Figure 1: Acute HFD modulates the neurochemical phenotype of brainstem astrocytes.

A. A schematic diagram illustrating the experimental timeline. Rats (N=5–8 per time point) were exposed to a HFD for 1, 3, 5, and 14d prior to tissue fixation and processing for immunohistochemical localization of GFAP-immunoreactivity (-IR; green; labelling activated astrocytes) or ChAT-IR (magenta; labelling cholinergic neurons). Brainstems were harvested from rats on a control diet at each time point at the same time as the HFD samples (N=6–8 per time point). B. Representative higher magnification images of the DVC in control (upper) and following 3d of acute HFD exposure (lower) illustrating GFAP (left) and GFAP+ChAT co-localization (right). Scale bar = 50μm. C. Graphical representation of GFAP-IR in the left and right DMV of control and HFD rats at 1, 3, 5, and 14d of HFD exposure. In the HFD group, GFAP mean fluorescence intensity was significantly increased at 3 and 5d compared to 1 or 14d. In addition, there was a significant difference in GFAP mean fluorescence intensity between control and HFD rats at day 3 and day 5 (multivariate ANOVA with targeted contrasts: *p<0.05, one-way ANOVA with post-hoc Bonferroni multiple comparison test, N=5–8 per time point. Data are represented as mean±SD). D. Graphical representation of GFAP-IR in the left and right NTS of control and HFD rats at 1, 3, 5, and 14d of HFD exposure. (*p<0.05, one way ANOVA with post-hoc Bonferroni multiple comparison test). E. Representative images of GFAP and GFAP+ChAT (left and right image in each set, respectively) DVC in control (left) and time matched HFD (right) rats at 1, 3, and 14d (top to bottom, respectively). Images were taken at the same confocal settings for comparison between groups. White scale bar = 150μm.

AP = area postrema, CC = central canal, NTS = nucleus tractus solitarius, DMV = dorsal motor nucleus of the vagus