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Jang J, Kim SH, Um KB, Kim HJ, Park MK. Somatodendritic organization of pacemaker activity in midbrain dopamine neurons. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2024; 28:165-181. [PMID: 38414399 PMCID: PMC10902590 DOI: 10.4196/kjpp.2024.28.2.165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 01/08/2024] [Accepted: 01/08/2024] [Indexed: 02/29/2024]
Abstract
The slow and regular pacemaking activity of midbrain dopamine (DA) neurons requires proper spatial organization of the excitable elements between the soma and dendritic compartments, but the somatodendritic organization is not clear. Here, we show that the dynamic interaction between the soma and multiple proximal dendritic compartments (PDCs) generates the slow pacemaking activity in DA neurons. In multipolar DA neurons, spontaneous action potentials (sAPs) consistently originate from the axon-bearing dendrite. However, when the axon initial segment was disabled, sAPs emerge randomly from various primary PDCs, indicating that multiple PDCs drive pacemaking. Ca2+ measurements and local stimulation/perturbation experiments suggest that the soma serves as a stably-oscillating inertial compartment, while multiple PDCs exhibit stochastic fluctuations and high excitability. Despite the stochastic and excitable nature of PDCs, their activities are balanced by the large centrally-connected inertial soma, resulting in the slow synchronized pacemaking rhythm. Furthermore, our electrophysiological experiments indicate that the soma and PDCs, with distinct characteristics, play different roles in glutamate- induced burst-pause firing patterns. Excitable PDCs mediate excitatory burst responses to glutamate, while the large inertial soma determines inhibitory pause responses to glutamate. Therefore, we could conclude that this somatodendritic organization serves as a common foundation for both pacemaker activity and evoked firing patterns in midbrain DA neurons.
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Affiliation(s)
- Jinyoung Jang
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - Shin Hye Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - Ki Bum Um
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - Hyun Jin Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
| | - Myoung Kyu Park
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 16419, Korea
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Blankenship HE, Carter KA, Cassidy NT, Markiewicz AN, Thellmann MI, Sharpe AL, Freeman WM, Beckstead MJ. VTA dopamine neurons are hyperexcitable in 3xTg-AD mice due to casein kinase 2-dependent SK channel dysfunction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.16.567486. [PMID: 38014232 PMCID: PMC10680865 DOI: 10.1101/2023.11.16.567486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Alzheimer's disease (AD) patients exhibit neuropsychiatric symptoms that extend beyond classical cognitive deficits, suggesting involvement of subcortical areas. Here, we investigated the role of midbrain dopamine (DA) neurons in AD using the amyloid + tau-driven 3xTg-AD mouse model. We found deficits in reward-based operant learning in AD mice, suggesting possible VTA DA neuron dysregulation. Physiological assessment revealed hyperexcitability and disrupted firing in DA neurons caused by reduced activity of small-conductance calcium-activated potassium (SK) channels. RNA sequencing from contents of single patch-clamped DA neurons (Patch-seq) identified up-regulation of the SK channel modulator casein kinase 2 (CK2). Pharmacological inhibition of CK2 restored SK channel activity and normal firing patterns in 3xTg-AD mice. These findings shed light on a complex interplay between neuropsychiatric symptoms and subcortical circuits in AD, paving the way for novel treatment strategies.
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Beccano-Kelly DA, Cherubini M, Mousba Y, Cramb KM, Giussani S, Caiazza MC, Rai P, Vingill S, Bengoa-Vergniory N, Ng B, Corda G, Banerjee A, Vowles J, Cowley S, Wade-Martins R. Calcium dysregulation combined with mitochondrial failure and electrophysiological maturity converge in Parkinson's iPSC-dopamine neurons. iScience 2023; 26:107044. [PMID: 37426342 PMCID: PMC10329047 DOI: 10.1016/j.isci.2023.107044] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/30/2022] [Accepted: 06/01/2023] [Indexed: 07/11/2023] Open
Abstract
Parkinson's disease (PD) is characterized by a progressive deterioration of motor and cognitive functions. Although death of dopamine neurons is the hallmark pathology of PD, this is a late-stage disease process preceded by neuronal dysfunction. Here we describe early physiological perturbations in patient-derived induced pluripotent stem cell (iPSC)-dopamine neurons carrying the GBA-N370S mutation, a strong genetic risk factor for PD. GBA-N370S iPSC-dopamine neurons show an early and persistent calcium dysregulation notably at the mitochondria, followed by reduced mitochondrial membrane potential and oxygen consumption rate, indicating mitochondrial failure. With increased neuronal maturity, we observed decreased synaptic function in PD iPSC-dopamine neurons, consistent with the requirement for ATP and calcium to support the increase in electrophysiological activity over time. Our work demonstrates that calcium dyshomeostasis and mitochondrial failure impair the higher electrophysiological activity of mature neurons and may underlie the vulnerability of dopamine neurons in PD.
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Affiliation(s)
- Dayne A. Beccano-Kelly
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Marta Cherubini
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Yassine Mousba
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Kaitlyn M.L. Cramb
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford OX1 3QU, UK
| | - Stefania Giussani
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Maria Claudia Caiazza
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford OX1 3QU, UK
| | - Pavandeep Rai
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Siv Vingill
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Nora Bengoa-Vergniory
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford OX1 3QU, UK
| | - Bryan Ng
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford OX1 3QU, UK
| | - Gabriele Corda
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
| | - Abhirup Banerjee
- Radcliffe Department of Medicine, Division of Cardiovascular Medicine, University of Oxford, Oxford OX3 9DU, UK
- Department of Engineering Science, Institute of Biomedical Engineering, University of Oxford, Oxford OX3 7DQ, UK
| | - Jane Vowles
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- The James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Sally Cowley
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- The James Martin Stem Cell Facility, Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, UK
| | - Richard Wade-Martins
- Oxford Parkinson’s Disease Centre, University of Oxford, Oxford, United Kingdom
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX3 7BN, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, South Parks Road, Oxford OX1 3QU, UK
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Kwon YJ, Kwon OI, Hwang HJ, Shin HC, Yang S. Therapeutic effects of phlorotannins in the treatment of neurodegenerative disorders. Front Mol Neurosci 2023; 16:1193590. [PMID: 37305552 PMCID: PMC10249478 DOI: 10.3389/fnmol.2023.1193590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 04/27/2023] [Indexed: 06/13/2023] Open
Abstract
Phlorotannins are natural polyphenolic compounds produced by brown marine algae and are currently found in nutritional supplements. Although they are known to cross the blood-brain barrier, their neuropharmacological actions remain unclear. Here we review the potential therapeutic benefits of phlorotannins in the treatment of neurodegenerative diseases. In mouse models of Alzheimer's disease, ethanol intoxication and fear stress, the phlorotannin monomer phloroglucinol and the compounds eckol, dieckol and phlorofucofuroeckol A have been shown to improve cognitive function. In a mouse model of Parkinson's disease, phloroglucinol treatment led to improved motor performance. Additional neurological benefits associated with phlorotannin intake have been demonstrated in stroke, sleep disorders, and pain response. These effects may stem from the inhibition of disease-inducing plaque synthesis and aggregation, suppression of microglial activation, modulation of pro-inflammatory signaling, reduction of glutamate-induced excitotoxicity, and scavenging of reactive oxygen species. Clinical trials of phlorotannins have not reported significant adverse effects, suggesting these compounds to be promising bioactive agents in the treatment of neurological diseases. We therefore propose a putative biophysical mechanism of phlorotannin action in addition to future directions for phlorotannin research.
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Affiliation(s)
- Yoon Ji Kwon
- Department of Neuroscience, City University of Hong Kong, Kowloon, Hong Kong SAR, China
| | - Oh Ig Kwon
- Botamedi Brain Health and Medical Care Company Limited, Central, Hong Kong SAR, China
| | - Hye Jeong Hwang
- Center for Molecular Intelligence, SUNY Korea, Incheon, Republic of Korea
| | - Hyeon-Cheol Shin
- Botamedi Brain Health and Medical Care Company Limited, Central, Hong Kong SAR, China
- Center for Molecular Intelligence, SUNY Korea, Incheon, Republic of Korea
| | - Sungchil Yang
- Department of Neuroscience, City University of Hong Kong, Kowloon, Hong Kong SAR, China
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Elsayed OH, El-Mallakh RS. Catatonia Secondary to Depolarization Block. Asian J Psychiatr 2023; 84:103543. [PMID: 37028234 DOI: 10.1016/j.ajp.2023.103543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/18/2023] [Accepted: 03/13/2023] [Indexed: 04/09/2023]
Abstract
Catatonia is a severe psychomotor disorder that is associated with a 60-fold increased risk of premature death. Its occurrence has been associated with multiple psychiatric diagnoses, the most common being type I bipolar disorder. Catatonia can be understood as a disorder of ion dysregulation with reduced clearance of intracellular sodium ions. As the intraneuronal sodium concentration increases, the transmembrane potential is increased, and the resting potential may ultimately depolarize above the cellular threshold potential creating a condition known as depolarization block. Neurons in depolarization block do not respond to stimulation but are constantly releasing neurotransmitter; they mirror the clinical state of catatonia - active but non-responsive. Hyperpolarizing neurons, e.g., with benzodiazepines, is the most effective treatment.
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Affiliation(s)
- Omar H Elsayed
- Mood Disorders Research Program, Depression Center, Department of Psychiatry and Behavioral Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA
| | - Rif S El-Mallakh
- Mood Disorders Research Program, Depression Center, Department of Psychiatry and Behavioral Sciences, University of Louisville School of Medicine, Louisville, KY 40202, USA.
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McKinney A, Hu M, Hoskins A, Mohammadyar A, Naeem N, Jing J, Patel SS, Sheth BR, Jiang X. Cellular composition and circuit organization of the locus coeruleus of adult mice. eLife 2023; 12:e80100. [PMID: 36734517 PMCID: PMC9934863 DOI: 10.7554/elife.80100] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 02/01/2023] [Indexed: 02/04/2023] Open
Abstract
The locus coeruleus (LC) houses the vast majority of noradrenergic neurons in the brain and regulates many fundamental functions, including fight and flight response, attention control, and sleep/wake cycles. While efferent projections of the LC have been extensively investigated, little is known about its local circuit organization. Here, we performed large-scale multipatch recordings of noradrenergic neurons in adult mouse LC to profile their morpho-electric properties while simultaneously examining their interactions. LC noradrenergic neurons are diverse and could be classified into two major morpho-electric types. While fast excitatory synaptic transmission among LC noradrenergic neurons was not observed in our preparation, these mature LC neurons connected via gap junction at a rate similar to their early developmental stage and comparable to other brain regions. Most electrical connections form between dendrites and are restricted to narrowly spaced pairs or small clusters of neurons of the same type. In addition, more than two electrically coupled cell pairs were often identified across a cohort of neurons from individual multicell recording sets that followed a chain-like organizational pattern. The assembly of LC noradrenergic neurons thus follows a spatial and cell-type-specific wiring principle that may be imposed by a unique chain-like rule.
