Calbindin controls release probability in ventral tegmental area dopamine neurons - PubMed (original) (raw)

Calbindin controls release probability in ventral tegmental area dopamine neurons

Ping-Yue Pan et al. Nat Neurosci. 2012 Jun.

Abstract

Relatively little is known about the molecular control of midbrain dopamine release. Using high-fidelity imaging of pHluorin-tagged vesicular monoamine transporter 2 in dopamine neurons, we found that exocytosis was more loosely coupled to calcium entry than in fast synapses. In ventral tegmental area neurons, this allows exocytosis to be efficiently controlled by a native fast calcium buffer, calbindin-D28k, maintaining a lower vesicular release probability compared with substantia nigra neurons.

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Figures

Figure 1. Synaptic vesicles are loosely coupled to calcium entry in DA neurons

(a) Difference (ΔF) images of vMAT-pHluorin responses in DA neuron boutons to a single AP stimulus (left) and NH4Cl perfusion (right), scale bar: 5 μm. (b) Average vMAT-pHluorin and vGlut-pHluorin responses to a single AP stimuli before and after EGTA-AM treatment (n = 4 trials), scale bar: 400 ms. (c) Single AP ΔF Fluo5F responses of VAMP-mCherry expressing DA and hippocampal boutons (upper, Scale bar: 400 ms) and their corresponding kinetics ( lower panels scale bar: 100 ms) before and after EGTA-AM treatment. (d) EGTA treatment preferentially suppressed phluorin responses in DA terminals (68 ± 6 %) compared to HP terminals (38 ± 5%) (p = 0.004) for similar suppression of calcium signals (p = 0.74), (56% ± 6 suppression in DA; 54% ± 4 suppression in HP).

Figure 2. Endogenous CB regulates Pv in DA neurons

(a) Midbrain neurons were stained for CB and Tyrosine hydroxylase (TH). Numbers with arrows indicate the relative expression level of CB (methods), scale bar: 10 μm. (b) Box-whisker plot (methods) showing the distribution of CB expression in 70 (from 2 preparations) TH positive cells. (c) Cross section showing VTA-enrichment ventral midbrain dissection procedure. (d) Cumulative distribution of relative CB levels in DA cells from VTA and mixed cultures. (e, f) Pv (e) and RRP (f) values binned across CB expression level. Pv values were significantly different between 1st and 3rd (p = 0.007) and 4th (p = 0.03) bin. (g, h) Comparison of Pv (g) and RRP (h) in neurons from mixed and VTA culture. Pv was significantly lower (p = 0.008) in VTA neurons.

Figure 3. CB knockdown in VTA DA neurons enhanced Pv and synaptic depression during AP bursts

(a) Single AP responses are significantly higher and lower in CB KD and overexpression compared to control, 3-way ANOVA: p < 0.0001. Inset, representative 1 AP responses for each condition, scale: 0.5% TP, 50 ms. (b, c) Pv (b) and RRP (c) measured from control, CB KD and CB KD with rescue neurons plotted against relative expression of CB. (d) Amount of exocytosis relative to the 1st AP response plotted against AP number (straight line shows zero depression) in CB KD DA and control DA neurons.

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Calbindin controls release probability in ventral tegmental area dopamine neurons - PubMed (original) (raw)