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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

Adult-like, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice.(a–c) Left: Perforated-patch clamp recordings of spontaneous activity of SN DA neurons from juvenile (a/b) and adult (c) WT and Cav1.3 KO mice. Application of dopamine (100 μM) is indicated by red bars, (pre-)incubation of isradipine (300 nM) is indicated by blue bars. Scale bars 20 mV/5 min. Right: Normalised frequencies plotted against time for all analysed SN DA neurons. Note the absence of a desensitisation of dopamine D2-autoreceptor (D2-AR) responses in juvenile KO mice compared to WT, and that in contrast, acute block of L-type Ca2+ channels (LTCCs) did not alter D2-AR responses of juvenile WT or KO mice. (d) Left: Mean SN DA pacemaker frequencies before dopamine application. Note that neither chronic loss of Cav1.3 nor acute LTCC-block (isradipine) altered SN DA pacemaker frequency. Middle: Mean SN DA pacemaker precision, given as the less firing-rate dependent interspike interval derived CV2 values. Right: SN DA D2-AR responses, given as mean relative spontaneous activity at the last minute of dopamine application (min 15) in relation to respective basal pacemaker frequencies. Note that the prominent desensitisation of D2-AR responses of juvenile SN DA neurons from WT mice was absent in the KO, but not in acute LTCC-blocker. All data are shown as the mean ± SEM. WT data are shown in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics detailed in Table 1.
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f2: Adult-like, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice.(a–c) Left: Perforated-patch clamp recordings of spontaneous activity of SN DA neurons from juvenile (a/b) and adult (c) WT and Cav1.3 KO mice. Application of dopamine (100 μM) is indicated by red bars, (pre-)incubation of isradipine (300 nM) is indicated by blue bars. Scale bars 20 mV/5 min. Right: Normalised frequencies plotted against time for all analysed SN DA neurons. Note the absence of a desensitisation of dopamine D2-autoreceptor (D2-AR) responses in juvenile KO mice compared to WT, and that in contrast, acute block of L-type Ca2+ channels (LTCCs) did not alter D2-AR responses of juvenile WT or KO mice. (d) Left: Mean SN DA pacemaker frequencies before dopamine application. Note that neither chronic loss of Cav1.3 nor acute LTCC-block (isradipine) altered SN DA pacemaker frequency. Middle: Mean SN DA pacemaker precision, given as the less firing-rate dependent interspike interval derived CV2 values. Right: SN DA D2-AR responses, given as mean relative spontaneous activity at the last minute of dopamine application (min 15) in relation to respective basal pacemaker frequencies. Note that the prominent desensitisation of D2-AR responses of juvenile SN DA neurons from WT mice was absent in the KO, but not in acute LTCC-blocker. All data are shown as the mean ± SEM. WT data are shown in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics detailed in Table 1.

Mentions: A possible age-dependent contribution of LTCCs to generation of pacemaker-activity of SN DA neurons is controversial171819. Thus, we analysed the spontaneous pacemaker frequency and its precision (given as the coefficient of variation (CV) of the interspike interval (ISI), and as CV2 values) of SN DA neurons from juvenile and adult WT and Cav1.3 KO mice using in vitro brain-slices. Further, we analysed pacemaker-activity in response to acute dopamine application (100 μM) in order to address D2-AR responses. Perforated patch-clamp recordings allowed unperturbed physiological activity and signalling of SN DA neurons to be assessed. As summarised in Fig. 2d (left) and Table 1, pacemaker frequencies of juvenile or adult SN DA neurons were neither significantly altered due to acute LTCC pharmacological inhibition, nor affected by chronic Cav1.3 loss in the global KO mice. However, LTCCs seem to stabilise pacemaker precision, since Cav1.3 KO neurons displayed less regular pacemaker-activities as evident from the respective CV2 values (compare Fig. 2d and Table 1; CV2-values: juvenile WT: 3.87% ± 0.4, n = 7; juvenile Cav1.3 KO: 7.71% ± 2, n = 9; WMWU = 19, p = 0.2; juvenile WT isradipine: 3.73% ± 0.8, n = 8; juvenile Cav1.3 KO isradipine: 8.88% ± 2.6, n = 8; WMWU = 12, p = 0.04; adult WT: 2.92% ± 0.7, n = 5; adult Cav1.3 KO: 5.35% ± 1, n = 6; WMWU = 4, p = 0.05).


