Facilitation of ICSS in rats by S(+)MDPV (0.032–1.0 mg/kg; n = 6) but not by R(−)MDPV (0.32–10 mg/kg; n = 5). (A) The abscissa shows drug dose in mg/kg (log scale; VEH = vehicle), and the ordinate shows rates of ICSS expressed as the percentage of the baseline number of stimulations delivered per component across all brain stimulation frequencies. The asterisk indicates significantly different from VEH, as determined by one-way ANOVA followed by a Dunnett’s posthoc test (p < 0.05). (B, C) The abscissa shows brain stimulation frequency in log Hz, and the ordinate shows rates of ICSS expressed as the percent of the maximum control rate (%MCR), a normalized measure of ICSS reinforcement rate. Filled points indicate significantly different from VEH, as determined by two-way ANOVA followed by the Holm–Sidak posthoc test (p < 0.05).