Figure 2. Effects of the GABA_B receptor antagonist CGP56433A on ICSS performance during nicotine/saline withdrawal.

Data are expressed as the percentage of baseline thresholds obtained on the last day of pump exposure before removal of the minipump (mean ± SEM). The arrowhead indicates the time-point (30 h post-pump removal) when the GABA_B receptor antagonist CGP56433A was administered. Asterisks (**P < 0.01, ***P < 0.001) indicate statistically significant elevations in ICSS thresholds in nicotine-treated groups compared with the saline/0 mg/kg CGP56433A-treated group. Plus signs (⁺P < 0.05, ⁺⁺⁺P < 0.001) indicate significant differences between each nicotine-treated group compared with its corresponding saline-treated group that received the same dose of CGP56433A and compared with the nicotine/vehicle-treated group at the 30 h time-point (Newman-Keuls post hoc test). The pound signs (^###P < 0.01) indicate a significant main effect of CGP44532 at the 30 h time-point.