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Dominance of P/Q-type calcium channels in depolarization-induced presynaptic FM dye release in cultured hippocampal neurons.

Nimmervoll B, Flucher BE, Obermair GJ - Neuroscience (2013)

Bottom Line: Analysis of the release kinetics and the fractional release amplitude demonstrate that, whereas in only 15% of the synapses release depended exclusively on P/Q-type channels, the majority of synapses (85%) contained both N- and P/Q-type channels.Nevertheless, the kinetics of FM dye release in synapses containing both channel types was determined by the P/Q-type channels.Together, our data suggest a more direct coupling of P/Q-type channels to synaptic release compared to N-type channels, which may explain the high prevalence of neurological P/Q-type channelopathies.

View Article: PubMed Central - PubMed

Affiliation: Division of Physiology, Medical University Innsbruck, Fritz-Pregl-Str. 3, 6020 Innsbruck, Austria.

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Dissecting the contribution of presynaptic Ca2+ channels to depolarization-induced FM dye release. Frequency distribution histograms of the Rf values of all synapses normalized to the mean of the control condition after pharmacological block of presynaptic Ca2+ channels. (A) Combined CTx and Aga application (orange) compared to control (blue). (B–D) For a better comparison of the CTx-only (red) and Aga-only (green) treatments the traces of the CTx–Aga and control treatments are displayed as light and dark gray shaded areas, respectively. See text for description. Number of synapses (experiments) analyzed: control, 707 (18); CTx, 556 (14); Aga, 474 (12); CTx + Aga, 398 (10) from 3 to 4 separate culture preparations.
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f0020: Dissecting the contribution of presynaptic Ca2+ channels to depolarization-induced FM dye release. Frequency distribution histograms of the Rf values of all synapses normalized to the mean of the control condition after pharmacological block of presynaptic Ca2+ channels. (A) Combined CTx and Aga application (orange) compared to control (blue). (B–D) For a better comparison of the CTx-only (red) and Aga-only (green) treatments the traces of the CTx–Aga and control treatments are displayed as light and dark gray shaded areas, respectively. See text for description. Number of synapses (experiments) analyzed: control, 707 (18); CTx, 556 (14); Aga, 474 (12); CTx + Aga, 398 (10) from 3 to 4 separate culture preparations.

Mentions: In order to characterize the channel-type composition of individual synapses we generated frequency distribution histograms of Rf values of all individual recorded synapses in the different conditions (Fig. 4) normalized to the mean of the control. The Rf values of the control synapses show a wide normal distribution around the mean of 1.00 ± 0.33 (mean ± SD; Fig. 4A, blue line). In stark contrast, the distribution of the combined CTx and Aga block (Rf 0.29 ± 0.23; mean ± SD; Fig. 4A, orange line) displays a prominent peak at an Rf of approximately 0.2 – representing synapses with maximally blocked release – followed by a smaller population of synapses showing severely reduced release. Cluster analysis revealed that 75% of the synapses fall within this maximally blocked population (Rf 0.18 ± 0.10; mean ± SD; Fig. 4C, light orange area), indicating that release depended on presynaptic N- and P/Q-type channels. The tail of the skewed distribution represents the remaining 25% responding synapses, albeit at a strongly reduced efficacy. Comparing CTx-treated synapses with the control and combined CTx + Aga groups (Fig. 4B) reveals that the distribution of Rf values of CTx blocked synapses (red) is indistinguishable from the control condition (Rf 0.99 ± 0.32; mean ± SD). Thus blocking only N-type channels did neither affect the release properties of the entire synapse population, nor reveal a subpopulation of synapses entirely depended on N-type channels.


Dominance of P/Q-type calcium channels in depolarization-induced presynaptic FM dye release in cultured hippocampal neurons.

Nimmervoll B, Flucher BE, Obermair GJ - Neuroscience (2013)

Dissecting the contribution of presynaptic Ca2+ channels to depolarization-induced FM dye release. Frequency distribution histograms of the Rf values of all synapses normalized to the mean of the control condition after pharmacological block of presynaptic Ca2+ channels. (A) Combined CTx and Aga application (orange) compared to control (blue). (B–D) For a better comparison of the CTx-only (red) and Aga-only (green) treatments the traces of the CTx–Aga and control treatments are displayed as light and dark gray shaded areas, respectively. See text for description. Number of synapses (experiments) analyzed: control, 707 (18); CTx, 556 (14); Aga, 474 (12); CTx + Aga, 398 (10) from 3 to 4 separate culture preparations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3824072&req=5

f0020: Dissecting the contribution of presynaptic Ca2+ channels to depolarization-induced FM dye release. Frequency distribution histograms of the Rf values of all synapses normalized to the mean of the control condition after pharmacological block of presynaptic Ca2+ channels. (A) Combined CTx and Aga application (orange) compared to control (blue). (B–D) For a better comparison of the CTx-only (red) and Aga-only (green) treatments the traces of the CTx–Aga and control treatments are displayed as light and dark gray shaded areas, respectively. See text for description. Number of synapses (experiments) analyzed: control, 707 (18); CTx, 556 (14); Aga, 474 (12); CTx + Aga, 398 (10) from 3 to 4 separate culture preparations.
Mentions: In order to characterize the channel-type composition of individual synapses we generated frequency distribution histograms of Rf values of all individual recorded synapses in the different conditions (Fig. 4) normalized to the mean of the control. The Rf values of the control synapses show a wide normal distribution around the mean of 1.00 ± 0.33 (mean ± SD; Fig. 4A, blue line). In stark contrast, the distribution of the combined CTx and Aga block (Rf 0.29 ± 0.23; mean ± SD; Fig. 4A, orange line) displays a prominent peak at an Rf of approximately 0.2 – representing synapses with maximally blocked release – followed by a smaller population of synapses showing severely reduced release. Cluster analysis revealed that 75% of the synapses fall within this maximally blocked population (Rf 0.18 ± 0.10; mean ± SD; Fig. 4C, light orange area), indicating that release depended on presynaptic N- and P/Q-type channels. The tail of the skewed distribution represents the remaining 25% responding synapses, albeit at a strongly reduced efficacy. Comparing CTx-treated synapses with the control and combined CTx + Aga groups (Fig. 4B) reveals that the distribution of Rf values of CTx blocked synapses (red) is indistinguishable from the control condition (Rf 0.99 ± 0.32; mean ± SD). Thus blocking only N-type channels did neither affect the release properties of the entire synapse population, nor reveal a subpopulation of synapses entirely depended on N-type channels.

Bottom Line: Analysis of the release kinetics and the fractional release amplitude demonstrate that, whereas in only 15% of the synapses release depended exclusively on P/Q-type channels, the majority of synapses (85%) contained both N- and P/Q-type channels.Nevertheless, the kinetics of FM dye release in synapses containing both channel types was determined by the P/Q-type channels.Together, our data suggest a more direct coupling of P/Q-type channels to synaptic release compared to N-type channels, which may explain the high prevalence of neurological P/Q-type channelopathies.

View Article: PubMed Central - PubMed

Affiliation: Division of Physiology, Medical University Innsbruck, Fritz-Pregl-Str. 3, 6020 Innsbruck, Austria.

Show MeSH
Related in: MedlinePlus