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)

Adult-like, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice.(a–c) Left: Perforated-patch clamp recordings of spontaneous activity of SN DA neurons from juvenile (a/b) and adult (c) WT and Cav1.3 KO mice. Application of dopamine (100 μM) is indicated by red bars, (pre-)incubation of isradipine (300 nM) is indicated by blue bars. Scale bars 20 mV/5 min. Right: Normalised frequencies plotted against time for all analysed SN DA neurons. Note the absence of a desensitisation of dopamine D2-autoreceptor (D2-AR) responses in juvenile KO mice compared to WT, and that in contrast, acute block of L-type Ca2+ channels (LTCCs) did not alter D2-AR responses of juvenile WT or KO mice. (d) Left: Mean SN DA pacemaker frequencies before dopamine application. Note that neither chronic loss of Cav1.3 nor acute LTCC-block (isradipine) altered SN DA pacemaker frequency. Middle: Mean SN DA pacemaker precision, given as the less firing-rate dependent interspike interval derived CV2 values. Right: SN DA D2-AR responses, given as mean relative spontaneous activity at the last minute of dopamine application (min 15) in relation to respective basal pacemaker frequencies. Note that the prominent desensitisation of D2-AR responses of juvenile SN DA neurons from WT mice was absent in the KO, but not in acute LTCC-blocker. All data are shown as the mean ± SEM. WT data are shown in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics detailed in Table 1.
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f2: Adult-like, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice.(a–c) Left: Perforated-patch clamp recordings of spontaneous activity of SN DA neurons from juvenile (a/b) and adult (c) WT and Cav1.3 KO mice. Application of dopamine (100 μM) is indicated by red bars, (pre-)incubation of isradipine (300 nM) is indicated by blue bars. Scale bars 20 mV/5 min. Right: Normalised frequencies plotted against time for all analysed SN DA neurons. Note the absence of a desensitisation of dopamine D2-autoreceptor (D2-AR) responses in juvenile KO mice compared to WT, and that in contrast, acute block of L-type Ca2+ channels (LTCCs) did not alter D2-AR responses of juvenile WT or KO mice. (d) Left: Mean SN DA pacemaker frequencies before dopamine application. Note that neither chronic loss of Cav1.3 nor acute LTCC-block (isradipine) altered SN DA pacemaker frequency. Middle: Mean SN DA pacemaker precision, given as the less firing-rate dependent interspike interval derived CV2 values. Right: SN DA D2-AR responses, given as mean relative spontaneous activity at the last minute of dopamine application (min 15) in relation to respective basal pacemaker frequencies. Note that the prominent desensitisation of D2-AR responses of juvenile SN DA neurons from WT mice was absent in the KO, but not in acute LTCC-blocker. All data are shown as the mean ± SEM. WT data are shown in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics detailed in Table 1.
Mentions: A possible age-dependent contribution of LTCCs to generation of pacemaker-activity of SN DA neurons is controversial171819. Thus, we analysed the spontaneous pacemaker frequency and its precision (given as the coefficient of variation (CV) of the interspike interval (ISI), and as CV2 values) of SN DA neurons from juvenile and adult WT and Cav1.3 KO mice using in vitro brain-slices. Further, we analysed pacemaker-activity in response to acute dopamine application (100 μM) in order to address D2-AR responses. Perforated patch-clamp recordings allowed unperturbed physiological activity and signalling of SN DA neurons to be assessed. As summarised in Fig. 2d (left) and Table 1, pacemaker frequencies of juvenile or adult SN DA neurons were neither significantly altered due to acute LTCC pharmacological inhibition, nor affected by chronic Cav1.3 loss in the global KO mice. However, LTCCs seem to stabilise pacemaker precision, since Cav1.3 KO neurons displayed less regular pacemaker-activities as evident from the respective CV2 values (compare Fig. 2d and Table 1; CV2-values: juvenile WT: 3.87% ± 0.4, n = 7; juvenile Cav1.3 KO: 7.71% ± 2, n = 9; WMWU = 19, p = 0.2; juvenile WT isradipine: 3.73% ± 0.8, n = 8; juvenile Cav1.3 KO isradipine: 8.88% ± 2.6, n = 8; WMWU = 12, p = 0.04; adult WT: 2.92% ± 0.7, n = 5; adult Cav1.3 KO: 5.35% ± 1, n = 6; WMWU = 4, p = 0.05).

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