Fig. 4.
STN manipulations have preventive effects on cocaine escalation. a Summary time graph presenting the effect of STN lesion on the total cocaine intake throughout the 5 last ShA and 20 LgA sessions. While STN lesion has no effect on ShA, it reduces the development of cocaine escalation (ShA: group effect: F1,56 = 0.5683, n.s., LgA: session effect: F19,266 = 5.231, P < 0.0001; group effect, F1,266 = 8.939, P < 0.01, mixed two-way ANOVA; sham group, n = 10, white dots; STN lesion group, n = 6, blue dots). b Summary bar graph showing that STN lesion also reduces the cocaine intake during the first 2 h of each session averaged per blocks of five ShA (block 1) and LgA (blocks 2–5) sessions (block × group interaction: F4,56 = 4.329, P < 0.01, mixed two-way ANOVA). c Summary time graph showing the effect of STN–HFS applied during 15 LgA sessions on the total cocaine intake (OFF group: n = 11, white dots; ON group: n = 7, red dots). While both groups exhibit comparable intake during ShA, STN–HFS blocks the development of cocaine escalation (ShA: group effect: F1,64 = 0.01819, n.s.; LgA: session effect: F14,224 = 1.863, P < 0.05; group effect, F1,224 = 13.51, P < 0.01, mixed two-way ANOVA). d Summary bar graph of averaged cocaine intake during the first 2 h of each session per blocks of five ShA (block 1) and LgA (blocks 2–4) also shows that STN–HFS also blocks cocaine escalation development (block × group interaction: F3,48 = 3.081, P < 0.05, mixed two-way ANOVA). All data are means with SEM. *P < 0.05, **P < 0.01, ***P < 0.001 vs. ShA (block 1); #P < 0.05, ##P < 0.01 vs. sham group or OFF group (Bonferroni post hoc test)