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Compensatory T-type Ca2+ channel activity alters D2-autoreceptor responses of Substantia nigra dopamine neurons from Cav1.3 L-type Ca2+ channel KO mice.

Poetschke C, Dragicevic E, Duda J, Benkert J, Dougalis A, DeZio R, Snutch TP, Striessnig J, Liss B - Sci Rep (2015)

Bottom Line: This functional KO-phenotype was accompanied by cell-specific up-regulation of NCS-1 and Cav3.1-TTCC mRNA.Furthermore, in wildtype we identified an age-dependent switch of TTCC-function from contributing to SN DA pacemaker-precision in juveniles to pacemaker-frequency in adults.This novel interplay of Cav1.3 L-type and Cav3.1 T-type channels, and their modulation of SN DA activity-pattern and D2-AR-sensitisation, provide new insights into flexible age- and calcium-dependent activity-control of SN DA neurons and its pharmacological modulation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany.

ABSTRACT
The preferential degeneration of Substantia nigra dopamine midbrain neurons (SN DA) causes the motor-symptoms of Parkinson's disease (PD). Voltage-gated L-type calcium channels (LTCCs), especially the Cav1.3-subtype, generate an activity-related oscillatory Ca(2+) burden in SN DA neurons, contributing to their degeneration and PD. While LTCC-blockers are already in clinical trials as PD-therapy, age-dependent functional roles of Cav1.3 LTCCs in SN DA neurons remain unclear. Thus, we analysed juvenile and adult Cav1.3-deficient mice with electrophysiological and molecular techniques. To unmask compensatory effects, we compared Cav1.3 KO mice with pharmacological LTCC-inhibition. LTCC-function was not necessary for SN DA pacemaker-activity at either age, but rather contributed to their pacemaker-precision. Moreover, juvenile Cav1.3 KO but not WT mice displayed adult wildtype-like, sensitised inhibitory dopamine-D2-autoreceptor (D2-AR) responses that depended upon both, interaction of the neuronal calcium sensor NCS-1 with D2-ARs, and on voltage-gated T-type calcium channel (TTCC) activity. This functional KO-phenotype was accompanied by cell-specific up-regulation of NCS-1 and Cav3.1-TTCC mRNA. Furthermore, in wildtype we identified an age-dependent switch of TTCC-function from contributing to SN DA pacemaker-precision in juveniles to pacemaker-frequency in adults. This novel interplay of Cav1.3 L-type and Cav3.1 T-type channels, and their modulation of SN DA activity-pattern and D2-AR-sensitisation, provide new insights into flexible age- and calcium-dependent activity-control of SN DA neurons and its pharmacological modulation.

No MeSH data available.


Related in: MedlinePlus

Age-dependent T type Ca2+ channel modulation of pacemaker activity in SN DA neurons.(a/b) Exemplary perforated patch-clamp or cell-attached recordings of spontaneous activity of SN DA neurons from juvenile (a) and adult (b) WT mice without and with T-type channel inhibitor Z941 (pre-)incubation (10 μM, indicated by purple bars). Under each original 10 second trace, a 30 seconds schematic spike train representation is given. Arrows point to irregularity in pacemaker-activity in SN DA neurons from juvenile WT mice in Z941. (c) Data analysis as in Fig. 2 (d) Left: Mean SN DA pacemaker frequencies. Note that Z941 significantly reduced SN DA pacemaker frequency of adult WT SN DA but not of juvenile WT SN DA neuron. Right: Mean SN DA pacemaker precision, given as CV2 values. Note that Z941 significantly reduced pacemaker precision of juvenile WT SN DA but not adult WT SN DA neurons. All data are shown as mean ± SEM. Significant differences are marked by asterisks. Data values are detailed in Table 1.
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f4: Age-dependent T type Ca2+ channel modulation of pacemaker activity in SN DA neurons.(a/b) Exemplary perforated patch-clamp or cell-attached recordings of spontaneous activity of SN DA neurons from juvenile (a) and adult (b) WT mice without and with T-type channel inhibitor Z941 (pre-)incubation (10 μM, indicated by purple bars). Under each original 10 second trace, a 30 seconds schematic spike train representation is given. Arrows point to irregularity in pacemaker-activity in SN DA neurons from juvenile WT mice in Z941. (c) Data analysis as in Fig. 2 (d) Left: Mean SN DA pacemaker frequencies. Note that Z941 significantly reduced SN DA pacemaker frequency of adult WT SN DA but not of juvenile WT SN DA neuron. Right: Mean SN DA pacemaker precision, given as CV2 values. Note that Z941 significantly reduced pacemaker precision of juvenile WT SN DA but not adult WT SN DA neurons. All data are shown as mean ± SEM. Significant differences are marked by asterisks. Data values are detailed in Table 1.

