Figure 6.

In vivo microdialysis after acute cocaine. The effects of cocaine (20 mg/kg, i.p.) and saline (10 μl/g, i.p.) on extracellular DA levels in the striatum of freely moving mice as measured using in vivo microdialysis. Data are presented as the percentage of the average level of dopamine measured in at least three samples collected before the drug administration. Analysis of area under curve values for 2 hr after cocaine treatment (data not shown) revealed a significant increase in DA in both genotypes compared with the saline treatment of the respective genotype (p < 0.01; two-tailed Mann-Whitney U test). No significant differences were observed between genotypes after saline (WT, n = 5; βarr2-KO, n = 5) or cocaine (WT, n = 5; KO, n = 4; p > 0.05; two-tailed Mann-Whitney U test).