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Affiliation(s)
- Andrew McKinney
- Neuroscience Graduate Program, Baylor College of MedicineHoustonUnited States
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s HospitalHoustonUnited States
| | - Ming Hu
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s HospitalHoustonUnited States
| | | | | | | | - Junzhan Jing
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s HospitalHoustonUnited States
| | - Saumil S Patel
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
| | - Bhavin R Sheth
- Department of Electrical and Computer Engineering, University of HoustonHoustonUnited States
- Center for NeuroEngineering and Cognitive Science, University of HoustonHoustonUnited States
| | - Xiaolong Jiang
- Neuroscience Graduate Program, Baylor College of MedicineHoustonUnited States
- Department of Neuroscience, Baylor College of MedicineHoustonUnited States
- Jan and Dan Duncan Neurological Research Institute at Texas Children’s HospitalHoustonUnited States
- Department of Ophthalmology, Baylor College of MedicineHoustonUnited States
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Tomagra G, Franchino C, Cesano F, Chiarion G, de lure A, Carbone E, Calabresi P, Mesin L, Picconi B, Marcantoni A, Carabelli V. Alpha-synuclein oligomers alter the spontaneous firing discharge of cultured midbrain neurons. Front Cell Neurosci 2023; 17:1078550. [PMID: 36744002 PMCID: PMC9896582 DOI: 10.3389/fncel.2023.1078550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/06/2023] [Indexed: 01/21/2023] Open
Abstract
The aim of this work was to monitor the effects of extracellular α-synuclein on the firing activity of midbrain neurons dissociated from substantia nigra TH-GFP mice embryos and cultured on microelectrode arrays (MEA). We monitored the spontaneous firing discharge of the network for 21 days after plating and the role of glutamatergic and GABAergic inputs in regulating burst generation and network synchronism. Addition of GABA A , AMPA and NMDA antagonists did not suppress the spontaneous activity but allowed to identify three types of neurons that exhibited different modalities of firing and response to applied L-DOPA: high-rate (HR) neurons, low-rate pacemaking (LR-p), and low-rate non-pacemaking (LR-np) neurons. Most HR neurons were insensitive to L-DOPA, while the majority of LR-p neurons responded with a decrease of the firing discharge; less defined was the response of LR-np neurons. The effect of exogenous α-synuclein (α-syn) on the firing discharge of midbrain neurons was then studied by varying the exposure time (0-48 h) and the α-syn concentration (0.3-70 μM), while the formation of α-syn oligomers was monitored by means of AFM. Independently of the applied concentration, acute exposure to α-syn monomers did not exert any effect on the spontaneous firing rate of HR, LR-p, and LR-np neurons. On the contrary, after 48 h exposure, the firing activity was drastically altered at late developmental stages (14 days in vitro, DIV, neurons): α-syn oligomers progressively reduced the spontaneous firing discharge (IC50 = 1.03 μM), impaired burst generation and network synchronism, proportionally to the increased oligomer/monomer ratio. Different effects were found on early-stage developed neurons (9 DIV), whose firing discharge remained unaltered, regardless of the applied α-syn concentration and the exposure time. Our findings unravel, for the first time, the variable effects of exogenous α-syn at different stages of midbrain network development and provide new evidence for the early detection of neuronal function impairment associated to aggregated forms of α-syn.
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Affiliation(s)
- Giulia Tomagra
- Drug Science Department, University of Torino, Turin, Italy
- Nanostructured Interfaces and Surfaces Inter-Departmental Research Centre, Turin, Italy
| | | | - Federico Cesano
- Nanostructured Interfaces and Surfaces Inter-Departmental Research Centre, Turin, Italy
- Department of Chemistry and INSTM-UdR Torino, Turin, Italy
| | - Giovanni Chiarion
- Mathematical Biology and Physiology, Department of Electronics and Telecommunications, Turin, Italy
| | - Antonio de lure
- Laboratory Experimental Neurophysiology, IRCCS San Raffaele Rome, Rome, Italy
| | - Emilio Carbone
- Drug Science Department, University of Torino, Turin, Italy
- Nanostructured Interfaces and Surfaces Inter-Departmental Research Centre, Turin, Italy
| | - Paolo Calabresi
- Neurological Clinic, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy
- Neurology, Department of Neuroscience, Faculty of Medicine, Università Cattolica del “Sacro Cuore,”Rome, Italy
| | - Luca Mesin
- Mathematical Biology and Physiology, Department of Electronics and Telecommunications, Turin, Italy
| | - Barbara Picconi
- Laboratory Experimental Neurophysiology, IRCCS San Raffaele Rome, Rome, Italy
- Dipartimento di Scienze Umane e Promozione della Qualitá della Vita, Telematic University San Raffaele Roma, Rome, Italy
| | - Andrea Marcantoni
- Drug Science Department, University of Torino, Turin, Italy
- Nanostructured Interfaces and Surfaces Inter-Departmental Research Centre, Turin, Italy
| | - Valentina Carabelli
- Drug Science Department, University of Torino, Turin, Italy
- Nanostructured Interfaces and Surfaces Inter-Departmental Research Centre, Turin, Italy
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Hahn S, Um KB, Kim SW, Kim HJ, Park MK. Proximal dendritic localization of NALCN channels underlies tonic and burst firing in nigral dopaminergic neurons. J Physiol 2023; 601:171-193. [PMID: 36398712 DOI: 10.1113/jp283716] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 11/14/2022] [Indexed: 11/19/2022] Open
Abstract
In multipolar nigral dopamine (DA) neurons, the highly excitable proximal dendritic compartments (PDCs) and two Na+ -permeable leak channels, TRPC3 and NALCN, play a key role in pacemaking. However, the causal link between them is unknown. Here we report that the proximal dendritic localization of NALCN underlies pacemaking and burst firing in DA neurons. Our morphological analysis of nigral DA neurons reveals that TRPC3 is ubiquitously expressed in the whole somatodendritic compartment, but NALCN is localized within the PDCs. Blocking either TRPC3 or NALCN channels abolished pacemaking. However, only blocking NALCN, not TRPC3, degraded burst discharges. Furthermore, local glutamate uncaging readily induced burst discharges within the PDCs, compared with other parts of the neuron, and NALCN channel inhibition dissipated burst generation, indicating the importance of NALCN to the high excitability of PDCs. Therefore, we conclude that PDCs serve as a common base for tonic and burst firing in nigral DA neurons. KEY POINTS: Midbrain dopamine (DA) neurons are slow pacemakers that can generate tonic and burst firings, and the highly excitable proximal dendritic compartments (PDCs) and two Na+ -permeable leak channels, TRPC3 and NALCN, play a key role in pacemaking. We find that slow tonic firing depends on the basal activity of both the NALCN and TRPC3 channels, but that burst firing does not require TRPC3 channels but relies only on NALCN channels. We find that TRPC3 is ubiquitously expressed in the entire somatodendritic compartment, but that NALCN exists only within the PDCs in nigral DA neurons. We show that NALCN channel localization confers high excitability on PDCs and is essential for burst generation in nigral DA neurons. These results suggest that PDCs serve as a common base for tonic and burst firing in nigral DA neurons.
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Affiliation(s)
- Suyun Hahn
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Ki Bum Um
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - So Woon Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hyun Jin Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea.,Samsung Medical Center, Samsung Biomedical Research Institute, Seoul, Korea
| | - Myoung Kyu Park
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea.,Samsung Medical Center, Samsung Biomedical Research Institute, Seoul, Korea
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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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de Donato A, Buonincontri V, Borriello G, Martinelli G, Mone P. The dopamine system: insights between kidney and brain. Kidney Blood Press Res 2022; 47:493-505. [PMID: 35378538 DOI: 10.1159/000522132] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 01/21/2022] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Chronic kidney disease (CKD) is one of the most common diseases in adult age and it is typical of older adults. Recent data suggest that almost half of the elders have CKD. It is now clear that CKD is accompanied, in the early stages, by cognitive impairment, together with depression and subtle abnormalities in motor control (such as gait and balance alterations). SUMMARY Several data suggest a link between brain dopamine and kidney diseases. Metabolic syndrome and diabetes can affect dopamine neuron survival (leading to Parkinson's Disease). Several uremic toxins in CKD (uric acid, indoxyl sulphate) and trace elements accumulating in CKD (aluminium, manganese) can also modify the dopaminergic system. Hormones produced by the kidney such as vitamin D are neuroprotective for dopamine neurons. Dopaminergic drugs are useful for the treatment of a common sleep disorder in CKD, the restless legs syndrome. However, experiments on animal models of CKD show conflicting results regarding a modification of dopamine neurons. KEY MESSAGES Several observations suggest a limited relevance of the dopaminergic system in CKD-related cognitive impairment. However, a common sleep disturbance in CKD, the restless leg syndrome, improves with dopaminergic drugs. Therefore, it remains to be established the role of the dopamine system in subtle motor dysfunction observed in CKD, such as tremors, gait alterations, and central sleep apnea.
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Affiliation(s)
- Antonio de Donato
- Dipartimento di Salute Mentale, Fisica e Medicina Preventiva, Università degli Studi della Campania "Luigi Vanvitelli,", Naples, Italy
| | - Veronica Buonincontri
- Dipartimento di Salute Mentale, Fisica e Medicina Preventiva, Università degli Studi della Campania "Luigi Vanvitelli,", Naples, Italy
| | - Gianmarco Borriello
- Dipartimento di Salute Mentale, Fisica e Medicina Preventiva, Università degli Studi della Campania "Luigi Vanvitelli,", Naples, Italy
| | - Giuseppe Martinelli
- Dipartimento di Salute Mentale, Fisica e Medicina Preventiva, Università degli Studi della Campania "Luigi Vanvitelli,", Naples, Italy
- ASL Napoli, Naples, Italy
| | - Pasquale Mone
- Dipartimento di Salute Mentale, Fisica e Medicina Preventiva, Università degli Studi della Campania "Luigi Vanvitelli,", Naples, Italy
- ASL Avellino, Avellino, Italy
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11
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Lebowitz JJ, Trinkle M, Bunzow JR, Balcita-Pedicino JJ, Hetelekides S, Robinson B, De La Torre S, Aicher SA, Sesack SR, Williams JT. Subcellular localization of D2 receptors in the murine substantia nigra. Brain Struct Funct 2021; 227:925-941. [PMID: 34854963 DOI: 10.1007/s00429-021-02432-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Accepted: 11/08/2021] [Indexed: 12/13/2022]
Abstract
G-protein-coupled D2 autoreceptors expressed on dopamine neurons (D2Rs) inhibit transmitter release and cell firing at axonal endings and somatodendritic compartments. Mechanistic details of somatodendritic dopamine release remain unresolved, partly due to insufficient information on the subcellular distribution of D2Rs. Previous studies localizing D2Rs have been hindered by a dearth of antibodies validated for specificity in D2R knockout animals and have been limited by the small sampling areas imaged by electron microscopy. This study utilized sub-diffraction fluorescence microscopy and electron microscopy to examine D2 receptors in a superecliptic pHlourin GFP (SEP) epitope-tagged D2 receptor knockin mouse. Incubating live slices with an anti-SEP antibody achieved the selective labeling of plasma membrane-associated receptors for immunofluorescent imaging over a large area of the substantia nigra pars compacta (SNc). SEP-D2Rs appeared as puncta-like structures along the surface of dendrites and soma of dopamine neurons visualized by antibodies to tyrosine hydroxylase (TH). TH-associated SEP-D2Rs displayed a cell surface density of 0.66 puncta/µm2, which corresponds to an average frequency of 1 punctum every 1.50 µm. Separate ultrastructural experiments using silver-enhanced immunogold revealed that membrane-bound particles represented 28% of total D2Rs in putative dopamine cells within the SNc. Structures immediately adjacent to dendritic membrane gold particles were unmyelinated axons or axon varicosities (40%), astrocytes (19%), other dendrites (7%), or profiles unidentified (34%) in single sections. Some apposed profiles also expressed D2Rs. Fluorescent and ultrastructural analyses also provided the first visualization of membrane D2Rs at the axon initial segment, a compartment critical for action potential generation. The punctate appearance of anti-SEP staining indicates there is a population of D2Rs organized in discrete signaling sites along the plasma membrane, and for the first time, a quantitative estimate of spatial frequency is provided.
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Affiliation(s)
- Joseph J Lebowitz
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Mason Trinkle
- Departments of Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - James R Bunzow
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA
| | | | - Savas Hetelekides
- Departments of Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Brooks Robinson
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Santiago De La Torre
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Sue A Aicher
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Susan R Sesack
- Departments of Neuroscience, University of Pittsburgh, Pittsburgh, PA, 15260, USA.,Departments of Psychiatry, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - John T Williams
- Vollum Institute, Oregon Health and Science University, Portland, OR, 97239, USA.
