The anti-depression effect of NS on the durations of immobility in the forced swim test. NS or saline was intraperitoneally injected before 24 h, 5 h and 1 h of the forced swim test, rats (n = 5 in each group) were individually placed in a glass cylinder containing water. During the 5 min test, the duration of immobility was observed and measured. The immobility time was regarded as the time spent by the mouse floating in the water without struggling. *P < 0.05 compared to control.