Figure 6.

Fasting increases the release probability of GABA from DMH terminals onto POMC neurons. A, Confocal micrograph of a sagittal hypothalamic slice demonstrating the expression of ChR2^eYFP in the dorsomedial hypothalamus and transgenically expressed Td-tomato in POMC neurons in the arcuate nucleus. B, Individual IPSCs (gray) and an average of these events (black) recorded from a POMC cell while light stimulates ChR2-expressing DMH terminals in the presence of DNQX (left). IPSCs were confirmed to be GABA_A receptor-mediated by the addition of BIC to the recording solution (right). C, Representative voltage-clamp recordings demonstrating the PPR of light-evoked IPSCs recorded from POMC neurons. ChR2-expressing DMH terminals were light stimulated, as indicated by the blue dash above the trace, at an interstimulus interval of 100 ms. Mice were fed ad libitum (top), fasted overnight (middle), or re-fed for 2 h following an overnight fast (bottom). Representative traces are the average of 10–20 consecutive traces. D, Summary data showing that an overnight fast increases the release probability of GABA from DMH neurons onto POMC cells and that a 2 h re-feed is sufficient to return release probability to that of animals that had ad libitum access to standard rodent chow (F_(2,31) = 3.970, p = 0.029, one-way ANOVA; *p = 0.032, Tukey's multiple comparison; NS = not significant, p = 0.865, Tukey's multiple comparison).