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12
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Shao J, Liu Y, Gao D, Tu J, Yang F. Neural Burst Firing and Its Roles in Mental and Neurological Disorders. Front Cell Neurosci 2021; 15:741292. [PMID: 34646123 PMCID: PMC8502892 DOI: 10.3389/fncel.2021.741292] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 08/26/2021] [Indexed: 11/29/2022] Open
Abstract
Neural firing patterns are critical for specific information coding and transmission, and abnormal firing is implicated in a series of neural pathologies. Recent studies have indicated that enhanced burst firing mediated by T-type voltage-gated calcium channels (T-VGCCs) in specific neuronal subtypes is involved in several mental or neurological disorders such as depression and epilepsy, while suppression of T-VGCCs relieve related symptoms. Burst firing consists of groups of relatively high-frequency spikes separated by quiescence. Neurons in a variety of brain areas, including the thalamus, hypothalamus, cortex, and hippocampus, display burst firing, but the ionic mechanisms that generating burst firing and the related physiological functions vary among regions. In this review, we summarize recent findings on the mechanisms underlying burst firing in various brain areas, as well as the roles of burst firing in several mental and neurological disorders. We also discuss the ion channels and receptors that may regulate burst firing directly or indirectly, with these molecules highlighted as potential intervention targets for the treatment of mental and neurological disorders.
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Affiliation(s)
- Jie Shao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Yunhui Liu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China
| | - Dashuang Gao
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Jie Tu
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Fan Yang
- The Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, China.,Shenzhen College of Advanced Technology, University of Chinese Academy of Sciences, Beijing, China
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13
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Dos Santos AB, Skaanning LK, Mikkelsen E, Romero-Leguizamón CR, Kristensen MP, Klein AB, Thaneshwaran S, Langkilde AE, Kohlmeier KA. α-Synuclein Responses in the Laterodorsal Tegmentum, the Pedunculopontine Tegmentum, and the Substantia Nigra: Implications for Early Appearance of Sleep Disorders in Parkinson's Disease. JOURNAL OF PARKINSONS DISEASE 2021; 11:1773-1790. [PMID: 34151857 DOI: 10.3233/jpd-212554] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Parkinson's disease (PD) is a neurodegenerative disorder associated with insoluble pathological aggregates of the protein α-synuclein. While PD is diagnosed by motor symptoms putatively due to aggregated α-synuclein-mediated damage to substantia nigra (SN) neurons, up to a decade before motor symptom appearance, patients exhibit sleep disorders (SDs). Therefore, we hypothesized that α-synuclein, which can be present in monomeric, fibril, and other forms, has deleterious cellular actions on sleep-control nuclei. OBJECTIVE We investigated whether native monomer and fibril forms of α-synuclein have effects on neuronal function, calcium dynamics, and cell-death-induction in two sleep-controlling nuclei: the laterodorsal tegmentum (LDT), and the pedunculopontine tegmentum (PPT), as well as the motor-controlling SN. METHODS Size exclusion chromatography, Thioflavin T emission, and circular dichroism spectroscopy were used to isolate structurally defined forms of recombinant, human α-synuclein. Neuronal and viability effects of characterized monomeric and fibril forms of α-synuclein were determined on LDT, PPT, and SN neurons using electrophysiology, calcium imaging, and neurotoxicity assays. RESULTS In LDT and PPT, both forms of α-synuclein induced excitation and increased calcium, and the monomeric form heightened putatively excitotoxic neuronal death, whereas, in the SN we saw inhibition, decreased intracellular calcium, and monomeric α-synuclein was not associated with heightened cell death. CONCLUSION Nucleus-specific differential effects suggest mechanistic underpinnings of SDs' prodromal appearance in PD. While speculative, we hypothesize that the monomeric form of α-synuclein compromises functionality of sleep-control neurons, leading to the presence of SDs decades prior to motor dysfunction.
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Affiliation(s)
| | - Line K Skaanning
- Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Eyd Mikkelsen
- Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Anders B Klein
- Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | | | | | - Kristi A Kohlmeier
- Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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14
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Mechanism of Pacemaker Activity in Zebrafish DC2/4 Dopaminergic Neurons. J Neurosci 2021; 41:4141-4157. [PMID: 33731451 DOI: 10.1523/jneurosci.2124-20.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 02/02/2021] [Accepted: 02/07/2021] [Indexed: 11/21/2022] Open
Abstract
Zebrafish models are used increasingly to study the molecular pathogenesis of Parkinson's disease (PD), owing to the extensive array of techniques available for their experimental manipulation and analysis. The ascending dopaminergic projection from the posterior tuberculum (TPp; diencephalic populations DC2 and DC4) to the subpallium is considered the zebrafish correlate of the mammalian nigrostriatal projection, but little is known about the neurophysiology of zebrafish DC2/4 neurons. This is an important knowledge gap, because autonomous activity in mammalian substantia nigra (SNc) dopaminergic neurons contributes to their vulnerability in PD models. Using a new transgenic zebrafish line to label living dopaminergic neurons, and a novel brain slice preparation, we conducted whole-cell patch clamp recordings of DC2/4 neurons from adult zebrafish of both sexes. Zebrafish DC2/4 neurons share many physiological properties with mammalian dopaminergic neurons, including the cell-autonomous generation of action potentials. However, in contrast to mammalian dopaminergic neurons, the pacemaker driving intrinsic rhythmic activity in zebrafish DC2/4 neurons does not involve calcium conductances, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, or sodium leak currents. Instead, voltage clamp recordings and computational models show that interactions between three components - a small, predominantly potassium, leak conductance, voltage-gated sodium channels, and voltage-gated potassium channels - are sufficient for pacemaker activity in zebrafish DC2/4 neurons. These results contribute to understanding the comparative physiology of the dopaminergic system and provide a conceptual basis for interpreting data derived from zebrafish PD models. The findings further suggest new experimental opportunities to address the role of dopaminergic pacemaker activity in the pathogenesis of PD.SIGNIFICANCE STATEMENT Posterior tuberculum (TPp) DC2/4 dopaminergic neurons are considered the zebrafish correlate of mammalian substantia nigra (SNc) neurons, whose degeneration causes the motor signs of Parkinson's disease (PD). Our study shows that DC2/4 and SNc neurons share a number of electrophysiological properties, including depolarized membrane potential, high input resistance, and continual, cell-autonomous pacemaker activity, that strengthen the basis for the increasing use of zebrafish models to study the molecular pathogenesis of PD. The mechanisms driving pacemaker activity differ between DC2/4 and SNc neurons, providing: (1) experimental opportunities to dissociate the contributions of intrinsic activity and underlying pacemaker currents to pathogenesis; and (2) essential information for the design and interpretation of studies using zebrafish PD models.
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15
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Hikima T, Lee CR, Witkovsky P, Chesler J, Ichtchenko K, Rice ME. Activity-dependent somatodendritic dopamine release in the substantia nigra autoinhibits the releasing neuron. Cell Rep 2021; 35:108951. [PMID: 33826884 PMCID: PMC8189326 DOI: 10.1016/j.celrep.2021.108951] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/20/2020] [Accepted: 03/15/2021] [Indexed: 12/12/2022] Open
Abstract
Somatodendritic dopamine (DA) release from midbrain DA neurons activates D2 autoreceptors on these cells to regulate their activity. However, the source of autoregulatory DA remains controversial. Here, we test the hypothesis that D2 autoreceptors on a given DA neuron in the substantia nigra pars compacta (SNc) are activated primarily by DA released from that same cell, rather than from its neighbors. Voltage-clamp recording allows monitoring of evoked D2-receptor-mediated inhibitory currents (D2ICs) in SNc DA neurons as an index of DA release. Single-cell application of antibodies to Na+ channels via the recording pipette decreases spontaneous activity of recorded neurons and attenuates evoked D2ICs; antibodies to SNAP-25, a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein, also decrease D2IC amplitude. Evoked D2ICs are nearly abolished by the light chain of botulinum neurotoxin A, which cleaves SNAP-25, whereas synaptically activated GABAB-receptor-mediated currents are unaffected. Thus, somatodendritic DA release in the SNc autoinhibits the neuron that releases it.
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Affiliation(s)
- Takuya Hikima
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Christian R Lee
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Paul Witkovsky
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Julia Chesler
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Konstantin Ichtchenko
- Department of Biochemistry & Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Margaret E Rice
- Department of Neurosurgery, New York University Grossman School of Medicine, New York, NY 10016, USA; Department of Neuroscience & Physiology, New York University Grossman School of Medicine, New York, NY 10016, USA.
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16
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López‐Gambero AJ, Rodríguez de Fonseca F, Suárez J. Energy sensors in drug addiction: A potential therapeutic target. Addict Biol 2021; 26:e12936. [PMID: 32638485 DOI: 10.1111/adb.12936] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 06/10/2020] [Accepted: 06/15/2020] [Indexed: 01/05/2023]
Abstract
Addiction is defined as the repeated exposure and compulsive seek of psychotropic drugs that, despite the harmful effects, generate relapse after the abstinence period. The psychophysiological processes associated with drug addiction (acquisition/expression, withdrawal, and relapse) imply important alterations in neurotransmission and changes in presynaptic and postsynaptic plasticity and cellular structure (neuroadaptations) in neurons of the reward circuits (dopaminergic neuronal activity) and other corticolimbic regions. These neuroadaptation mechanisms imply important changes in neuronal energy balance and protein synthesis machinery. Scientific literature links drug-induced stimulation of dopaminergic and glutamatergic pathways along with presence of neurotrophic factors with alterations in synaptic plasticity and membrane excitability driven by metabolic sensors. Here, we provide current knowledge of the role of molecular targets that constitute true metabolic/energy sensors such as AMPK, mTOR, ERK, or KATP in the development of the different phases of addiction standing out the main brain regions (ventral tegmental area, nucleus accumbens, hippocampus, and amygdala) constituting the hubs in the development of addiction. Because the available treatments show very limited effectiveness, evaluating the drug efficacy of AMPK and mTOR specific modulators opens up the possibility of testing novel pharmacotherapies for an individualized approach in drug abuse.
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Affiliation(s)
- Antonio Jesús López‐Gambero
- Instituto de Investigación Biomédica de Málaga (IBIMA), Hospital Regional Universitario de Málaga Universidad de Málaga Málaga Spain
| | - Fernando Rodríguez de Fonseca
- Instituto de Investigación Biomédica de Málaga (IBIMA), UGC Salud Mental Hospital Regional Universitario de Málaga Málaga Spain
| | - Juan Suárez
- Instituto de Investigación Biomédica de Málaga (IBIMA), UGC Salud Mental Hospital Regional Universitario de Málaga Málaga Spain
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17
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Chaunsali L, Tewari BP, Gallucci A, Thompson EG, Savoia A, Feld N, Campbell SL. Glioma-induced peritumoral hyperexcitability in a pediatric glioma model. Physiol Rep 2020; 8:e14567. [PMID: 33026196 PMCID: PMC7539466 DOI: 10.14814/phy2.14567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/10/2020] [Accepted: 08/10/2020] [Indexed: 11/24/2022] Open
Abstract
Epileptic seizures are among the most common presenting symptom in patients with glioma. The etiology of glioma-related seizures is complex and not completely understood. Studies using adult glioma patient tissue and adult glioma mouse models, show that neurons adjacent to the tumor mass, peritumoral neurons, are hyperexcitable and contribute to seizures. Although it is established that there are phenotypic and genotypic distinctions in gliomas from adult and pediatric patients, it is unknown whether these established differences in pediatric glioma biology and the microenvironment in which these glioma cells harbor, the developing brain, differentially impacts surrounding neurons. In the present study, we examine the effect of patient-derived pediatric glioma cells on the function of peritumoral neurons using two pediatric glioma models. Pediatric glioma cells were intracranially injected into the cerebrum of postnatal days 2 and 3 (p2/3) mouse pups for 7 days. Electrophysiological recordings showed that cortical layer 2/3 peritumoral neurons exhibited significant differences in their intrinsic properties compared to those of sham control neurons. Peritumoral neurons fired significantly more action potentials in response to smaller current injection and exhibited a depolarization block in response to higher current injection. The threshold for eliciting an action potential and pharmacologically induced epileptiform activity was lower in peritumoral neurons compared to sham. Our findings suggest that pediatric glioma cells increase excitability in the developing peritumoral neurons by exhibiting early onset of depolarization block, which was not previously observed in adult glioma peritumoral neurons.