Mentions: Given the functional coupling of D2-AR sensitisation to T-type Ca2+ channels, selectively in SN DA neurons from juvenile Cav1.3 KO mice, we addressed physiological age-dependent functional roles of TTCCs in wild-type SN DA neurons by comparing pacemaker activity and its precision in juvenile and adult mice. As summarised in Fig. 4 and Table 1, we gained evidence for differential functions of T-type currents in SN DA neurons from juvenile and adult WT mice. In juveniles, TTCC-activity stabilised pacemaker precision (CV2: juvenile WT: 3.87% ± 0.4, n = 7; juvenile WT in Z941: 6.69% ± 1; WMWU = 9, p = 0.03), similar as previously described2830, but did not change pacemaker activity. Of further note, the AHP differences between WT and Cav1.3 KO were abolished by TTCC-block (juvenile WT Z941: −59.06 mV ± 0.8, n = 17; juvenile Cav1.3 KO Z941: −58.4 mV ± 1.6, n = 14; WMWU = 118, p = 1, see Table 1). In adults in contrast, TTCC-block did not affect pacemaker precision, but reduced SN DA pacemaker frequency by about 30% (pacemaker frequency: adult WT: 3.2 Hz ± 0.2, n = 9; adult WT in Z941: 2.4 Hz ± 0.1, n = 13; WMWU = 20, p = 0.009). Furthermore, this impact of Z941 on adult SN DA pacemaker frequency was significantly pronounced in Cav1.3 KO compared to those of adult WT (pacemaker frequency: adult Cav1.3 KO: 3.3 Hz ± 0.3, n = 13; adult Cav1.3 KO in Z941: 1.4 Hz ± 0.1; WMWU = 3, p < 0.0001; adult WT in Z941 vs. adult Cav1.3 KO in Z941: WMWU = 6, p < 0.0001, see Table 1). This finding, together with the altered AHPs in SN DA neurons from Cav1.3 KOs (Fig. 1), point to an upregulation of TTCC currents in Cav1.3 KO.


Compensatory T-type Ca2+ channel activity alters D2-autoreceptor responses of Substantia nigra dopamine neurons from Cav1.3 L-type Ca2+ channel KO mice.

Poetschke C, Dragicevic E, Duda J, Benkert J, Dougalis A, DeZio R, Snutch TP, Striessnig J, Liss B - Sci Rep (2015)

Age-dependent T type Ca2+ channel modulation of pacemaker activity in SN DA neurons.(a/b) Exemplary perforated patch-clamp or cell-attached recordings of spontaneous activity of SN DA neurons from juvenile (a) and adult (b) WT mice without and with T-type channel inhibitor Z941 (pre-)incubation (10 μM, indicated by purple bars). Under each original 10 second trace, a 30 seconds schematic spike train representation is given. Arrows point to irregularity in pacemaker-activity in SN DA neurons from juvenile WT mice in Z941. (c) Data analysis as in Fig. 2 (d) Left: Mean SN DA pacemaker frequencies. Note that Z941 significantly reduced SN DA pacemaker frequency of adult WT SN DA but not of juvenile WT SN DA neuron. Right: Mean SN DA pacemaker precision, given as CV2 values. Note that Z941 significantly reduced pacemaker precision of juvenile WT SN DA but not adult WT SN DA neurons. All data are shown as mean ± SEM. Significant differences are marked by asterisks. Data values are detailed in Table 1.
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Related In: Results  -  Collection

