[P2-3-12] Distinct dopamine dynamics in the dorsal and ventral striatum during saccharin water intake
Keywords:ドーパミン、線条体、ファイバーフォトメトリー
The striatum is a major cortical input site of the basal ganglia and is divided into a dorsal and a ventral part. The dorsal striatum (DS) and the ventral striatum (VS) contribute to different cognitive functions, such as goal-directed behaviors and motivation, respectively. Many lines of research have demonstrated that dopamine plays a critical role in acquisition of these functions (e.g. Yoshizawa et al., bioRxiv, 2023). Anatomically, the substantia nigra pars compacta contains mostly DS-projecting dopaminergic neurons, whereas the ventral tegmental area contains mostly VS-projecting dopaminergic neurons, therefore it is possible that dopamine release in the DS and VS has different dynamics. In the present study, we measured dopamine release in the DS and VS when mice drank saccharin water in order to examine the reward information conveyed to the DS and VS. A fiber photometry recording was applied to mice expressing dopamine sensor dLight1.1 in the DS (N=6 mice) or VS (N=5 mice) while they performed an operant conditioning task under head fixation. Each trial began with turning on a house lamp. When the mouse spontaneously licked the water spout (without any cue signal), two drops of 0.1% saccharin water (2 μl, 2 times for 0.2 s) was or was not presented immediately with equal probability. The fluorescent signal of dLight1.1 showed significantly shorter peak time from reward (median, DS: 0.49 s, VS: 0.90 s, p=0.043, Mann-Whitney U test) and decay time from peak (median, DS: 0.30 s, VS: 0.75 s, p=0.026) in the DS than in the VS. In the DS, phasic dopamine release was observed with each drop of saccharin water, resulting in bimodal release dynamics. In VS, a unimodal release dynamics was observed with phasic dopamine release induced by intake of the first drop of saccharin water, followed by weighted dopamine release by intake of the second drop. These results suggest that the DS receives information about reward frequency, whereas that the VS receives information about reward volume.