Fig. 3: Midbrain dopamine in the hippocampus contributes in learning a new context in DAT::Cre mice. | Nature Communications

Fig. 3: Midbrain dopamine in the hippocampus contributes in learning a new context in DAT::Cre mice.

From: Ventral tegmental area dopamine projections to the hippocampus trigger long-term potentiation and contextual learning

Fig. 3

a Schema illustrating the behavioral procedure. DAT::Cre mice were used in a context pre-exposure facilitation effect paradigm. First, the effect of different pre-exposure durations was studied, and then the effect of optogenetic manipulation of midbrain dopamine afferents to the hippocampus was evaluated. On day 2, mice received an immediate shock, and on day 3 freezing was tested in the conditioned context and in an alternative one. b Preexposure had a significant effect on freezing to the conditioned context (ANOVA, p = 0.0008) in DAT::Cre mice. Animals pre-exposed for 30 seconds (n = 9 mice) did not freeze more than control non-pre-exposed group (n = 8 mice, Tukey post hoc test: p = 0,78). 2 min pre-exposure was sufficient to induce a significant increase (n = 9 mice, Tukey post hoc test: p = .0024) reaching levels comparable to those seen in the group with 8 min pre-exposure (n = 8 mice, Tukey post hoc test: p = 0.0041). c Mice were pre-exposed for 30 seconds on day one during which they received 90 bursts of blue light bilaterally in the dorsal hippocampus. Freezing in the conditioned context increased in the ChETA-injected mice (blue, n = 19 mice) compared the YFP-injected mice (orange, n = 16 mice, t-test: p = 0.0016). Freezing in the alternative context was considerably lower than in the conditioned context and was not significantly changed due to dopaminergic activation during pre-exposure (t-test: p = 0.23). d Mice were pre-exposed for 2 minutes on day one during which they received continuous green light. Freezing in the conditioned context levels observed during the test on day 3 were lower for eNpHR3.0 injected mice (green, n = 11 mice) in comparison to mice with control injection (orange, n = 7 mice, t-test: p = 0.0021). Freezing in the alternative context was considerably lower than in the conditioned context and was not significantly changed due to dopaminergic inhibition during pre-exposure (t-test: p = 0.60). Data are presented as mean values +/- SEM. Sample size (n) indicates the number of mice included for each experimental group. ## p < 0.01 Multiple comparisons following one-way ANOVA (p < 0.001). ** p < 0.01 t-test. All statistical tests were two-sided. Illustrations include an image created with BioRender.com. Source data are provided as a Source Data file.

Back to article page