Figure 1.

Active lever responses across repeated cycles of self-administration, extinction, and reinstatement testing in male Sprague-Dawley rats that self-administered MDPV (upper panel; n=18–20) or a mixture of MDPV+caffeine (lower panel; n=15–20). Abscissa: the last 3 days of self-administration, the first 7 days of extinction, and the CS test (saline pretreatment) Ordinate: total responses on the active lever during the 90-min session. Data represent the mean (± 1 S.E.M.) for 5 cycles of the procedure.