Time course of the effect of dorsal raphe nucleus (DRN) electrical stimulation at 3, 5, 10, and 20 Hz on DA, DOPAC, and 5-HIAA extracellular levels in the rat nucleus accumbens (NAC) and striatum. Each data pointrepresents the mean percentage ± SEM of baseline values calculated from three samples before DRN stimulation, performed for a 15 min period as indicated by the horizontal bar. Each experiment was performed on five or six animals per group. *p < 0.05 and **p < 0.01 as compared with the sham-stimulated group (unfilled circles) for each time point (Dunnett’s test).