Figure 5: Inhibition of presynaptic AMPK activity reduces mIPSC frequency.

(a,b) Sample recording traces showing mIPSCs recorded from POMC neurons with the AMPK inhibitor dorsomorphin (a) and the AMPK activator A769662 (b). The AMPK inhibitor significantly decreased GABA release at 2.5 mM glucose (a), whereas the AMPK activator robustly increased mIPSC frequency at 10 mM glucose (b). The results suggest that presynaptic AMPK plays a major role in regulating GABA release. HP=−70 mV. Scale bar, 100 pA, 10 s. (c) Summary plot showing AMPK modulators’ effect on mIPSC frequency (dorsomorphin: n=6 neurons; A769662: n=7 neurons). C, control. (d,e) Representative recording samples showing leptin’s effect on mIPSCs recorded from POMC neurons in the presence of the AMPK inhibitor dorsomorphin and the PI3K inhibitor wortmannin at 5 mM glucose. Leptin increased mIPSC frequency in the presence of the AMPK inhibitor. The PI3K inhibitor completely abolished leptin’s action on mIPSCs. HP=−70 mV. Scale bar, 100 pA, 10 s. (f) Summary plot showing leptin’s effect on mIPSC frequency in the presence of the AMPK inhibitor and the PI3K inhibitor. As leptin no longer modulates mIPSCs in the presence of the PI3K inhibitor, both pre- and postsynaptic PI3K signalling is a key factor for leptin’s effect. However, presynaptic AMPK is involved in leptin-mediated reduction of GABA release (dorsomorphin: n=9 neurons; wortmannin: n=10 neurons). *P<0.05, **P<0.01 versus control (paired t-test). All data are shown as mean±s.e.m.