Data are expressed as percent of average baseline values (% mean ± s.e.m.). Mean baseline level of extracellular 5-HT was  pg/sample in the NAcc (). (a) Effect on 5-HT efflux in the NAcc of reverse dialysis infusion of WIN 55,212-2 in the DRN. The open horizontal bars indicate the 30-min period of drug infusion. WIN 55,212-2 (300 and 1000 μM) in the DRN produced a concentration-dependent increase in 5-HT efflux in the NAcc. * and ** versus vehicle examined by the repeated measures ANOVA followed by post hoc Scheffe test. (b) Effect on the WIN 55,212-2-induced increases in 5-HT efflux in the NAcc mediated by the reverse dialysis infusion of bicuculline (100 μM) in the DRN. Systemic injection of WIN 55,212-2 at 5 mg/kg i.p. took place at time zero. Bicuculline pretreatment in the DRN blocked the systemic effect of WIN 55,212-2 on 5-HT efflux in the NAcc.