Modulation of bradykinin (BK) on ATP-activated membrane currents in the isolated rat dorsal root ganglion (DRG) neurons was investigated using whole-cell patch-clamp technique. In 56 neurons examined, BK (10(-6)-10(-4) mol/L)-induced responses were as follows: (1) inward current (40/56); (2) outward current (7/56); (3) no responses (9/56). In the majority of the neurons examined, ATP (10(-6)-10(-3) mol/L) activated a concentration-dependent inward current with obvious desensitization. ATP-activated current was potentiated markedly by preapplication of BK. The enhancement of BK was dependent on the concentration of BK and ATP. It was found that BK potentiated the peak value of ATP-activated currents predominately while the steady state value was not affected obviously. The onset of BK potentiation of ATP-activated currents needed preincubation of BK at least for 30 s and the time of the enhancement lasted over 20 min. The results suggest that BK may play a role in the facilitation of the excitatory effect of ATP on primary sensory neurons.