Time course of the effect of 20 Hz dorsal raphe nucleus (DRN) electrical stimulation on DA and DOPAC extracellular levels in the nucleus accumbens (NAC) and the striatum in saline-treated (unfilled circles) andpara-chlorophenylalanine-treated (pCPA, filled squares) rats. Eachdata point represents the mean percentage ± SEM of baseline values calculated from three samples before DRN electrical stimulation, performed for a 15 min period as indicated by thehorizontal bar. Each experiment was performed on five or six animals per group 24 hr after the last injection of saline or pCPA. In both the NAC and the striatum, pCPA treatment reduced the overall effect of DRN stimulation on DA, but not on DOPAC, extracellular levels (see Results). *p < 0.05 and **p < 0.01 as compared with the saline group for each time point (Student’s t test).