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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

Calcium-dependent, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice are mediated by T-type Ca2+ channels and the neuronal calcium sensor NCS-1.Dopamine D2-AR experiments and SN DA data presentation are similar to that for Fig. 2. (a) Experiments in the presence of 10 mM EGTA (whole-cell current clamp), to buffer free internal Ca2+ in SN DA neurons from juvenile WT (n = 6) and Cav1.3 KO (n = 7) mice. (b) Experiments in the presence of either DNIP (yellow, D2/NCS-1 interacting peptide) or scrambled DNIP (as controls, blue, srDNIP) to block D2-AR/NCS-1 interactions in SN DA neurons from juvenile Cav1.3 KO mice (DNIP: n = 11; srDNIP: n = 10, perforated patch or on-cell recordings). Mean basal pacemaker frequencies were not affected by DNIP (see Table 1). (c) Experiments in the presence of the T-type Ca2+ channel blocker Z941 (10 μM; purple bar, perforated patch) in SN DA neurons from juvenile WT (n = 10) and Cav1.3 KO (n = 8). (d) Activity of SN DA neurons from (a–c) (and from Fig. 2a) at the last minute of dopamine application (min 15). Note that buffering of free internal Ca2+ (EGTA) is inducing prominent D2-AR desensitisation in both SN DA neurons from juvenile WT and KO mice, while DNIP (but not srDNIP), as well as Z941, both introduce WT-like D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice. All data are shown as mean ± SEM, WT data in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
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f3: Calcium-dependent, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice are mediated by T-type Ca2+ channels and the neuronal calcium sensor NCS-1.Dopamine D2-AR experiments and SN DA data presentation are similar to that for Fig. 2. (a) Experiments in the presence of 10 mM EGTA (whole-cell current clamp), to buffer free internal Ca2+ in SN DA neurons from juvenile WT (n = 6) and Cav1.3 KO (n = 7) mice. (b) Experiments in the presence of either DNIP (yellow, D2/NCS-1 interacting peptide) or scrambled DNIP (as controls, blue, srDNIP) to block D2-AR/NCS-1 interactions in SN DA neurons from juvenile Cav1.3 KO mice (DNIP: n = 11; srDNIP: n = 10, perforated patch or on-cell recordings). Mean basal pacemaker frequencies were not affected by DNIP (see Table 1). (c) Experiments in the presence of the T-type Ca2+ channel blocker Z941 (10 μM; purple bar, perforated patch) in SN DA neurons from juvenile WT (n = 10) and Cav1.3 KO (n = 8). (d) Activity of SN DA neurons from (a–c) (and from Fig. 2a) at the last minute of dopamine application (min 15). Note that buffering of free internal Ca2+ (EGTA) is inducing prominent D2-AR desensitisation in both SN DA neurons from juvenile WT and KO mice, while DNIP (but not srDNIP), as well as Z941, both introduce WT-like D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice. All data are shown as mean ± SEM, WT data in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.

Mentions: To further define a functional compensatory phenotype in juvenile Cav1.3 KO mice, we next studied whether the mechanism of SN DA D2-AR desensitisation downstream of Cav1.3 was similar in the Cav1.3 KO to the Ca2+ sensor NCS-1 mechanism that we identified for WT mice11. To determine if D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice depended on free intracellular Ca2+ and interaction of NCS-1 with D2-ARs, we buffered internal Ca2+ with 10 mM EGTA (whole-cell; Fig. 3a,d and Table 1), and in a second experiment we applied a membrane permeable peptide that prevents D2-R/NCS-1 interactions (perforated patch; DNIP, or scrambled DNIP (srDNIP) as control1126; Fig. 3b,d and Table 1). Internal Ca2+ buffering induced prominently desensitising D2-AR responses in SN DA neurons from both, juvenile WT and Cav1.3 KO mice (Fig. 3b,d and Table 1). Furthermore, the presence of the DNIP peptide (but not srDNIP) re-stored WT-like desensitising D2-AR responses in SN DA neurons from juvenile Cav1.3 KO mice (Fig. 3b,d and Table 1). These findings strongly suggest that the D2-AR desensitisation mechanism downstream of the Ca2+ source is not altered in SN DA neurons from Cav1.3 KO mice and relies — as in WT — on Ca2+-dependent NCS-1/D2-AR interactions11. These findings also indicate an alternative, compensatory Ca2+ source in SN DA neurons from Cav1.3 KO mice, mediating NCS-1/D2-AR interactions and the observed reduction in D2-AR desensitisation.


