Fig 1: Proposed working model of tonic GABA regulation in the ARC of Chow and HFD mice. In chronic high-fat diet (HFD) obese mice, astrocytes are turned into a reactive state and astrocytic GABA production is increased by monoamine oxidase-B (MAOB) in the arcuate nucleus (ARC) compared with chow diet (Chow) mice. However, tonic inhibition is not altered in HFD mice, and paradoxically, MAOB and GABAA-a5 (GABRA5) expression were increased in ARC. The reason for unaltered tonic inhibition in HFD mice is that GABA transporters 1 (GAT1) compensate for the increase of GABA synthesis and GABAA receptor.
Fig 2: Elevated extrasynaptic GABAA receptor in the ARC after chronic HFD feeding. (A and B) Representative traces of GABA-induced tonic current in Chow (A) and HFD (B) mice. (C) Paired plot showing Iholding/Cm (pA/pF) change in Chow and HFD mice (Chow, n=11 cells from 4 mice; HFD, n=10 cells from 4 mice). (D) Summarized bar graph showing GABA-induced tonic current density (pA/pF) in chow and HFD mice (Chow, n=11 cells; HFD, n=10 cells; Mann-Whitney test, p=0.0037). (E) Representative images of GABRA5 and NeuN immunostaining in the ARC of Chow and HFD mice (inset scale bar, 5 µm). (F) Quantification of GABRA5 intensity in Chow and HFD mice (Chow, n=129 cells from 3 mice; HFD, n=208 cells from 3 mice; Mann-Whitney test, p=0.0029). (G) Percentages of GABRA5-positive neurons in Chow and HFD mice (Chow, n=3 slices from 3 mice; HFD, 3 slices from 3 mice; Mann-Whitney test, p=0.7). Data are presented as mean ± SEM. **p<0.01.
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