Figure 2. POMCARH neurons directly inhibit a portion of DAVTA neurons via MOR-mediated mechanisms.
(A) Recordings in POMCARH-innervated DAVTA neurons [GFP(+)TOMATO(+)] in response to photostimulation of ChR2-labelled POMCARH-originated fibers within the VTA. (B) Representative traces for light-evoked EPSC, which were blocked by 30 μM D-AP5 and 30 μM CNQX, but not affected by 400 μM 4-AP and 1 μM TTX. (C) The percentage of GFP(+)TOMATO(+) neurons that showed light-evoked EPSCs or no response. (D) The percentage of GFP(+)TOMATO(+) neurons that showed light-evoked IPSCs or no response. (E-I) Representative action potential traces in GFP(+)TOMATO(+) neurons in response to photostimulation of POMCARH-originated fibers within the VTA, in the absence (E) or presence of SHU9119 (50 μM, F), naltrindole (100 μM, G), norbinaltorphimine (100 μM, H), or cyprodime (200 μM, I). (J-K) Light-induced changes in firing frequency (J) and resting membrane potential (K). Results are shown as mean ± SEM. **, P<0.01 and ***, P<0.001 between cyprodime group vs. no blockers in one-way ANOVA analyses followed by Sidak post hoc test (N=10–19 neurons from 3 mice per group). (L) Relative mRNA levels of MC3R, MC4R and MOR in single VTA neurons labelled by both GFP and TOMATO. Results are shown as mean ± SEM with each data point plotted. N=4 neurons from 2 mice per group.