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Affiliation(s)
- Lata Chaunsali
- Molecular and Cellular Biology Graduate ProgramSchool of NeuroscienceVirginia TechBlacksburgVAUSA
| | - Bhanu P. Tewari
- Fralin Biomedical Research InstituteGlial Biology in HealthDisease and CancerVirginia TechRoanokeVAUSA
| | - Allison Gallucci
- Fralin Biomedical Research InstituteTranslational Biology, Medicine and HealthVirginia TechRoanokeVAUSA
| | | | - Andrew Savoia
- Animal and Poultry SciencesVirginia TechBlacksburgVAUSA
| | - Noah Feld
- School of MedicineVirginia Commonwealth UniversityRichmondVAUSA
| | - Susan L. Campbell
- Molecular and Cellular Biology Graduate ProgramSchool of NeuroscienceVirginia TechBlacksburgVAUSA
- Fralin Biomedical Research InstituteGlial Biology in HealthDisease and CancerVirginia TechRoanokeVAUSA
- Animal and Poultry SciencesVirginia TechBlacksburgVAUSA
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18
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Goaillard JM, Moubarak E, Tapia M, Tell F. Diversity of Axonal and Dendritic Contributions to Neuronal Output. Front Cell Neurosci 2020; 13:570. [PMID: 32038171 PMCID: PMC6987044 DOI: 10.3389/fncel.2019.00570] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 12/09/2019] [Indexed: 11/13/2022] Open
Abstract
Our general understanding of neuronal function is that dendrites receive information that is transmitted to the axon, where action potentials (APs) are initiated and propagated to eventually trigger neurotransmitter release at synaptic terminals. Even though this canonical division of labor is true for a number of neuronal types in the mammalian brain (including neocortical and hippocampal pyramidal neurons or cerebellar Purkinje neurons), many neuronal types do not comply with this classical polarity scheme. In fact, dendrites can be the site of AP initiation and propagation, and even neurotransmitter release. In several interneuron types, all functions are carried out by dendrites as these neurons are devoid of a canonical axon. In this article, we present a few examples of "misbehaving" neurons (with a non-canonical polarity scheme) to highlight the diversity of solutions that are used by mammalian neurons to transmit information. Moreover, we discuss how the contribution of dendrites and axons to neuronal excitability may impose constraints on the morphology of these compartments in specific functional contexts.
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Affiliation(s)
- Jean-Marc Goaillard
- UMR_S 1072, Aix Marseille Université, INSERM, Faculté de Médecine Secteur Nord, Marseille, France
| | - Estelle Moubarak
- UMR_S 1072, Aix Marseille Université, INSERM, Faculté de Médecine Secteur Nord, Marseille, France
| | - Mónica Tapia
- UMR_S 1072, Aix Marseille Université, INSERM, Faculté de Médecine Secteur Nord, Marseille, France
| | - Fabien Tell
- UMR_S 1072, Aix Marseille Université, INSERM, Faculté de Médecine Secteur Nord, Marseille, France
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20
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Rumbell T, Kozloski J. Dimensions of control for subthreshold oscillations and spontaneous firing in dopamine neurons. PLoS Comput Biol 2019; 15:e1007375. [PMID: 31545787 PMCID: PMC6776370 DOI: 10.1371/journal.pcbi.1007375] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 10/03/2019] [Accepted: 09/04/2019] [Indexed: 11/20/2022] Open
Abstract
Dopaminergic neurons (DAs) of the rodent substantia nigra pars compacta (SNc) display varied electrophysiological properties in vitro. Despite this, projection patterns and functional inputs from DAs to other structures are conserved, so in vivo delivery of consistent, well-timed dopamine modulation to downstream circuits must be coordinated. Here we show robust coordination by linear parameter controllers, discovered through powerful mathematical analyses of data and models, and from which consistent control of DA subthreshold oscillations (STOs) and spontaneous firing emerges. These units of control represent coordinated intracellular variables, sufficient to regulate complex cellular properties with radical simplicity. Using an evolutionary algorithm and dimensionality reduction, we discovered metaparameters, which when regressed against STO features, revealed a 2-dimensional control plane for the neuron’s 22-dimensional parameter space that fully maps the natural range of DA subthreshold electrophysiology. This plane provided a basis for spiking currents to reproduce a large range of the naturally occurring spontaneous firing characteristics of SNc DAs. From it we easily produced a unique population of models, derived using unbiased parameter search, that show good generalization to channel blockade and compensatory intracellular mechanisms. From this population of models, we then discovered low-dimensional controllers for regulating spontaneous firing properties, and gain insight into how currents active in different voltage regimes interact to produce the emergent activity of SNc DAs. Our methods therefore reveal simple regulators of neuronal function lurking in the complexity of combined ion channel dynamics. Electrophysiological activity of the neuronal membrane and concomitant ion channel properties are highly variable within groups of neurons of the same type from the same brain region. Reconciliation of the mechanisms generating neuronal activity is challenging due to the complexity of the interactions between the channel currents involved. Here we present a set of mathematical analyses that uncover the low-dimensional intracellular parameter combinations capable of regulating features of subthreshold oscillations and spontaneous firing in empirically constrained models of nigral dopaminergic neurons. This method generates, from a naive starting point, linear combinations of ion channel properties that are surprisingly capable of reliably controlling a wide variety of emergent electrophysiological activity, thereby predicting drug effects and shedding light on unsuspected compensatory mechanisms that contribute to neuronal function.
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Affiliation(s)
- Timothy Rumbell
- IBM Research, Computational Biology Center, Thomas J. Watson Research Laboratories, Yorktown Heights, New York, United States of America
- * E-mail:
| | - James Kozloski
- IBM Research, Computational Biology Center, Thomas J. Watson Research Laboratories, Yorktown Heights, New York, United States of America
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21
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Trpc5 deficiency causes hypoprolactinemia and altered function of oscillatory dopamine neurons in the arcuate nucleus. Proc Natl Acad Sci U S A 2019; 116:15236-15243. [PMID: 31285329 DOI: 10.1073/pnas.1905705116] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Dopamine neurons of the hypothalamic arcuate nucleus (ARC) tonically inhibit the release of the protein hormone prolactin from lactotropic cells in the anterior pituitary gland and thus play a central role in prolactin homeostasis of the body. Prolactin, in turn, orchestrates numerous important biological functions such as maternal behavior, reproduction, and sexual arousal. Here, we identify the canonical transient receptor potential channel Trpc5 as an essential requirement for normal function of dopamine ARC neurons and prolactin homeostasis. By analyzing female mice carrying targeted mutations in the Trpc5 gene including a conditional Trpc5 deletion, we show that Trpc5 is required for maintaining highly stereotyped infraslow membrane potential oscillations of dopamine ARC neurons. Trpc5 is also required for eliciting prolactin-evoked tonic plateau potentials in these neurons that are part of a regulatory feedback circuit. Trpc5 mutant females show severe prolactin deficiency or hypoprolactinemia that is associated with irregular reproductive cyclicity, gonadotropin imbalance, and impaired reproductive capabilities. These results reveal a previously unknown role for the cation channel Trpc5 in prolactin homeostasis of female mice and provide strategies to explore the genetic basis of reproductive disorders and other malfunctions associated with defective prolactin regulation in humans.
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22
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Robustness to Axon Initial Segment Variation Is Explained by Somatodendritic Excitability in Rat Substantia Nigra Dopaminergic Neurons. J Neurosci 2019; 39:5044-5063. [PMID: 31028116 DOI: 10.1523/jneurosci.2781-18.2019] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 03/27/2019] [Accepted: 03/27/2019] [Indexed: 01/12/2023] Open
Abstract
In many neuronal types, axon initial segment (AIS) geometry critically influences neuronal excitability. Interestingly, the axon of rat SNc dopaminergic (DA) neurons displays a highly variable location and most often arises from an axon-bearing dendrite (ABD). We combined current-clamp somatic and dendritic recordings, outside-out recordings of dendritic sodium and potassium currents, morphological reconstructions and multicompartment modeling on male and female rat SNc DA neurons to determine cell-to-cell variations in AIS and ABD geometry, and their influence on neuronal output (spontaneous pacemaking frequency, action potential [AP] shape). Both AIS and ABD geometries were found to be highly variable from neuron to neuron. Surprisingly, we found that AP shape and pacemaking frequency were independent of AIS geometry. Modeling realistic morphological and biophysical variations helped us clarify this result: in SNc DA neurons, the complexity of the ABD combined with its excitability predominantly define pacemaking frequency and AP shape, such that large variations in AIS geometry negligibly affect neuronal output and are tolerated.SIGNIFICANCE STATEMENT In many neuronal types, axon initial segment (AIS) geometry critically influences neuronal excitability. In the current study, we describe large cell-to-cell variations in AIS length or distance from the soma in rat substantia nigra pars compacta dopaminergic neurons. Using neuronal reconstruction and electrophysiological recordings, we show that this morphological variability does not seem to affect their electrophysiological output, as neither action potential properties nor pacemaking frequency is correlated with AIS morphology. Realistic multicompartment modeling suggests that this robustness to AIS variation is mainly explained by the complexity and excitability of the somatodendritic compartment.
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23
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Dopamine neuron-derived IGF-1 controls dopamine neuron firing, skill learning, and exploration. Proc Natl Acad Sci U S A 2019; 116:3817-3826. [PMID: 30808767 PMCID: PMC6397563 DOI: 10.1073/pnas.1806820116] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Midbrain dopamine neurons play a role in motivational and cognitive control of behavior. In addition, they regulate motor functions. Dysregulation of dopamine neurons has been linked to depression, schizophrenia, and addiction and their degeneration is causal to Parkinson’s disease. Peripheral hormones have been shown to regulate dopamine neurons functions. Insulin-like growth factor 1 (IGF-1) is a hormone mainly produced in the liver. With this study we discovered that midbrain dopamine neurons synthesize and release IGF-1 in an activity dependent manner. In addition, dopamine neuron-derived IGF-1 modulates dopamine synthesis and dopamine neuron firing and ultimately it controls dopamine-dependent behaviors. This study highlights the neuromodulatory role of neuron-derived IGF-1 and its role in shaping dopamine transmission in the brain. Midbrain dopamine neurons, which can be regulated by neuropeptides and hormones, play a fundamental role in controlling cognitive processes, reward mechanisms, and motor functions. The hormonal actions of insulin-like growth factor 1 (IGF-1) produced by the liver have been well described, but the role of neuronally derived IGF-1 remains largely unexplored. We discovered that dopamine neurons secrete IGF-1 from the cell bodies following depolarization, and that IGF-1 controls release of dopamine in the ventral midbrain. In addition, conditional deletion of dopamine neuron-derived IGF-1 in adult mice leads to decrease of dopamine content in the striatum and deficits in dopamine neuron firing and causes reduced spontaneous locomotion and impairments in explorative and learning behaviors. These data identify that dopamine neuron-derived IGF-1 acts as a regulator of dopamine neurons and regulates dopamine-mediated behaviors.
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Liss B, Striessnig J. The Potential of L-Type Calcium Channels as a Drug Target for Neuroprotective Therapy in Parkinson's Disease. Annu Rev Pharmacol Toxicol 2019; 59:263-289. [PMID: 30625283 DOI: 10.1146/annurev-pharmtox-010818-021214] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The motor symptoms of Parkinson's disease (PD) mainly arise from degeneration of dopamine neurons within the substantia nigra. As no disease-modifying PD therapies are available, and side effects limit long-term benefits of current symptomatic therapies, novel treatment approaches are needed. The ongoing phase III clinical study STEADY-PD is investigating the potential of the dihydropyridine isradipine, an L-type Ca2+ channel (LTCC) blocker, for neuroprotective PD therapy. Here we review the clinical and preclinical rationale for this trial and discuss potential reasons for the ambiguous outcomes of in vivo animal model studies that address PD-protective dihydropyridine effects. We summarize current views about the roles of Cav1.2 and Cav1.3 LTCC isoforms for substantia nigra neuron function, and their high vulnerability to degenerative stressors, and for PD pathophysiology. We discuss different dihydropyridine sensitivities of LTCC isoforms in view of their potential as drug targets for PD neuroprotection, and we conclude by considering how these aspects could guide further drug development.
