This study investigated the presence of neuropeptide FF (NPFF) receptors on F-11 cells, a hybridoma derived from rat dorsal root ganglia (DRG) and mouse neuroblastoma. Binding experiments revealed a low density (4 fmol/mg) of high affinity (0.5 nM) [(3)H]-EYF binding sites in these cells. The whole-cell planar patch-clamp technique showed that dNPA, a selective NPFF(2) agonist, increased the voltage-dependent potassium outward currents (about 30 pA/pF) by 21%; this reversible effect on sustained delayed potassium currents is blocked by tetraethylammonium. The similar effects of NPFF and opioid agonists on K(+) currents in this cell line may explain their similar antinociceptive actions at the spinal level.