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Cobb-Lewis DE, Sansalone L, Khaliq ZM. Contributions of the Sodium Leak Channel NALCN to Pacemaking of Medial Ventral Tegmental Area and Substantia Nigra Dopaminergic Neurons. J Neurosci 2023; 43:6841-6853. [PMID: 37640554 PMCID: PMC10573758 DOI: 10.1523/jneurosci.0930-22.2023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 08/04/2023] [Accepted: 08/10/2023] [Indexed: 08/31/2023] Open
Abstract
We tested the role of the sodium leak channel, NALCN, in pacemaking of dopaminergic neuron (DAN) subpopulations from adult male and female mice. In situ hybridization revealed NALCN RNA in all DANs, with lower abundance in medial ventral tegmental area (VTA) relative to substantia nigra pars compacta (SNc). Despite lower relative abundance of NALCN, we found that acute pharmacological blockade of NALCN in medial VTA DANs slowed pacemaking by 49.08%. We also examined the electrophysiological properties of projection-defined VTA DAN subpopulations identified by retrograde labeling. Inhibition of NALCN reduced pacemaking in DANs projecting to medial nucleus accumbens (NAc) and others projecting to lateral NAc by 70.74% and 31.98%, respectively, suggesting that NALCN is a primary driver of pacemaking in VTA DANs. In SNc DANs, potentiating NALCN by lowering extracellular calcium concentration speeded pacemaking in wildtype but not NALCN conditional knockout mice, demonstrating functional presence of NALCN. In contrast to VTA DANs, however, pacemaking in SNc DANs was unaffected by inhibition of NALCN. Instead, we found that inhibition of NALCN increased the gain of frequency-current plots at firing frequencies slower than spontaneous firing. Similarly, inhibition of the hyperpolarization-activated cyclic nucleotide-gated (HCN) conductance increased gain but had little effect on pacemaking. Interestingly, simultaneous inhibition of NALCN and HCN resulted in significant reduction in pacemaker rate. Thus, we found NALCN makes substantial contributions to driving pacemaking in VTA DAN subpopulations. In SNc DANs, NALCN is not critical for pacemaking but inhibition of NALCN makes cells more sensitive to hyperpolarizing stimuli.SIGNIFICANCE STATEMENT Pacemaking in midbrain dopaminergic neurons (DAN) relies on multiple subthreshold conductances, including a sodium leak. Whether the sodium leak channel, NALCN, contributes to pacemaking in DANs located in the VTA and the SNc has not yet been determined. Using electrophysiology and pharmacology, we show that NALCN plays a prominent role in driving pacemaking in projection-defined VTA DAN subpopulations. By contrast, pacemaking in SNc neurons does not rely on NALCN. Instead, the presence of NALCN regulates the excitability of SNc DANs by reducing the gain of the neuron's response to inhibitory stimuli. Together, these findings will inform future efforts to obtain DAN subpopulation-specific treatments for use in neuropsychiatric disorders.
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Affiliation(s)
- Dana E Cobb-Lewis
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
- Institute for Neuroscience, George Washington University School of Medicine and Health Sciences, Washington, DC 20037
| | - Lorenzo Sansalone
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
| | - Zayd M Khaliq
- Cellular Neurophysiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892
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Shin J, Kovacheva L, Thomas D, Stojanovic S, Knowlton CJ, Mankel J, Boehm J, Farassat N, Paladini C, Striessnig J, Canavier CC, Geisslinger G, Roeper J. Ca v1.3 calcium channels are full-range linear amplifiers of firing frequencies in lateral DA SN neurons. SCIENCE ADVANCES 2022; 8:eabm4560. [PMID: 35675413 PMCID: PMC9177074 DOI: 10.1126/sciadv.abm4560] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 04/22/2022] [Indexed: 05/12/2023]
Abstract
The low-threshold L-type calcium channel Cav1.3 accelerates the pacemaker rate in the heart, but its functional role for the extended dynamic range of neuronal firing is still unresolved. Here, we show that Cav1.3 calcium channels act as unexpectedly simple, full-range linear amplifiers of firing rates for lateral dopamine substantia nigra (DA SN) neurons in mice. This means that they boost in vitro or in vivo firing frequencies between 2 and 50 hertz by about 30%. Furthermore, we demonstrate that clinically relevant, low nanomolar concentrations of the L-type channel inhibitor isradipine selectively reduce the in vivo firing activity of these nigrostriatal DA SN neurons at therapeutic plasma concentrations. Thus, our study identifies the pacemaker function of neuronal Cav1.3 channels and provides direct evidence that repurposing dihydropyridines such as isradipine is feasible to selectively modulate the in vivo activity of highly vulnerable DA SN subpopulations in Parkinson's disease.
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Affiliation(s)
- Josef Shin
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Lora Kovacheva
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Dominique Thomas
- Pharmazentrum Frankfurt/ZAFES, Institute of Clinical Pharmacology, Frankfurt am Main, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP and Fraunhofer Cluster of Excellence for Immune Mediated Diseases CIMD, Frankfurt am Main, Germany
| | - Strahinja Stojanovic
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Christopher J. Knowlton
- Department of Cell Biology and Anatomy, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA, USA
| | - Johanna Mankel
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Johannes Boehm
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Navid Farassat
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
| | - Carlos Paladini
- UTSA Neuroscience Institute, University of Texas at San Antonio, San Antonio, TX, USA
| | - Jörg Striessnig
- University of Innsbruck, Department of Pharmacology and Toxicology, Center for Molecular Biosciences, Innsbruck, Austria
| | - Carmen C. Canavier
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP and Fraunhofer Cluster of Excellence for Immune Mediated Diseases CIMD, Frankfurt am Main, Germany
| | - Gerd Geisslinger
- Pharmazentrum Frankfurt/ZAFES, Institute of Clinical Pharmacology, Frankfurt am Main, Germany
- Fraunhofer Institute for Translational Medicine and Pharmacology ITMP and Fraunhofer Cluster of Excellence for Immune Mediated Diseases CIMD, Frankfurt am Main, Germany
| | - Jochen Roeper
- Goethe University, Institute of Neurophysiology, Neuroscience Center, Frankfurt am Main, Germany
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