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Affiliation(s)
- Birgit Liss
- Institut für Angewandte Physiologie, Universität Ulm, 89081 Ulm, Germany;
| | - Jörg Striessnig
- Abteilung Pharmakologie und Toxikologie, Institut für Pharmazie, and Center for Molecular Biosciences Innsbruck, Universität Innsbruck, A-6020 Innsbruck, Austria;
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Philippart F, Khaliq ZM. G i/o protein-coupled receptors in dopamine neurons inhibit the sodium leak channel NALCN. eLife 2018; 7:40984. [PMID: 30556810 PMCID: PMC6305199 DOI: 10.7554/elife.40984] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/17/2018] [Indexed: 12/13/2022] Open
Abstract
Dopamine (D2) receptors provide autoinhibitory feedback onto dopamine neurons through well-known interactions with voltage-gated calcium channels and G protein-coupled inwardly-rectifying potassium (GIRK) channels. Here, we reveal a third major effector involved in D2R modulation of dopaminergic neurons - the sodium leak channel, NALCN. We found that activation of D2 receptors robustly inhibits isolated sodium leak currents in wild-type mice but not in NALCN conditional knockout mice. Intracellular GDP-βS abolished the inhibition, indicating a G protein-dependent signaling mechanism. The application of dopamine reliably slowed pacemaking even when GIRK channels were pharmacologically blocked. Furthermore, while spontaneous activity was observed in nearly all dopaminergic neurons in wild-type mice, neurons from NALCN knockouts were mainly silent. Both observations demonstrate the critical importance of NALCN for pacemaking in dopaminergic neurons. Finally, we show that GABA-B receptor activation also produces inhibition of NALCN-mediated currents. Therefore, we identify NALCN as a core effector of inhibitory G protein-coupled receptors.
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Affiliation(s)
- Fabian Philippart
- Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Maryland, United States
| | - Zayd M Khaliq
- Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Maryland, United States
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Lynch WB, Tschumi CW, Sharpe AL, Branch SY, Chen C, Ge G, Li S, Beckstead MJ. Progressively disrupted somatodendritic morphology in dopamine neurons in a mouse Parkinson's model. Mov Disord 2018; 33:1928-1937. [PMID: 30440089 DOI: 10.1002/mds.27541] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 08/10/2018] [Accepted: 09/16/2018] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Parkinson's disease is characterized by the progressive loss of dopamine neurons in the substantia nigra, leading to severe motor deficits. Although the disease likely begins to develop years before observable motor symptoms, the specific morphological and functional alterations involved are poorly understood. OBJECTIVES MitoPark mice lack the gene coding for mitochondrial transcription factor A specifically in dopamine neurons, which over time produces a progressive decline of neuronal function and related behavior that phenotypically mirrors human parkinsonism. Our previous work identified a progressive decrease in cell capacitance in dopamine neurons from MitoPark mice, possibly suggesting reduced membrane surface area. We therefore sought to identify and quantify somatodendritic parameters in this model across age. METHODS We used whole-cell patch clamp and fluorescent labeling to quantify somatodendritic morphology of single, neurobiotin-filled dopamine neurons in acutely isolated brain slices from MitoPark mice. RESULTS We found that MitoPark mice exhibit an adult-onset, age-dependent reduction of neuritic branching and soma size in dopamine neurons. This decline proceeds similarly in MitoPark mice of both sexes, but does not begin until after the age that early decrements in ion channel physiology and behavior have previously been observed. CONCLUSIONS A progressive and severe decline in somatodendritic morphology occurs prior to cell death, but is not responsible for the subtle decrements observable in the earliest stages of neurodegeneration. This work could help identify the ideal time window for specific treatments to halt disease progression and avert debilitating motor deficits in Parkinson's patients. © 2018 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- William B Lynch
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA
| | - Christopher W Tschumi
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Department of Cellular and Integrative Physiology, University of Texas Health, San Antonio, Texas, USA
| | - Amanda L Sharpe
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Department of Pharmaceutical Sciences, University of Oklahoma College of Pharmacy, Oklahoma City, Oklahoma, USA
| | - Sarah Y Branch
- Department of Cellular and Integrative Physiology, University of Texas Health, San Antonio, Texas, USA
| | - Cang Chen
- Department of Medicine, University of Texas Health, San Antonio, Texas, USA
| | - Guo Ge
- Department of Medicine, University of Texas Health, San Antonio, Texas, USA
| | - Senlin Li
- Department of Medicine, University of Texas Health, San Antonio, Texas, USA
| | - Michael J Beckstead
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, USA.,Department of Cellular and Integrative Physiology, University of Texas Health, San Antonio, Texas, USA
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27
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Yang S, Wang J, Lin Q, Deng B, Wei X, Liu C, Li H. Cost-efficient FPGA implementation of a biologically plausible dopamine neural network and its application. Neurocomputing 2018. [DOI: 10.1016/j.neucom.2018.07.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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di Volo M, Morozova EO, Lapish CC, Kuznetsov A, Gutkin B. Dynamical ventral tegmental area circuit mechanisms of alcohol-dependent dopamine release. Eur J Neurosci 2018; 50:2282-2296. [PMID: 30215874 DOI: 10.1111/ejn.14147] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 08/15/2018] [Accepted: 08/24/2018] [Indexed: 11/28/2022]
Abstract
A large body of data has identified numerous molecular targets through which ethanol (EtOH) acts on brain circuits. Yet how these multiple mechanisms interact to result in dysregulated dopamine (DA) release under the influence of alcohol in vivo remains unclear. In this manuscript, we delineate potential circuit-level mechanisms responsible for EtOH-dependent dysregulation of DA release from the ventral tegmental area (VTA) into its projection areas. For this purpose, we constructed a circuit model of the VTA that integrates realistic Glutamatergic (Glu) inputs and reproduces DA release observed experimentally. We modelled the concentration-dependent effects of EtOH on its principal VTA targets. We calibrated the model to reproduce the inverted U-shape dose dependence of DA neuron activity on EtOH concentration. The model suggests a primary role of EtOH-induced boost in the Ih and AMPA currents in the DA firing-rate/bursting increase. This is counteracted by potentiated GABA transmission that decreases DA neuron activity at higher EtOH concentrations. Thus, the model connects well-established in vitro pharmacological EtOH targets with its in vivo influence on neuronal activity. Furthermore, we predict that increases in VTA activity produced by moderate EtOH doses require partial synchrony and relatively low rates of the Glu afferents. We propose that the increased frequency of transient (phasic) DA peaks evoked by EtOH results from synchronous population bursts in VTA DA neurons. Our model predicts that the impact of acute ETOH on dopamine release is critically shaped by the structure of the cortical inputs to the VTA.
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Affiliation(s)
- Matteo di Volo
- Unité de Neurosciences, Information et Complexité, CNRS, Gif-sur-Yvette, France.,Group for Neural Theory, LNC INSERM U960, DEC Ecole Normale Superieure PSL University, Paris, France
| | | | - Christopher C Lapish
- Addiction Neuroscience Program, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Alexey Kuznetsov
- Department of Mathematical Sciences, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Boris Gutkin
- Group for Neural Theory, LNC INSERM U960, DEC Ecole Normale Superieure PSL University, Paris, France.,Center for Cognition and Decision Making, NRU HSE, Moscow, Russia
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Morphological and Biophysical Determinants of the Intracellular and Extracellular Waveforms in Nigral Dopaminergic Neurons: A Computational Study. J Neurosci 2018; 38:8295-8310. [PMID: 30104340 DOI: 10.1523/jneurosci.0651-18.2018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 07/12/2018] [Accepted: 08/09/2018] [Indexed: 11/21/2022] Open
Abstract
Action potentials (APs) in nigral dopaminergic neurons often exhibit two separate components: the first reflecting spike initiation in the dendritically located axon initial segment (AIS) and the second the subsequent dendro-somatic spike. These components are separated by a notch in the ascending phase of the somatic extracellular waveform and in the temporal derivative of the somatic intracellular waveform. Still, considerable variability exists in the presence and magnitude of the notch across neurons. To systematically address the contribution of AIS, dendritic and somatic compartments to shaping the two-component APs, we modeled APs of previously in vivo electrophysiologically characterized and 3D-reconstructed male mouse and rat dopaminergic neurons. A parsimonious two-domain model, with high (AIS) and lower (dendro-somatic) Na+ conductance, reproduced the notch in the temporal derivatives, but not in the extracellular APs, regardless of morphology. The notch was only revealed when somatic active currents were reduced, constraining the model to three domains. Thus, an initial AIS spike is followed by an actively generated spike by the axon-bearing dendrite (ABD), in turn followed mostly passively by the soma. The transition from being a source compartment for the AIS spike to a source compartment for the ABD spike satisfactorily explains the extracellular somatic notch. Larger AISs and thinner ABD (but not soma-to-AIS distance) accentuate the AIS component. We conclude that variability in AIS size and ABD caliber explains variability in AP extracellular waveform and separation of AIS and dendro-somatic components, given the presence of at least three functional domains with distinct excitability characteristics.SIGNIFICANCE STATEMENT Midbrain dopamine neurons make an important contribution to circuits mediating motivation and movement. Understanding the basic rules that govern the electrical activity of single dopaminergic neurons is therefore essential to reveal how they ultimately contribute to movement and motivation as well as what goes wrong in associated disorders. Our computational study focuses on the generation and propagation of action potentials and shows that different morphologies and excitability characteristics of the cell body, dendrites and proximal axon can explain the diversity of action potentials shapes in this population. These compartments likely make differential contributions both to normal dopaminergic signaling and could potentially underlie pathological dopaminergic signaling implicated in addiction, schizophrenia, Parkinson's disease, and other disorders.
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31
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Rourk CJ. Ferritin and neuromelanin "quantum dot" array structures in dopamine neurons of the substantia nigra pars compacta and norepinephrine neurons of the locus coeruleus. Biosystems 2018; 171:48-58. [PMID: 30048795 DOI: 10.1016/j.biosystems.2018.07.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/13/2018] [Accepted: 07/22/2018] [Indexed: 01/28/2023]
Abstract
In this review, the author shows that ferritin has documented quantum dot material properties that have been reported in numerous independent studies, and can enable quantum mechanical electron transport over substantial distances. In addition, neuromelanin is a pi-conjugated polymer, and quantum dot/pi-conjugated polymer combinations have been reported in numerous independent studies to facilitate electron transport for solar photovoltaic and other applications. Both ferritin and neuromelanin are present in large quantities in the dopamine neurons of the substantia nigra pars compactaand the norepinephrine neurons of the locus coeruleus. The unique structure of subgroups of these neurons that have a large number of axon branches and synapses may have evolved to take advantage of this electron transport mechanism, if it is present, such as to coordinate conscious action, or for other purposes. Independent clinical and laboratory studies are also reviewed that corroborate this theory of coordinated action in these neuron groups. Research to validate the theory using charge transport measurements, materials characterization, existing fluorescent probe material and reaction time testing is proposed.
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32
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Sequential Application of Discrete Topographical Patterns Enhances Derivation of Functional Mesencephalic Dopaminergic Neurons from Human Induced Pluripotent Stem Cells. Sci Rep 2018; 8:9567. [PMID: 29934644 PMCID: PMC6014983 DOI: 10.1038/s41598-018-27653-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 06/04/2018] [Indexed: 01/07/2023] Open
Abstract
Parkinson’s Disease is a progressive neurodegenerative disorder attributed to death of mesencephalic dopaminergic (DA) neurons. Pluripotent stem cells have great potential in the study for this late-onset disease, but acquirement of cells that are robust in quantity and quality is still technically demanding. Biophysical cues have been shown to direct stem cell fate, but the effect of different topographies in the lineage commitment and subsequent maturation stages of cells have been less examined. Using human induced pluripotent stem cells (iPSCs), we applied topographical patterns sequentially during differentiation stages and examined their ability to influence derivation yield and functionality of regionalized subtype-specific DA neurons. Gratings showed higher yield of DA neurons and may be beneficial for initial lineage commitment. Cells derived on pillars in the terminal differentiation stage have increased neuronal complexity, and were more capable of firing repetitive action potentials, showing that pillars yielded better network formation and functionality. Our topography platform can be applied to patient-derived iPSCs as well, and that cells harbouring LRRK2 mutation were more functionally mature when optimal topographies were applied sequentially. This will hopefully accelerate development of robust cell models that will provide novel insights into discovering new therapeutic approaches for Parkinson’s Disease.
