Supplementary Figure 5: Systemic SYN119 does not inhibit the expression of incubation of sucrose seeking.

As shown in the experimental timeline (a), rats underwent 10 days of sucrose self-administration (SA) (6 h/day). During these sessions, presses on the active lever resulted in delivery of sucrose solution into a liquid drop receptacle (10% sucrose solution, 0.75 ml per reward delivery) paired with a cue-light and tone presentation (20 sec). As shown in (b), no difference in sucrose deliveries during the 10 days of self-administration was observed between rats destined for acute vehicle or SYN119 (SYN) treatment groups. Data shown are the mean (± s.e.m.) number of infusions obtained during each 6 h session. (c) Rats in both groups then underwent withdrawal in their home cages and were tested twice for cue-induced sucrose seeking. In these tests (30 min), active lever presses resulted in the presentation of the cue-light and tone, but no sucrose delivery. The first test was on withdrawal day (WD) 1 and the second test was on WD30, 20 minutes after an acute injection of vehicle or SYN (10 mg/kg, i.p., dissolved in 10% Tween-80). Rats in both groups showed a significant increase in cue-induced sucrose seeking (i.e., incubation) from WD1 to WD30, indicating that systemic SYN administration has no effect of incubation of cue-induced sucrose craving. The ANOVA revealed no significant group effect or group X day interaction, but a significant effect of test day (F_1,21=24.43, p<0.001). Post-hoc least significant difference tests revealed a significant increase in active lever responses on WD30 compared to WD1 in both groups and no difference between groups on either test day. Data shown are the mean number of responses (± s.e.m.) on the active lever during the two tests for cue-induced sucrose seeking. *p<0.05, WD30 versus WD1 (p=0.002, Vehicle WD30 versus WD1; p=0.007, SYN119 WD30 versus WD1); Vehicle, n=11 rats; SYN119, n=12 rats.