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Fig. 4. Stochastic Ca2+ fluctuations in the PDCs and regular Ca2+ oscillations in the soma in DA neurons. (A) Fluorescence image of a dissociated DA neuron with cytosolic Ca2+ measuring sites. Ca2+ oscillations in the soma (S-black trace) and proximal dendritic region (P-red trace) were simultaneously measured with spontaneous firing. Right, mean amplitudes (red closed circle) and distributions of individual amplitudes (black open circle) of Ca2+ oscillations in the soma (0.051 ± 0.005 ∆F/F0, n = 31) and PDC (0.118 ± 0.007 ∆F/F0, n = 36). **p < 0.001. (B) Distribution of AUCs of Ca2+ oscillations in the soma (black) and PDCs (red). inset: Shaded zone indicates amount of Ca2+ influx from a single spike. (C) Coefficients of variation of Ca2+ oscillation AUCs in the proximal dendrite (SD = 0.04479, n = 36) and the soma (SD = 0.03015, n = 31). *p < 0.001. (D) Basal level of spontaneous Ca2+ oscillations in the soma and PDCs in spontaneous firing and silenced conditions by TTX treatment. Left, Ca2+ oscillation traces at the soma (black) and PDCs (red). Right, statistic results. Changes of Ca2+ levels in the soma and PDCs in the firing (proximal = 93.40 ± 1.04 µM, soma = 88.61 ± 1.96 µM, **p < 0.001, n = 6) and silenced conditions (TTX treatment, proximal = 76.98 ± 0.68 µM, soma = 78.95 ± 0.25 µM, p = 0.67, n = 6). (E) ISI variability during tonic firing was decreased by isradipine (50 µM, 0.27 ± 0.19, **p < 0.001, n = 8). (F) Dynamic interaction model between the soma and PDCs. Highly excitable and stochastically-fluctuating PDCs are electrically coupled with the regularly oscillating inertial soma. Values are presented as mean ± SE. PDCs, proximal dendritic compartments; DA, dopamine; AUCs, areas under the curves; TTX, tetrodotoxin; ISI, interspike interval; n.s., not significant.
Korean J Physiol Pharmacol 2024;28:165-181
© Korean J Physiol Pharmacol