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33
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Gantz SC, Ford CP, Morikawa H, Williams JT. The Evolving Understanding of Dopamine Neurons in the Substantia Nigra and Ventral Tegmental Area. Annu Rev Physiol 2018; 80:219-241. [PMID: 28938084 DOI: 10.1146/annurev-physiol-021317-121615] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In recent years, the population of neurons in the ventral tegmental area (VTA) and substantia nigra (SN) has been examined at multiple levels. The results indicate that the projections, neurochemistry, and receptor and ion channel expression in this cell population vary widely. This review centers on the intrinsic properties and synaptic regulation that control the activity of dopamine neurons. Although all dopamine neurons fire action potentials in a pacemaker pattern in the absence of synaptic input, the intrinsic properties that underlie this activity differ considerably. Likewise, the transition into a burst/pause pattern results from combinations of intrinsic ion conductances, inhibitory and excitatory synaptic inputs that differ among this cell population. Finally, synaptic plasticity is a key regulator of the rate and pattern of activity in different groups of dopamine neurons. Through these fundamental properties, the activity of dopamine neurons is regulated and underlies the wide-ranging functions that have been attributed to dopamine.
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Affiliation(s)
- Stephanie C Gantz
- Intramural Research Program, National Institute on Drug Abuse, Baltimore, Maryland 21224, USA
| | - Christopher P Ford
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA
| | - Hitoshi Morikawa
- Department of Neuroscience and Waggoner Center for Alcohol and Addiction Research, University of Texas, Austin, Texas 78712, USA
| | - John T Williams
- Vollum Institute, Oregon Health Sciences University, Portland, Oregon 97239, USA;
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Role of the Axon Initial Segment in the Control of Spontaneous Frequency of Nigral Dopaminergic Neurons In Vivo. J Neurosci 2017; 38:733-744. [PMID: 29217687 DOI: 10.1523/jneurosci.1432-17.2017] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 10/24/2017] [Accepted: 11/20/2017] [Indexed: 11/21/2022] Open
Abstract
The spontaneous tonic discharge activity of nigral dopamine neurons plays a fundamental role in dopaminergic signaling. To investigate the role of neuronal morphology and architecture with respect to spontaneous activity in this population, we visualized the 3D structure of the axon initial segment (AIS) along with the entire somatodendritic domain of adult male mouse dopaminergic neurons, previously recorded in vivo We observed a positive correlation of the firing rate with both proximity and size of the AIS. Computational modeling showed that the size of the AIS, but not its position within the somatodendritic domain, is the major causal determinant of the tonic firing rate in the intact model, by virtue of the higher intrinsic frequency of the isolated AIS. Further mechanistic analysis of the relationship between neuronal morphology and firing rate showed that dopaminergic neurons function as a coupled oscillator whose frequency of discharge results from a compromise between AIS and somatodendritic oscillators. Thus, morphology plays a critical role in setting the basal tonic firing rate, which in turn could control striatal dopaminergic signaling that mediates motivation and movement.SIGNIFICANCE STATEMENT The frequency at which nigral dopamine neurons discharge action potentials sets baseline dopamine levels in the brain, which enables activity in motor, cognitive, and motivational systems. Here, we demonstrate that the size of the axon initial segment, a subcellular compartment responsible for initiating action potentials, is a key determinant of the firing rate in these neurons. The axon initial segment and all the molecular components that underlie its critical function may provide a novel target for the regulation of dopamine levels in the brain.
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TGF-β Signaling in Dopaminergic Neurons Regulates Dendritic Growth, Excitatory-Inhibitory Synaptic Balance, and Reversal Learning. Cell Rep 2017; 17:3233-3245. [PMID: 28009292 DOI: 10.1016/j.celrep.2016.11.068] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 09/26/2016] [Accepted: 11/22/2016] [Indexed: 12/21/2022] Open
Abstract
Neural circuits involving midbrain dopaminergic (DA) neurons regulate reward and goal-directed behaviors. Although local GABAergic input is known to modulate DA circuits, the mechanism that controls excitatory/inhibitory synaptic balance in DA neurons remains unclear. Here, we show that DA neurons use autocrine transforming growth factor β (TGF-β) signaling to promote the growth of axons and dendrites. Surprisingly, removing TGF-β type II receptor in DA neurons also disrupts the balance in TGF-β1 expression in DA neurons and neighboring GABAergic neurons, which increases inhibitory input, reduces excitatory synaptic input, and alters phasic firing patterns in DA neurons. Mice lacking TGF-β signaling in DA neurons are hyperactive and exhibit inflexibility in relinquishing learned behaviors and re-establishing new stimulus-reward associations. These results support a role for TGF-β in regulating the delicate balance of excitatory/inhibitory synaptic input in local microcircuits involving DA and GABAergic neurons and its potential contributions to neuropsychiatric disorders.
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36
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Galtieri DJ, Estep CM, Wokosin DL, Traynelis S, Surmeier DJ. Pedunculopontine glutamatergic neurons control spike patterning in substantia nigra dopaminergic neurons. eLife 2017; 6:30352. [PMID: 28980939 PMCID: PMC5643088 DOI: 10.7554/elife.30352] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/04/2017] [Indexed: 12/26/2022] Open
Abstract
Burst spiking in substantia nigra pars compacta (SNc) dopaminergic neurons is a key signaling event in the circuitry controlling goal-directed behavior. It is widely believed that this spiking mode depends upon an interaction between synaptic activation of N-methyl-D-aspartate receptors (NMDARs) and intrinsic oscillatory mechanisms. However, the role of specific neural networks in burst generation has not been defined. To begin filling this gap, SNc glutamatergic synapses arising from pedunculopotine nucleus (PPN) neurons were characterized using optical and electrophysiological approaches. These synapses were localized exclusively on the soma and proximal dendrites, placing them in a good location to influence spike generation. Indeed, optogenetic stimulation of PPN axons reliably evoked spiking in SNc dopaminergic neurons. Moreover, burst stimulation of PPN axons was faithfully followed, even in the presence of NMDAR antagonists. Thus, PPN-evoked burst spiking of SNc dopaminergic neurons in vivo may not only be extrinsically triggered, but extrinsically patterned as well.
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Affiliation(s)
- Daniel J Galtieri
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Chad M Estep
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - David L Wokosin
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
| | - Stephen Traynelis
- Department of Pharmacology, Emory University, Atlanta, United States
| | - D James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, United States
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González-Cabrera C, Meza R, Ulloa L, Merino-Sepúlveda P, Luco V, Sanhueza A, Oñate-Ponce A, Bolam JP, Henny P. Characterization of the axon initial segment of mice substantia nigra dopaminergic neurons. J Comp Neurol 2017; 525:3529-3542. [PMID: 28734032 DOI: 10.1002/cne.24288] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 07/08/2017] [Accepted: 07/10/2017] [Indexed: 12/11/2022]
Abstract
The axon initial segment (AIS) is the site of initiation of action potentials and influences action potential waveform, firing pattern, and rate. In view of the fundamental aspects of motor function and behavior that depend on the firing of substantia nigra pars compacta (SNc) dopaminergic neurons, we identified and characterized their AIS in the mouse. Immunostaining for tyrosine hydroxylase (TH), sodium channels (Nav ) and ankyrin-G (Ank-G) was used to visualize the AIS of dopaminergic neurons. Reconstructions of sampled AIS of dopaminergic neurons revealed variable lengths (12-60 μm) and diameters (0.2-0.8 μm), and an average of 50% reduction in diameter between their widest and thinnest parts. Ultrastructural analysis revealed submembranous localization of Ank-G at nodes of Ranvier and AIS. Serial ultrathin section analysis and 3D reconstructions revealed that Ank-G colocalized with TH only at the AIS. Few cases of synaptic innervation of the AIS of dopaminergic neurons were observed. mRNA in situ hybridization of brain-specific Nav subunits revealed the expression of Nav 1.2 by most SNc neurons and a small proportion expressing Nav 1.6. The presence of sodium channels, along with the submembranous location of Ank-G is consistent with the role of AIS in action potential generation. Differences in the size of the AIS likely underlie differences in firing pattern, while the tapering diameter of AIS may define a trigger zone for action potentials. Finally, the conspicuous expression of Nav 1.2 by the majority of dopaminergic neurons may explain their high threshold for firing and their low discharge rate.
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Affiliation(s)
- Cristian González-Cabrera
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rodrigo Meza
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.,Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Lorena Ulloa
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Paulina Merino-Sepúlveda
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Valentina Luco
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Ana Sanhueza
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alejandro Oñate-Ponce
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - J Paul Bolam
- MRC Brain Network Dynamics Unit, Department of Pharmacology, University of Oxford, Oxford, United Kingdom
| | - Pablo Henny
- Laboratorio de Neuroanatomía, Departamento de Anatomía, and Centro Interdisciplinario de Neurociencia, NeuroUC, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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Iyer R, Ungless MA, Faisal AA. Calcium-activated SK channels control firing regularity by modulating sodium channel availability in midbrain dopamine neurons. Sci Rep 2017; 7:5248. [PMID: 28701749 PMCID: PMC5507868 DOI: 10.1038/s41598-017-05578-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 05/31/2017] [Indexed: 12/21/2022] Open
Abstract
Dopamine neurons in the substantia nigra pars compacta and ventral tegmental area regulate behaviours such as reward-related learning, and motor control. Dysfunction of these neurons is implicated in Schizophrenia, addiction to drugs, and Parkinson’s disease. While some dopamine neurons fire single spikes at regular intervals, others fire irregular single spikes interspersed with bursts. Pharmacological inhibition of calcium-activated potassium (SK) channels increases the variability in their firing pattern, sometimes also increasing the number of spikes fired in bursts, indicating that SK channels play an important role in maintaining dopamine neuron firing regularity and burst firing. However, the exact mechanisms underlying these effects are still unclear. Here, we develop a biophysical model of a dopamine neuron incorporating ion channel stochasticity that enabled the analysis of availability of ion channels in multiple states during spiking. We find that decreased firing regularity is primarily due to a significant decrease in the AHP that in turn resulted in a reduction in the fraction of available voltage-gated sodium channels due to insufficient recovery from inactivation. Our model further predicts that inhibition of SK channels results in a depolarisation of action potential threshold along with an increase in its variability.
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Affiliation(s)
- Rajeshwari Iyer
- MRC London Institute of Medical Sciences (LMS), Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Mark A Ungless
- MRC London Institute of Medical Sciences (LMS), Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK. .,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK.
| | - Aldo A Faisal
- MRC London Institute of Medical Sciences (LMS), Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK. .,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, Du Cane Road, London, W12 0NN, UK. .,Department of Bioengineering, Imperial College London, London, United Kingdom. .,Department of Computing, Imperial College London, London, United Kingdom.
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Estep CM, Galtieri DJ, Zampese E, Goldberg JA, Brichta L, Greengard P, Surmeier DJ. Transient Activation of GABAB Receptors Suppresses SK Channel Currents in Substantia Nigra Pars Compacta Dopaminergic Neurons. PLoS One 2016; 11:e0169044. [PMID: 28036359 PMCID: PMC5201262 DOI: 10.1371/journal.pone.0169044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 12/09/2016] [Indexed: 12/15/2022] Open
Abstract
Dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) are richly innervated by GABAergic neurons. The postsynaptic effects of GABA on SNc DA neurons are mediated by a mixture of GABAA and GABAB receptors. Although activation of GABAA receptors inhibits spike generation, the consequences of GABAB receptor activation are less well characterized. To help fill this gap, perforated patch recordings were made from young adult mouse SNc DA neurons. Sustained stimulation of GABAB receptors hyperpolarized SNc DA neurons, as previously described. However, transient stimulation of GABAB receptors by optical uncaging of GABA did not; rather, it reduced the opening of small-conductance, calcium-activated K+ (SK) channels and increased the irregularity of spiking. This modulation was attributable to inhibition of adenylyl cyclase and protein kinase A. Thus, because suppression of SK channel activity increases the probability of burst spiking, transient co-activation of GABAA and GABAB receptors could promote a pause-burst pattern of spiking.
