Abstract: Objective To explore the changes of the painful P300 under the state of pain induced by adjuvant induced arthritis (AIA) inrabbits. Methods The painful P300 and pain threshold in 10 rabbits were recorded before Freud's adjuvant injection, before and after morphineinjection on the 7th day and the 21st day after Freud's adjuvant injection. Results With the pain threshold lowed (P<0.01), the latencyof painful P300 was differentially shortened on the 7th day and 21st days after adjuvant injection (P<0.01). After morphine injected, painthreshold increased (P<0.01) and the latency of painful P300 was prolonged (P<0.01). On the 7th day, the amplitude of painful P300 differentiallyincreased (P<0.05), and decreased (P<0.01) after morphine injected. The amplitude of painful P300 on the 21st day was significantlylower than that of the 7th day (P<0.01). The pain threshold correlated with the latency of painful P300 (r=0.516, P<0.01). ConclusionPainful P300 is related with the condition of pain in rabbits with AIA.

Key words: adjuvant induced arthritis, P300, pain evoked potentials, amplitude, latency, pain threshold