Fig. 1: Chronic Ethanol Exposure Dynamically Reshapes VTA DA Neuron Activity in Vivo. | Molecular Psychiatry

Fig. 1: Chronic Ethanol Exposure Dynamically Reshapes VTA DA Neuron Activity in Vivo.

From: BDNF restores impaired long-term potentiation of GABAergic synapses induced by chronic ethanol exposure in the VTA and attenuates reward-seeking behavior

Fig. 1: Chronic Ethanol Exposure Dynamically Reshapes VTA DA Neuron Activity in Vivo.

(A) Schematic of the intermittent access two-bottle choice (IA2BC) paradigm. (B) Escalating 24 h ethanol intake across 21 days of IA2BC. Ethanol intake increased from 3.66 ± 0.25 g/kg/24 h on day 1 to 19.78 ± 1.04 g/kg/24 h by day 21 (n = 24 mice). (C) Ethanol preference during IA2BC. The average preference over the 21-day period was 68.17 ± 3.79% (n = 24 mice). (D) Total 24 h fluid intake (mL) of IA2BC and water-only control mice. There was no significant difference between groups (Two-way ANOVA, F(1, 28) = 0.002, p > 0.05; n = 10 control mice, n = 24 IA2BC mice). (E) Body weight of IA2BC and water-only control mice. There was no significant difference between groups (Two-way ANOVA, F(1, 28) = 0.28, p > 0.05; n = 10 control mice, n = 24 IA2BC mice). (F) Schematic of AAV injection for GCaMP7f expression in VTA DA neurons (left). Coronal VTA section showing immunofluorescence for TH (red, DA neurons), expressed GCaMP7f reporter (dTomato, gray), and DAPI (blue). Scale bar, 100 µm. (G) Schematic of in vivo fiber photometry recording in homecage. Licking events for water or ethanol were detected by lickometers. (H-K) Representative average calcium transients (ΔF/F) aligned to licking onset (dashed line at 0 s) for ethanol (red) and water (blue) from a single mouse on Day 1 (H), Day 3 (I), Day 7 (J), and Day 21 (K). Traces represent mean ± SEM of all trials from one representative animal per time point. (L) Population heatmaps of ΔF/F responses (aligned to lick onset, dashed line) for all recorded mice. Left: Ethanol licking events. Right: Water licking events. Each row represents the average response of one mouse (n = 8 mice per time point). (M) Quantification of peak ΔF/F for ethanol (red) and water (blue) events across the four time points. Two-way ANOVA revealed significant main effects of Day (F (3, 42) = 15.62, p < 0.0001) and Fluid (Ethanol vs. Water) (F (1, 14) = 127.1, p < 0.0001), with a significant interaction (F (3, 42) = 12.90, p < 0.0001). Post hoc comparisons (Tukey’s test for across-day ethanol; Bonferroni’s test for within-day fluid): Ethanol: Day 1 (3.32 ± 0.23%) vs. Day 3 (4.82 ± 0.22%), p < 0.0001; Day 1 vs. Day 7 (4.36 ± 0.23%), p = 0.0027; Day 1 vs. Day 21 (5.80 ± 0.27%), p < 0.0001; Day 3 vs. Day 21, p = 0.0047; Day 7 vs. Day 21, p < 0.0001. Within-day Ethanol vs. Water: Day 1 (Water: 2.56 ± 0.18%), p = 0.0426; Day 3 (Water: 2.72 ± 0.19%), p < 0.0001; Day 7 (Water: 2.76 ± 0.15%), p < 0.0001; Day 21 (Water: 2.69 ± 0.15%), p < 0.0001. Water responses did not differ across days. (N) Quantification of area under the curve (AUC, %·s) for ethanol (red) and water (blue) events. Two-way ANOVA revealed significant main effects of Day (F (2.80, 39.16) = 16.70, p < 0.0001) and Fluid (F (1, 14) = 172.0, p < 0.0001), with a significant interaction (F (3, 42) = 14.21, p < 0.0001). Post hoc comparisons (Tukey’s test for across-day ethanol; Bonferroni’s test for within-day fluid): Ethanol: Day 1 (6.78 ± 0.53%·s) vs. Day 3 (10.42 ± 0.58%·s), p = 0.0058; Day 1 vs. Day 7 (9.86 ± 0.64%·s), p = 0.0168; Day 1 vs. Day 21 (13.26 ± 0.68%·s), p = 0.0002; Day 7 vs. Day 21, p = 0.0187. Within-day Ethanol vs. Water: Day 1 (Water: 4.35 ± 0.41%·s), p = 0.0122; Day 3 (Water: 4.47 ± 0.42%·s), p < 0.0001; Day 7 (Water: 4.79 ± 0.33%·s), p = 0.0001; Day 21 (Water: 4.64 ± 0.37%·s), p < 0.0001. Water responses did not differ across days. All bar/box plots in (M, N) show data from n = 8 mice per time point. Data are presented as mean ± SEM. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

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