Figure 3.

Calorie restriction increases glutamatergic signaling onto VTA dopamine neurons and conditioned place preference (CPP) for a food reward. A. Calorie Restriction significantly increased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; left) but not N-methyl-d-aspartate (NMDA, right) receptor current amplitude. B. Left: Calorie Restriction significantly increased the AMPA/NMDA receptor current ratio. Independent Student's t-test, ad lib n/N = 8/5, calorie restricted (CR) n/N = 8/4, ∗∗P < 0.01, ∗∗∗P < 0.001. Right: Representative voltage clamp recordings of total (black) and NMDA receptor (grey) currents at a holding potential of 40 mV. NMDA currents were recorded in the presence of the AMPA inhibitor cyanquixaline (CNQX, 10 μM). AMPA currents were obtained by subtracting NMDA from total currents. C. Mean time spent on the food reward associated side of a CPP box for ad lib fed and CR mice before (pre-test) and after (test) conditioning for the food reward. Both ad lib fed and CR mice spent more time on the food reward associated side; however, CR mice spent significantly more time than did ad lib fed mice. Repeated measures 2-way ANOVA, Sidak's multiple comparison test; interaction between diet state and conditioning (F (1, 14) = 4.815, p < 0.05). Different letters indicate that groups are statistically different from each other (P < 0.05). Data represented as mean ± SEM.