ObjectiveTo observe the effect of ATP on transient outward potassium current (IA) and the underlying mechanism in the cultured trigeminal ganglion (TG) neurons by using whole-cell patch clamp technique. MethodsThe TG neurons were acutely separately from male SD rats and were cultured in vitro, and then were subjected to whole-cell patch clamp 4 h later. ResultsThe results showed that the ATP-activated currents in rat TG neurons could be classified into three types (T, S and B type). ATP significantly inhibited IA on T type neurons (P<0.05), and TNP-ATP, an antagonist of P2X3 receptors, could block the inhibitory effect of ATP against IA. ATP did not inhibit IA in S type neurons. Meanwhile, ATP could inhibit IA in TG neurons in which ATP could not induce any inward currents. Suramin, an antagonist of P2Y receptors, could block the inhibitory effect of ATP against IA . ConclusionATP can inhibit IA in cultured TG neurons, probably through P2X3 or P2Y receptors. Further studies are required to clarify the underlying mechanisms by which ATP affect IA, which will cast lights on the mechanism of neuropathic pain and provide evidence for the clinical therapy.