The different effects of capsaicin on IA and IK currents in pain-conduct neurons of trigeminal ganglia (TG) were investigated. In cultured TG neurons of rats, whole-cell patch clamp techniques were used to record the IA and IK before and after capsaicin perfused. Results revealed that 1 μmol/L capsaicin could inhibit the amplitude of IA by 48.2% (n=10, P＜0.05), but had no inhibitory effect on IK (n=7, P＞0.05). Ten μmol/L capsaicin could significantly inhibit the amplitude of IA by 93.2% (n=8, P＜0.01), but only slightly inhibit the amplitude of IK by 13.2% (n=7,P＜0.05). Neither 1 μmol/L nor 10 μmol/L capsaicin had effects on the active curve of IA and IK.It was concluded that capsaicin could selectively inhibit the IA current, and this effect might involve in the analgesic mechanisms of capsaicin.