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f4: Age-dependent T type Ca2+ channel modulation of pacemaker activity in SN DA neurons.(a/b) Exemplary perforated patch-clamp or cell-attached recordings of spontaneous activity of SN DA neurons from juvenile (a) and adult (b) WT mice without and with T-type channel inhibitor Z941 (pre-)incubation (10 μM, indicated by purple bars). Under each original 10 second trace, a 30 seconds schematic spike train representation is given. Arrows point to irregularity in pacemaker-activity in SN DA neurons from juvenile WT mice in Z941. (c) Data analysis as in Fig. 2 (d) Left: Mean SN DA pacemaker frequencies. Note that Z941 significantly reduced SN DA pacemaker frequency of adult WT SN DA but not of juvenile WT SN DA neuron. Right: Mean SN DA pacemaker precision, given as CV2 values. Note that Z941 significantly reduced pacemaker precision of juvenile WT SN DA but not adult WT SN DA neurons. All data are shown as mean ± SEM. Significant differences are marked by asterisks. Data values are detailed in Table 1.
Mentions: Given the functional coupling of D2-AR sensitisation to T-type Ca2+ channels, selectively in SN DA neurons from juvenile Cav1.3 KO mice, we addressed physiological age-dependent functional roles of TTCCs in wild-type SN DA neurons by comparing pacemaker activity and its precision in juvenile and adult mice. As summarised in Fig. 4 and Table 1, we gained evidence for differential functions of T-type currents in SN DA neurons from juvenile and adult WT mice. In juveniles, TTCC-activity stabilised pacemaker precision (CV2: juvenile WT: 3.87% ± 0.4, n = 7; juvenile WT in Z941: 6.69% ± 1; WMWU = 9, p = 0.03), similar as previously described2830, but did not change pacemaker activity. Of further note, the AHP differences between WT and Cav1.3 KO were abolished by TTCC-block (juvenile WT Z941: −59.06 mV ± 0.8, n = 17; juvenile Cav1.3 KO Z941: −58.4 mV ± 1.6, n = 14; WMWU = 118, p = 1, see Table 1). In adults in contrast, TTCC-block did not affect pacemaker precision, but reduced SN DA pacemaker frequency by about 30% (pacemaker frequency: adult WT: 3.2 Hz ± 0.2, n = 9; adult WT in Z941: 2.4 Hz ± 0.1, n = 13; WMWU = 20, p = 0.009). Furthermore, this impact of Z941 on adult SN DA pacemaker frequency was significantly pronounced in Cav1.3 KO compared to those of adult WT (pacemaker frequency: adult Cav1.3 KO: 3.3 Hz ± 0.3, n = 13; adult Cav1.3 KO in Z941: 1.4 Hz ± 0.1; WMWU = 3, p < 0.0001; adult WT in Z941 vs. adult Cav1.3 KO in Z941: WMWU = 6, p < 0.0001, see Table 1). This finding, together with the altered AHPs in SN DA neurons from Cav1.3 KOs (Fig. 1), point to an upregulation of TTCC currents in Cav1.3 KO.

Bottom Line: This functional KO-phenotype was accompanied by cell-specific up-regulation of NCS-1 and Cav3.1-TTCC mRNA.Furthermore, in wildtype we identified an age-dependent switch of TTCC-function from contributing to SN DA pacemaker-precision in juveniles to pacemaker-frequency in adults.This novel interplay of Cav1.3 L-type and Cav3.1 T-type channels, and their modulation of SN DA activity-pattern and D2-AR-sensitisation, provide new insights into flexible age- and calcium-dependent activity-control of SN DA neurons and its pharmacological modulation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany.

ABSTRACT
The preferential degeneration of Substantia nigra dopamine midbrain neurons (SN DA) causes the motor-symptoms of Parkinson's disease (PD). Voltage-gated L-type calcium channels (LTCCs), especially the Cav1.3-subtype, generate an activity-related oscillatory Ca(2+) burden in SN DA neurons, contributing to their degeneration and PD. While LTCC-blockers are already in clinical trials as PD-therapy, age-dependent functional roles of Cav1.3 LTCCs in SN DA neurons remain unclear. Thus, we analysed juvenile and adult Cav1.3-deficient mice with electrophysiological and molecular techniques. To unmask compensatory effects, we compared Cav1.3 KO mice with pharmacological LTCC-inhibition. LTCC-function was not necessary for SN DA pacemaker-activity at either age, but rather contributed to their pacemaker-precision. Moreover, juvenile Cav1.3 KO but not WT mice displayed adult wildtype-like, sensitised inhibitory dopamine-D2-autoreceptor (D2-AR) responses that depended upon both, interaction of the neuronal calcium sensor NCS-1 with D2-ARs, and on voltage-gated T-type calcium channel (TTCC) activity. This functional KO-phenotype was accompanied by cell-specific up-regulation of NCS-1 and Cav3.1-TTCC mRNA. Furthermore, in wildtype we identified an age-dependent switch of TTCC-function from contributing to SN DA pacemaker-precision in juveniles to pacemaker-frequency in adults. This novel interplay of Cav1.3 L-type and Cav3.1 T-type channels, and their modulation of SN DA activity-pattern and D2-AR-sensitisation, provide new insights into flexible age- and calcium-dependent activity-control of SN DA neurons and its pharmacological modulation.

No MeSH data available.


Related in: MedlinePlus