Objective  To explore whether there are abnormalities of P300like potential in stressed rats following repeatedly forced swim stress.   Methods  Forty male rats were randomly divided into 4 groups

the control groups (Control-1 and Control-2) and the stress groups (Stress-1 and Stress-2). Rats in stress groups were administered to repeatedly forced swim for 7 or 14 d respectively. Body weight gain

saccharin pre-ference test and open field test were performed. After being anesthetized with urethane

P300-like potential were evoked by the oddball auditory stimulation. Deviant sounds were presented in a homogenous series of standard sounds.   Results  Our results of behavioral tests displayed less body weights and less saccharine solution intake in stressed group rats and significant effects of stress on the number of crossing squares

the duration of rearing and the number of grooming in open field test. Prolonged P3 latencies and decreased P3 amplitudes of P300-like potentials were found in the stressed rats. Moreover

there were significant correlations between parameters of P300 (including P3 latency and P3 amplitude) and a serial of behavioral traits.   Conclusion  This study provides an important evidence of changes of P300-like potential in depressed rats following repeatedly forced swim stress. Based on this study

event related potentials should be taken into consideration and applied as the useful tools in the research work of depressed animal models.