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Affiliation(s)
- Chad M. Estep
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Daniel J. Galtieri
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Enrico Zampese
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
| | - Joshua A. Goldberg
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Lars Brichta
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY, United States of America
| | - Paul Greengard
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY, United States of America
| | - D. James Surmeier
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States of America
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Zhao Z, Ma Y, Chen Z, Liu Q, Li Q, Kong D, Yuan K, Hu L, Wang T, Chen X, Peng Y, Jiang W, Yu Y, Liu X. Effects of Feeder Cells on Dopaminergic Differentiation of Human Embryonic Stem Cells. Front Cell Neurosci 2016; 10:291. [PMID: 28066186 PMCID: PMC5168467 DOI: 10.3389/fncel.2016.00291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 12/05/2016] [Indexed: 01/30/2023] Open
Abstract
Mouse embryonic fibroblasts (MEFs) and human foreskin fibroblasts (HFFs) are used for the culture of human embryonic stem cells (hESCs). MEFs and HFFs differed in their capacity to support the proliferation and pluripotency of hESCs and could affect cardiac differentiation potential of hESCs. The aim of this study was to evaluate the effect of MEFs and HFFs feeders on dopaminergic differentiation of hESCs lines. To minimize the impact of culture condition variation, two hESCs lines were cultured on mixed feeder cells (MFCs, MEFs: HFFs = 1:1) and HFFs feeder, respectively, and then were differentiated into dopaminergic (DA) neurons under the identical protocol. Dopaminergic differentiation was evaluated by immunocytochemistry, quantitative fluorescent real-time PCR, transmission and scanning electron microscopy, and patch clamp. Our results demonstrated that these hESCs-derived neurons were genuine and functional DA neurons. However, compared to hESCs line on MFCs feeder, hESCs line on HFFs feeder had a higher proportion of tyrosine hydroxylase (TH) positive cells and expressed higher levels of FOXA2, PITX3, NURR1, and TH genes. In addition, the values of threshold intensity and threshold membrane potential of DA neurons from hESCs line on HFFs feeder were lower than those of DA neurons from hESCs line on the MFCs feeder. In conclusion, HFFs feeder not only facilitated the differentiation of hESCs cells into dopaminergic neurons, but also induced hESCs-derived DA neurons to express higher electrophysiological excitability. Therefore, feeder cells could affect not only dopaminergic differentiation potential of different hESCs lines, but also electrophysiological properties of hESCs-derived DA neurons.
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Affiliation(s)
- Zhenqiang Zhao
- Department of Neurology, Jinling Hospital, Southern Medical UniversityNanjing, China; Department of Neurology, First Affiliated Hospital, Hainan Medical UniversityHaikou, China
| | - Yanlin Ma
- Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical UniversityGuangzhou, China; Hainan Provincial Key Laboratory for Human Reproductive Medicine and Genetic Research, Hainan Reproductive Medical Center, First Affiliated Hospital, Hainan Medical UniversityHaikou, China
| | - Zhibin Chen
- Department of Neurology, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Qian Liu
- Department of Neurology, Jinling Hospital, Southern Medical University Nanjing, China
| | - Qi Li
- Hainan Provincial Key Laboratory for Human Reproductive Medicine and Genetic Research, Hainan Reproductive Medical Center, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Deyan Kong
- Department of Neurology, Jinling Hospital, Southern Medical UniversityNanjing, China; Department of Neurology, Affiliated Ruikang Hospital, Guangxi Traditional Chinese Medical UniversityNanning, China
| | - Kunxiong Yuan
- Department of Neurology, Jinling Hospital, Southern Medical UniversityNanjing, China; Department of Neurology, Central HospitalShenzhen, China
| | - Lan Hu
- Department of Laboratory Medicines, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Tan Wang
- Department of Neurology, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Xiaowu Chen
- Department of Neurology, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Yanan Peng
- Department of Neurology, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Weimin Jiang
- Hainan Provincial Key Laboratory for Human Reproductive Medicine and Genetic Research, Hainan Reproductive Medical Center, First Affiliated Hospital, Hainan Medical University Haikou, China
| | - Yanhong Yu
- Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University Guangzhou, China
| | - Xinfeng Liu
- Department of Neurology, Jinling Hospital, Southern Medical University Nanjing, China
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Morozova EO, Zakharov D, Gutkin BS, Lapish CC, Kuznetsov A. Dopamine Neurons Change the Type of Excitability in Response to Stimuli. PLoS Comput Biol 2016; 12:e1005233. [PMID: 27930673 PMCID: PMC5145155 DOI: 10.1371/journal.pcbi.1005233] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 11/02/2016] [Indexed: 11/18/2022] Open
Abstract
The dynamics of neuronal excitability determine the neuron's response to stimuli, its synchronization and resonance properties and, ultimately, the computations it performs in the brain. We investigated the dynamical mechanisms underlying the excitability type of dopamine (DA) neurons, using a conductance-based biophysical model, and its regulation by intrinsic and synaptic currents. Calibrating the model to reproduce low frequency tonic firing results in N-methyl-D-aspartate (NMDA) excitation balanced by γ-Aminobutyric acid (GABA)-mediated inhibition and leads to type I excitable behavior characterized by a continuous decrease in firing frequency in response to hyperpolarizing currents. Furthermore, we analyzed how excitability type of the DA neuron model is influenced by changes in the intrinsic current composition. A subthreshold sodium current is necessary for a continuous frequency decrease during application of a negative current, and the low-frequency "balanced" state during simultaneous activation of NMDA and GABA receptors. Blocking this current switches the neuron to type II characterized by the abrupt onset of repetitive firing. Enhancing the anomalous rectifier Ih current also switches the excitability to type II. Key characteristics of synaptic conductances that may be observed in vivo also change the type of excitability: a depolarized γ-Aminobutyric acid receptor (GABAR) reversal potential or co-activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) leads to an abrupt frequency drop to zero, which is typical for type II excitability. Coactivation of N-methyl-D-aspartate receptors (NMDARs) together with AMPARs and GABARs shifts the type I/II boundary toward more hyperpolarized GABAR reversal potentials. To better understand how altering each of the aforementioned currents leads to changes in excitability profile of DA neuron, we provide a thorough dynamical analysis. Collectively, these results imply that type I excitability in dopamine neurons might be important for low firing rates and fine-tuning basal dopamine levels, while switching excitability to type II during NMDAR and AMPAR activation may facilitate a transient increase in dopamine concentration, as type II neurons are more amenable to synchronization by mutual excitation.
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Affiliation(s)
- Ekaterina O. Morozova
- Department of Physics, Indiana University, Bloomington, Indiana, United States of America
- Department of Mathematical sciences, Indiana University - Purdue University, Indianapolis, Indiana, United States of America
- * E-mail:
| | | | - Boris S. Gutkin
- Group of Neural Theory, INSERM U960 LNC, IEC, Ecole Normale Superieure PSL University, Paris
- Center for Cognition and Decision Making, NRU HSE, Moscow, Russia
| | - Christopher C. Lapish
- Addiction Neuroscience Program, Indiana University - Purdue University, Indianapolis, Indiana, United States of America
| | - Alexey Kuznetsov
- Department of Mathematical sciences, Indiana University - Purdue University, Indianapolis, Indiana, United States of America
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Covariation of axon initial segment location and dendritic tree normalizes the somatic action potential. Proc Natl Acad Sci U S A 2016; 113:14841-14846. [PMID: 27930291 DOI: 10.1073/pnas.1607548113] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In mammalian neurons, the axon initial segment (AIS) electrically connects the somatodendritic compartment with the axon and converts the incoming synaptic voltage changes into a temporally precise action potential (AP) output code. Although axons often emanate directly from the soma, they may also originate more distally from a dendrite, the implications of which are not well-understood. Here, we show that one-third of the thick-tufted layer 5 pyramidal neurons have an axon originating from a dendrite and are characterized by a reduced dendritic complexity and thinner main apical dendrite. Unexpectedly, the rising phase of somatic APs is electrically indistinguishable between neurons with a somatic or a dendritic axon origin. Cable analysis of the neurons indicated that the axonal axial current is inversely proportional to the AIS distance, denoting the path length between the soma and the start of the AIS, and to produce invariant somatic APs, it must scale with the local somatodendritic capacitance. In agreement, AIS distance inversely correlates with the apical dendrite diameter, and model simulations confirmed that the covariation suffices to normalize the somatic AP waveform. Therefore, in pyramidal neurons, the AIS location is finely tuned with the somatodendritic capacitive load, serving as a homeostatic regulation of the somatic AP in the face of diverse neuronal morphologies.
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Morozova EO, Myroshnychenko M, Zakharov D, di Volo M, Gutkin B, Lapish CC, Kuznetsov A. Contribution of synchronized GABAergic neurons to dopaminergic neuron firing and bursting. J Neurophysiol 2016; 116:1900-1923. [PMID: 27440240 PMCID: PMC5144690 DOI: 10.1152/jn.00232.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 07/17/2016] [Indexed: 12/29/2022] Open
Abstract
In the ventral tegmental area (VTA), interactions between dopamine (DA) and γ-aminobutyric acid (GABA) neurons are critical for regulating DA neuron activity and thus DA efflux. To provide a mechanistic explanation of how GABA neurons influence DA neuron firing, we developed a circuit model of the VTA. The model is based on feed-forward inhibition and recreates canonical features of the VTA neurons. Simulations revealed that γ-aminobutyric acid (GABA) receptor (GABAR) stimulation can differentially influence the firing pattern of the DA neuron, depending on the level of synchronization among GABA neurons. Asynchronous activity of GABA neurons provides a constant level of inhibition to the DA neuron and, when removed, produces a classical disinhibition burst. In contrast, when GABA neurons are synchronized by common synaptic input, their influence evokes additional spikes in the DA neuron, resulting in increased measures of firing and bursting. Distinct from previous mechanisms, the increases were not based on lowered firing rate of the GABA neurons or weaker hyperpolarization by the GABAR synaptic current. This phenomenon was induced by GABA-mediated hyperpolarization of the DA neuron that leads to decreases in intracellular calcium (Ca2+) concentration, thus reducing the Ca2+-dependent potassium (K+) current. In this way, the GABA-mediated hyperpolarization replaces Ca2+-dependent K+ current; however, this inhibition is pulsatile, which allows the DA neuron to fire during the rhythmic pauses in inhibition. Our results emphasize the importance of inhibition in the VTA, which has been discussed in many studies, and suggest a novel mechanism whereby computations can occur locally.
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Affiliation(s)
- Ekaterina O Morozova
- Department of Physics, Indiana University, Bloomington, Indiana; Department of Mathematical Sciences, Indiana University-Purdue University, Indianapolis, Indiana;
| | - Maxym Myroshnychenko
- Program in Neuroscience, Indiana University, Bloomington, Indiana; Addiction Neuroscience Program, Indiana University-Purdue University, Indianapolis, Indiana; and
| | - Denis Zakharov
- Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia
| | - Matteo di Volo
- Department of Mathematical Sciences, Indiana University-Purdue University, Indianapolis, Indiana; Group of Neural Theory, INSERM U960, Laboratoire de Neurosciences Cognitives, Institut d'Etude de Cognition, Ecole Normale Superieure, Paris Sciences et Lettres Research University, Paris, France
| | - Boris Gutkin
- Group of Neural Theory, INSERM U960, Laboratoire de Neurosciences Cognitives, Institut d'Etude de Cognition, Ecole Normale Superieure, Paris Sciences et Lettres Research University, Paris, France; Center for Cognition and Decision Making, National Research University Higher School of Economics, Moscow, Russia
| | - Christopher C Lapish
- Addiction Neuroscience Program, Indiana University-Purdue University, Indianapolis, Indiana; and
| | - Alexey Kuznetsov
- Department of Mathematical Sciences, Indiana University-Purdue University, Indianapolis, Indiana
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44
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Canavier CC, Evans RC, Oster AM, Pissadaki EK, Drion G, Kuznetsov AS, Gutkin BS. Implications of cellular models of dopamine neurons for disease. J Neurophysiol 2016; 116:2815-2830. [PMID: 27582295 DOI: 10.1152/jn.00530.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 08/24/2016] [Indexed: 12/21/2022] Open
Abstract
This review addresses the present state of single-cell models of the firing pattern of midbrain dopamine neurons and the insights that can be gained from these models into the underlying mechanisms for diseases such as Parkinson's, addiction, and schizophrenia. We will explain the analytical technique of separation of time scales and show how it can produce insights into mechanisms using simplified single-compartment models. We also use morphologically realistic multicompartmental models to address spatially heterogeneous aspects of neural signaling and neural metabolism. Separation of time scale analyses are applied to pacemaking, bursting, and depolarization block in dopamine neurons. Differences in subpopulations with respect to metabolic load are addressed using multicompartmental models.