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)

Calcium-dependent, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice are mediated by T-type Ca2+ channels and the neuronal calcium sensor NCS-1.Dopamine D2-AR experiments and SN DA data presentation are similar to that for Fig. 2. (a) Experiments in the presence of 10 mM EGTA (whole-cell current clamp), to buffer free internal Ca2+ in SN DA neurons from juvenile WT (n = 6) and Cav1.3 KO (n = 7) mice. (b) Experiments in the presence of either DNIP (yellow, D2/NCS-1 interacting peptide) or scrambled DNIP (as controls, blue, srDNIP) to block D2-AR/NCS-1 interactions in SN DA neurons from juvenile Cav1.3 KO mice (DNIP: n = 11; srDNIP: n = 10, perforated patch or on-cell recordings). Mean basal pacemaker frequencies were not affected by DNIP (see Table 1). (c) Experiments in the presence of the T-type Ca2+ channel blocker Z941 (10 μM; purple bar, perforated patch) in SN DA neurons from juvenile WT (n = 10) and Cav1.3 KO (n = 8). (d) Activity of SN DA neurons from (a–c) (and from Fig. 2a) at the last minute of dopamine application (min 15). Note that buffering of free internal Ca2+ (EGTA) is inducing prominent D2-AR desensitisation in both SN DA neurons from juvenile WT and KO mice, while DNIP (but not srDNIP), as well as Z941, both introduce WT-like D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice. All data are shown as mean ± SEM, WT data in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
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f3: Calcium-dependent, sensitised D2-autoreceptor responses in SN DA neurons from juvenile Cav1.3 KO mice are mediated by T-type Ca2+ channels and the neuronal calcium sensor NCS-1.Dopamine D2-AR experiments and SN DA data presentation are similar to that for Fig. 2. (a) Experiments in the presence of 10 mM EGTA (whole-cell current clamp), to buffer free internal Ca2+ in SN DA neurons from juvenile WT (n = 6) and Cav1.3 KO (n = 7) mice. (b) Experiments in the presence of either DNIP (yellow, D2/NCS-1 interacting peptide) or scrambled DNIP (as controls, blue, srDNIP) to block D2-AR/NCS-1 interactions in SN DA neurons from juvenile Cav1.3 KO mice (DNIP: n = 11; srDNIP: n = 10, perforated patch or on-cell recordings). Mean basal pacemaker frequencies were not affected by DNIP (see Table 1). (c) Experiments in the presence of the T-type Ca2+ channel blocker Z941 (10 μM; purple bar, perforated patch) in SN DA neurons from juvenile WT (n = 10) and Cav1.3 KO (n = 8). (d) Activity of SN DA neurons from (a–c) (and from Fig. 2a) at the last minute of dopamine application (min 15). Note that buffering of free internal Ca2+ (EGTA) is inducing prominent D2-AR desensitisation in both SN DA neurons from juvenile WT and KO mice, while DNIP (but not srDNIP), as well as Z941, both introduce WT-like D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice. All data are shown as mean ± SEM, WT data in black and KO data in green. Significant differences are marked by asterisks. Data values and statistics are detailed in Table 1.
Mentions: To further define a functional compensatory phenotype in juvenile Cav1.3 KO mice, we next studied whether the mechanism of SN DA D2-AR desensitisation downstream of Cav1.3 was similar in the Cav1.3 KO to the Ca2+ sensor NCS-1 mechanism that we identified for WT mice11. To determine if D2-AR desensitisation in SN DA neurons from juvenile Cav1.3 KO mice depended on free intracellular Ca2+ and interaction of NCS-1 with D2-ARs, we buffered internal Ca2+ with 10 mM EGTA (whole-cell; Fig. 3a,d and Table 1), and in a second experiment we applied a membrane permeable peptide that prevents D2-R/NCS-1 interactions (perforated patch; DNIP, or scrambled DNIP (srDNIP) as control1126; Fig. 3b,d and Table 1). Internal Ca2+ buffering induced prominently desensitising D2-AR responses in SN DA neurons from both, juvenile WT and Cav1.3 KO mice (Fig. 3b,d and Table 1). Furthermore, the presence of the DNIP peptide (but not srDNIP) re-stored WT-like desensitising D2-AR responses in SN DA neurons from juvenile Cav1.3 KO mice (Fig. 3b,d and Table 1). These findings strongly suggest that the D2-AR desensitisation mechanism downstream of the Ca2+ source is not altered in SN DA neurons from Cav1.3 KO mice and relies — as in WT — on Ca2+-dependent NCS-1/D2-AR interactions11. These findings also indicate an alternative, compensatory Ca2+ source in SN DA neurons from Cav1.3 KO mice, mediating NCS-1/D2-AR interactions and the observed reduction in D2-AR desensitisation.

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