Figure 7.

VTA GLP-1R stimulation in overnight ad libitum-fed rats is sufficient to suppress food intake and reward behavior. The effects of microinjection of EX4 into the VTA on chow intake and PR operant conditioning for sucrose in satiated rats were tested. A, The number of sucrose pellets earned in the PR operant test was significantly decreased by EX4 VTA microinjection. B, Number of rewards earned by the satiated animals analyzed by dividing them into those with a high motivation to work for sucrose at their satiated baseline (on the vehicle condition earned 6 or more rewards; n = 6) and those displaying a low motivation for sucrose (on vehicle earned 5 or less rewards; n = 8). These data might indicate an enhanced sensitivity to the reward reducing effects of EX4 in high reward responders, i.e., those rats are highly motivated to earn sucrose despite their satiated state. C, D, VTA microinjection of EX4 reduced free-feeding on chow at both the 1 h and the 24 h time points. *p < 0.05, **p < 0.005 comparing vehicle to each EX4 dose using the Tukey test after detecting a significant main effect of one-way ANOVA for each time point; n = 14. Data represent mean ± SEM.