Figure 4.

Orexin mediates the effect of caloric restriction on glutamate currents on VTA dopamine neurons. A. There were no significant differences in AMPA or NMDA receptor current amplitude on VTA dopamine neurons from calorie restricted (CR) mice injected with control (pAAV-hSyn-DIO-mCherry) or inhibitory (pAAV-hSyn-DIO-hM4D(Gi)-mCherry) virus and given C21 (10 mg/kg) or vehicle (distilled water) in their drinking water (Two-way ANOVA followed by Tukey's post-hoc test, P > 0.05). B. The AMPA/NMDA receptor current ratio was significantly reduced in CR mice injected with the inhibitory DREADD and provided C21. Different letters indicate that groups are statistically different from each other (P < 0.05) (Two-way ANOVA followed by Tukey's post-hoc test, interaction between AAV and treatment ((F (1, 29) = 6.023, p < 0.05). Control-vehicle n/N = 8/4, control-C21 n/N = 9/5, Inhibitory DREADD-vehicle n/N = 8/5, Inhibitory DREADD-C21 n/N = 8/4. C. 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. D. AMPA/NMDA receptor current ratio in VTA dopamine neurons from CR mice injected with the inhibitory DREADD and provided C21 in their drinking water in the presence (C21+, n/N = 8/4) or absence (C21-, n/N = 9/4) of C21 in the recording bath. There were no significant differences between the groups (Independent Student's t-test). Data represent mean ± SEM.