The results of present study suggest that in the transformed HEK293 cells an activation of the δ-Opioid receptors by an opioid agonist DPDPE increases the voltage-sensitive potassium current as a result of decrement in cyclic AMP level.