Nicotine-elicited DA release in the ventral striatum of α6-/- mice. A-C, Mice (n = 4-7 animals per group) were injected intraperitoneally with a solution of 0.5 or 1 mg kg^-1 nicotine (free base), and extracellular DA levels were measured by microdialysis in the ventral striatum. Results are expressed as percentage of basal DA levels (mean of 5-8 samples collected immediately before treatment). Basal DA levels in perfusate did not differ between the two genotypes. D, AUC values, representing the amount of DA outflow collected during the 0-120 min post-treatment period, are expressed as percentage of basal values. (^*p < 0.05 and ^**p < 0.01 relative to the corresponding control NaCl-treated group; two-way ANOVA). No statistically significant difference between α6+/+ and α6-/- mice is observed.