Fig. 2.

Effects of repeated cocaine or saline treatment on cocaine-induced increases in extracellular levels of dopamine (DA) and glutamate (GLU) in the NAc of adolescent and adult mice. (A, left panel) Cocaine-pretreated adult mice (Adult-Coc, n=10) displayed greater peak extracellular DA levels in the NAc as compared to cocaine-pretreated adolescent mice (Adol-Coc, n=11) at 30 min post cocaine injection (*,p<0.05). In addition, cocaine-induced increases in extracellular DA in Adult-Coc were higher throughout the post-injection period as compared with Adol-Coc mice (+,p<0.05). Peak cocaine-induced increases in dialysate DA content were observed within 15 min of injection in Adol-Coc and saline-pretreated adolescent mice (Adol-Sal, n=10). In contrast, peak cocaine-induced increases in dialysate DA content were observed within 30 min of injection in Adult-Coc and saline-pretreated adult mice (Adult-Sal, n=7) (#, p<0.05). (B, right panel) Area-under-the-curve (AUC) analysis revealed that cocaine-pretreated mice displayed greater overall increase in extracellular DA during the 2 hr post-injection period as compared with saline-pretreated mice (*, p<0.05). (C, left panel) Saline-treated Adult mice (n=7) displayed greater peak increases in extracellular Glu levels in the NAc as compared to saline-treated Adol mice (n=7) at 15 min post-injection (*, p<0.05). (D, right panel) (p>0.05). No differences in peak dialysate levels of Glu or AUC were observed between Adol-Coc (n=9) and Adult-Coc (n=7). For all panels, first four microdialysis samples represent baseline samples. Data are presented as mean ± SEM.