Bidirectional selective breeding results for methamphetamine (MA) consumption. Selection was based on amount of MA consumed when it was offered as a 40 mg/L concentration vs. water. (a) Amount of MA consumed (mg/kg) from the 40 mg/L concentration by the founding population of C57BL/6J x DBA/2J F2 mice (F2; S0), and the MA high drinking (MAHDR) and MA low drinking (MALDR) selected line parent and offspring mice over the course of selection. (b) Amount of MA consumed from the 20 mg/L MA concentration for the same mice. (c) Preference for the 40 mg/L MA concentration (mL of MA consumed/total mL fluid consumed). (d) Total volume consumed from the MA and water tubes (mL), during the time when 40 mg/L MA was offered. Shown are means ± SEM for the average of the second and fourth day of access to the drinking solutions for this third replicate set of MA drinking selected lines. N = 120 for the F2 mice, 56–64/line/generation for the MAHDR and MALDR offspring, and 26/line/generation for their parents. *** p < 0.001 for the difference between the MAHDR and MALDR offspring; # p < 0.05, ## p < 0.01, ### p < 0.001 for the difference from the F2.