[Dual regulation by delta opioid receptor agonists on the delayed rectified potassium channels in NG108-15 cells].

OBJECTIVE: To investigate the dual effects by the delta opioid receptor agonists DPDPE on the delayed rectified potassium channels in NG108-15 cells. METHODS: A series of outward currents were evoked in NG108-15 cells by depolarizing voltage from -50 mV to +80 mV at holding potential of -90 mV. These currents were delayed rectified potassium currents. Relatively selected delta opioid receptor agonists DPDPE of higher and lower concentrations were used to modulate the delayed rectified K+ current in NG108-15 cells. Opioid receptor antagonist Naloxone (NAL) and relatively selected delta opioid receptor antagonist Naltrindole (NTI) were used in the present experiments for the characterization of the actions of opioid receptors. RESULTS: The relatively higher concentrations of delta opioid receptor agonist DPDPE (> or = 10(-6) mol/L) significantly increased the amplitude of the delayed rectified K+ current. On the contrary, the relatively lower concentrations of DPDPE (< or = 10(-12) mol/L) decreased the amplitude of the delayed rectified K+ current (P < 0.05). Furthermore both the increase and decrease were time-dependent. CONCLUSIONS: delta opioid receptor agonist has dual regulatory effects on the delayed rectified potassium channels in NG108-15 cells.