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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 changes of afterhyperpolarisation (AHP) in Cav1.3 KO mice.(a/b) Whole-cell current clamp recordings of single action potentials of SN DA neurons from juvenile (a) and adult (b) WT and Cav1.3 KO mice, under control conditions and in the presence of L-type Ca2+ channel blocker (300 nM isradipine, blue bars). Dashed lines indicate −60 mV and −55 mV, respectively; scale bars: 20 mV/0.1 s. (c) Bar graphs display mean values ± SEM, and number of neurons analysed (n-values). WT data are given in black, Cav1.3 KO data in green. Note that SN DA AHPs from juvenile KO mice are significantly smaller while those of adult KO are significantly larger than those of respective WT mice. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
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f1: Age-dependent changes of afterhyperpolarisation (AHP) in Cav1.3 KO mice.(a/b) Whole-cell current clamp recordings of single action potentials of SN DA neurons from juvenile (a) and adult (b) WT and Cav1.3 KO mice, under control conditions and in the presence of L-type Ca2+ channel blocker (300 nM isradipine, blue bars). Dashed lines indicate −60 mV and −55 mV, respectively; scale bars: 20 mV/0.1 s. (c) Bar graphs display mean values ± SEM, and number of neurons analysed (n-values). WT data are given in black, Cav1.3 KO data in green. Note that SN DA AHPs from juvenile KO mice are significantly smaller while those of adult KO are significantly larger than those of respective WT mice. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.

Mentions: We first extensively compared a variety of basal biophysical properties of SN DA neurons from juvenile (PN13) and adult (PN90) wildtype (WT) and Cav1.3 KO mice using whole-cell patch-clamp analysis of in vitro brain-slices. No striking biophysical differences were observed (data not shown). However, the Ca2+-dependent afterhyperpolarisation (AHP) of spontaneous action potentials of SN DA neurons showed small but significant changes in Cav1.3 KO mice (Fig. 1 and Table 1). While the AHP was significantly smaller in SN DA neurons from juvenile Cav1.3 KO compared to those of juvenile WT (juvenile WT: −59.27 mV ± 0.6, n = 47; juvenile Cav1.3 KO: −55.26 mV ± 0.9, n = 40; U-value of the Wilcoxon-Mann-Whitney-U test, WMWU = 560, p = 0.001), it was significantly larger in SN DA neurons from adult Cav1.3 KO mice compared to those of adult WT (adult WT: −56.52 mV ± 0.8, n = 46; adult Cav1.3 KO: −59.75 mV ± 1.1, n = 22; WMWU = 327, p = 0.02). Of further note to these AHP changes is that the acute block of both, Cav1.2 and Cav1.3 LTCCs, by 300 nM isradipine had no effect on the AHPs of SN DA neurons from WT and Cav1.3 KO mice. The concentration of 300 nM isradipine was carefully chosen to avoid unspecific off-target effects (as described e.g. in17), while still providing efficient full block of Cav1.2 and Cav1.3 LTCCs61124 (see methods for details). These findings point to an age-dependent compensatory SN DA phenotype in the Cav1.3 KO mouse.


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 changes of afterhyperpolarisation (AHP) in Cav1.3 KO mice.(a/b) Whole-cell current clamp recordings of single action potentials of SN DA neurons from juvenile (a) and adult (b) WT and Cav1.3 KO mice, under control conditions and in the presence of L-type Ca2+ channel blocker (300 nM isradipine, blue bars). Dashed lines indicate −60 mV and −55 mV, respectively; scale bars: 20 mV/0.1 s. (c) Bar graphs display mean values ± SEM, and number of neurons analysed (n-values). WT data are given in black, Cav1.3 KO data in green. Note that SN DA AHPs from juvenile KO mice are significantly smaller while those of adult KO are significantly larger than those of respective WT mice. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4585382&req=5

f1: Age-dependent changes of afterhyperpolarisation (AHP) in Cav1.3 KO mice.(a/b) Whole-cell current clamp recordings of single action potentials of SN DA neurons from juvenile (a) and adult (b) WT and Cav1.3 KO mice, under control conditions and in the presence of L-type Ca2+ channel blocker (300 nM isradipine, blue bars). Dashed lines indicate −60 mV and −55 mV, respectively; scale bars: 20 mV/0.1 s. (c) Bar graphs display mean values ± SEM, and number of neurons analysed (n-values). WT data are given in black, Cav1.3 KO data in green. Note that SN DA AHPs from juvenile KO mice are significantly smaller while those of adult KO are significantly larger than those of respective WT mice. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
Mentions: We first extensively compared a variety of basal biophysical properties of SN DA neurons from juvenile (PN13) and adult (PN90) wildtype (WT) and Cav1.3 KO mice using whole-cell patch-clamp analysis of in vitro brain-slices. No striking biophysical differences were observed (data not shown). However, the Ca2+-dependent afterhyperpolarisation (AHP) of spontaneous action potentials of SN DA neurons showed small but significant changes in Cav1.3 KO mice (Fig. 1 and Table 1). While the AHP was significantly smaller in SN DA neurons from juvenile Cav1.3 KO compared to those of juvenile WT (juvenile WT: −59.27 mV ± 0.6, n = 47; juvenile Cav1.3 KO: −55.26 mV ± 0.9, n = 40; U-value of the Wilcoxon-Mann-Whitney-U test, WMWU = 560, p = 0.001), it was significantly larger in SN DA neurons from adult Cav1.3 KO mice compared to those of adult WT (adult WT: −56.52 mV ± 0.8, n = 46; adult Cav1.3 KO: −59.75 mV ± 1.1, n = 22; WMWU = 327, p = 0.02). Of further note to these AHP changes is that the acute block of both, Cav1.2 and Cav1.3 LTCCs, by 300 nM isradipine had no effect on the AHPs of SN DA neurons from WT and Cav1.3 KO mice. The concentration of 300 nM isradipine was carefully chosen to avoid unspecific off-target effects (as described e.g. in17), while still providing efficient full block of Cav1.2 and Cav1.3 LTCCs61124 (see methods for details). These findings point to an age-dependent compensatory SN DA phenotype in the Cav1.3 KO mouse.

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