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Affiliation(s)
- Carmen C Canavier
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana;
| | - Rebekah C Evans
- Cellular Neurophysiology Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Andrew M Oster
- Department of Mathematics, Eastern Washington University, Cheney, Washington
| | - Eleftheria K Pissadaki
- IBM T.J. Watson Research Center, Yorktown Heights, New York.,Department of Computer Science, University of Sheffield, Sheffield, United Kingdom
| | - Guillaume Drion
- Department of Electrical Engineering and Computer Science, University of Liege, Liege, Belgium
| | - Alexey S Kuznetsov
- Department of Mathematical Sciences and Center for Mathematical Biosciences, Indiana University, Purdue University Indianapolis, Indianapolis, Indiana
| | - Boris S Gutkin
- Group for Neural Theory, LNC INSERM U960, Département d'Études Cognitives, École Normale Supérieure PSL Research University, Paris, France.,Center for Cognition and Decision Making, NRU Higher School of Economics, Moscow, Russia; and
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45
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Pearlstein E, Michel FJ, Save L, Ferrari DC, Hammond C. Abnormal Development of Glutamatergic Synapses Afferent to Dopaminergic Neurons of the Pink1(-/-) Mouse Model of Parkinson's Disease. Front Cell Neurosci 2016; 10:168. [PMID: 27445695 PMCID: PMC4917553 DOI: 10.3389/fncel.2016.00168] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 06/09/2016] [Indexed: 11/13/2022] Open
Abstract
In a preceding study, we showed that in adult pink1−/− mice, a monogenic animal model of Parkinson’s disease (PD), striatal neurons display aberrant electrical activities that precede the onset of overt clinical manifestations. Here, we tested the hypothesis that the maturation of dopaminergic (DA) neurons of the pink1−/− substantia nigra compacta (SNc) follows, from early stages on, a different developmental trajectory from age-matched wild type (wt) SNc DA neurons. We used immature (postnatal days P2–P10) and young adult (P30–P90) midbrain slices of pink1−/− mice expressing the green fluorescent protein in tyrosine hydroxylase (TH)-positive neurons. We report that the developmental sequence of N-Methyl-D-aspartic acid (NMDA) spontaneous excitatory postsynaptic currents (sEPSCs) is altered in pink1−/− SNc DA neurons, starting from shortly after birth. They lack the transient episode of high NMDA receptor-mediated neuronal activity characteristic of the immature stage of wt SNc DA neurons. The maturation of the membrane resistance of pink1−/− SNc DA neurons is also altered. Collectively, these observations suggest that electrical manifestations occurring shortly after birth in SNc DA neurons might lead to dysfunction in dopamine release and constitute an early pathogenic mechanism of PD.
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Affiliation(s)
- Edouard Pearlstein
- UMR901, Aix-Marseille UniversitéMarseille, France; Institut de Neurobiologie de la Méditerranée (INMED), Inserm UMR 901Marseille, France
| | - François J Michel
- UMR901, Aix-Marseille UniversitéMarseille, France; Institut de Neurobiologie de la Méditerranée (INMED), Inserm UMR 901Marseille, France
| | - Laurène Save
- UMR901, Aix-Marseille UniversitéMarseille, France; Institut de Neurobiologie de la Méditerranée (INMED), Inserm UMR 901Marseille, France
| | - Diana C Ferrari
- UMR901, Aix-Marseille UniversitéMarseille, France; Institut de Neurobiologie de la Méditerranée (INMED), Inserm UMR 901Marseille, France
| | - Constance Hammond
- UMR901, Aix-Marseille UniversitéMarseille, France; Institut de Neurobiologie de la Méditerranée (INMED), Inserm UMR 901Marseille, France
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Zakharov D, Lapish C, Gutkin B, Kuznetsov A. Synergy of AMPA and NMDA Receptor Currents in Dopaminergic Neurons: A Modeling Study. Front Comput Neurosci 2016; 10:48. [PMID: 27252643 PMCID: PMC4877376 DOI: 10.3389/fncom.2016.00048] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 05/06/2016] [Indexed: 11/13/2022] Open
Abstract
Dopaminergic (DA) neurons display two modes of firing: low-frequency tonic and high-frequency bursts. The high frequency firing within the bursts is attributed to NMDA, but not AMPA receptor activation. In our models of the DA neuron, both biophysical and abstract, the NMDA receptor current can significantly increase their firing frequency, whereas the AMPA receptor current is not able to evoke high-frequency activity and usually suppresses firing. However, both currents are produced by glutamate receptors and, consequently, are often co-activated. Here we consider combined influence of AMPA and NMDA synaptic input in the models of the DA neuron. Different types of neuronal activity (resting state, low frequency, or high frequency firing) are observed depending on the conductance of the AMPAR and NMDAR currents. In two models, biophysical and reduced, we show that the firing frequency increases more effectively if both receptors are co-activated for certain parameter values. In particular, in the more quantitative biophysical model, the maximal frequency is 40% greater than that with NMDAR alone. The dynamical mechanism of such frequency growth is explained in the framework of phase space evolution using the reduced model. In short, both the AMPAR and NMDAR currents flatten the voltage nullcline, providing the frequency increase, whereas only NMDA prevents complete unfolding of the nullcline, providing robust firing. Thus, we confirm a major role of the NMDAR in generating high-frequency firing and conclude that AMPAR activation further significantly increases the frequency.
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Affiliation(s)
- Denis Zakharov
- Nonlinear Dynamics Department, Institute of Applied Physics, Russian Academy of Science (RAS) Nizhny Novgorod, Russia
| | - Christopher Lapish
- Department of Psychology, Indiana University-Purdue University Indianapolis (IUPUI) Indianapolis, IN, USA
| | - Boris Gutkin
- Group of Neural Theory, Ecole Normale Supérieure (ENS)Paris, France; Centre for Cognition and Decision Making, National Research University Higher School of EconomicsMoscow, Russia
| | - Alexey Kuznetsov
- Department of Mathematical Sciences and Center for Mathematical Modeling and Computational Sciences, Indiana University-Purdue University Indianapolis (IUPUI) Indianapolis, IN, USA
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Differential Regulation of Action Potential Shape and Burst-Frequency Firing by BK and Kv2 Channels in Substantia Nigra Dopaminergic Neurons. J Neurosci 2016; 35:16404-17. [PMID: 26674866 DOI: 10.1523/jneurosci.5291-14.2015] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
UNLABELLED Little is known about the voltage-dependent potassium currents underlying spike repolarization in midbrain dopaminergic neurons. Studying mouse substantia nigra pars compacta dopaminergic neurons both in brain slice and after acute dissociation, we found that BK calcium-activated potassium channels and Kv2 channels both make major contributions to the depolarization-activated potassium current. Inhibiting Kv2 or BK channels had very different effects on spike shape and evoked firing. Inhibiting Kv2 channels increased spike width and decreased the afterhyperpolarization, as expected for loss of an action potential-activated potassium conductance. BK inhibition also increased spike width but paradoxically increased the afterhyperpolarization. Kv2 channel inhibition steeply increased the slope of the frequency-current (f-I) relationship, whereas BK channel inhibition had little effect on the f-I slope or decreased it, sometimes resulting in slowed firing. Action potential clamp experiments showed that both BK and Kv2 current flow during spike repolarization but with very different kinetics, with Kv2 current activating later and deactivating more slowly. Further experiments revealed that inhibiting either BK or Kv2 alone leads to recruitment of additional current through the other channel type during the action potential as a consequence of changes in spike shape. Enhancement of slowly deactivating Kv2 current can account for the increased afterhyperpolarization produced by BK inhibition and likely underlies the very different effects on the f-I relationship. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell. SIGNIFICANCE STATEMENT This work shows that BK calcium-activated potassium channels and Kv2 voltage-activated potassium channels both regulate action potentials in dopamine neurons of the substantia nigra pars compacta. Although both channel types participate in action potential repolarization about equally, they have contrasting and partially opposite effects in regulating neuronal firing at frequencies typical of bursting. Our analysis shows that this results from their different kinetic properties, with fast-activating BK channels serving to short-circuit activation of Kv2 channels, which tend to slow firing by producing a deep afterhyperpolarization. The cross-regulation of BK and Kv2 activation illustrates that the functional role of a channel cannot be defined in isolation but depends critically on the context of the other conductances in the cell.
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48
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Zakharov D, Kuznetsov A. Qualitatively different scenarios for co-activation of NMDA, AMPA and GABA receptor currents on dopaminergic neuron. BMC Neurosci 2015. [PMCID: PMC4697515 DOI: 10.1186/1471-2202-16-s1-p138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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49
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Coexistence of glutamatergic spine synapses and shaft synapses in substantia nigra dopamine neurons. Sci Rep 2015; 5:14773. [PMID: 26435058 PMCID: PMC4593176 DOI: 10.1038/srep14773] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 09/09/2015] [Indexed: 02/01/2023] Open
Abstract
Dopamine neurons of the substantia nigra have long been believed to have multiple aspiny dendrites which receive many glutamatergic synaptic inputs from several regions of the brain. But, here, using high-resolution two-photon confocal microscopy in the mouse brain slices, we found a substantial number of common dendritic spines in the nigral dopamine neurons including thin, mushroom, and stubby types of spines. However, the number of dendritic spines of the dopamine neurons was approximately five times lower than that of CA1 pyramidal neurons. Immunostaining and morphological analysis revealed that glutamatergic shaft synapses were present two times more than spine synapses. Using local two-photon glutamate uncaging techniques, we confirmed that shaft synapses and spine synapses had both AMPA and NMDA receptors, but the AMPA/NMDA current ratios differed. The evoked postsynaptic potentials of spine synapses showed lower amplitudes but longer half-widths than those of shaft synapses. Therefore, we provide the first evidence that the midbrain dopamine neurons have two morphologically and functionally distinct types of glutamatergic synapses, spine synapses and shaft synapses, on the same dendrite. This peculiar organization could be a new basis for unraveling many physiological and pathological functions of the midbrain dopamine neurons.
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50
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Oster A, Faure P, Gutkin BS. Mechanisms for multiple activity modes of VTA dopamine neurons. Front Comput Neurosci 2015; 9:95. [PMID: 26283955 PMCID: PMC4516885 DOI: 10.3389/fncom.2015.00095] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/05/2015] [Indexed: 11/20/2022] Open
Abstract
Midbrain ventral segmental area (VTA) dopaminergic neurons send numerous projections to cortical and sub-cortical areas, and diffusely release dopamine (DA) to their targets. DA neurons display a range of activity modes that vary in frequency and degree of burst firing. Importantly, DA neuronal bursting is associated with a significantly greater degree of DA release than an equivalent tonic activity pattern. Here, we introduce a single compartmental, conductance-based computational model for DA cell activity that captures the behavior of DA neuronal dynamics and examine the multiple factors that underlie DA firing modes: the strength of the SK conductance, the amount of drive, and GABA inhibition. Our results suggest that neurons with low SK conductance fire in a fast firing mode, are correlated with burst firing, and require higher levels of applied current before undergoing depolarization block. We go on to consider the role of GABAergic inhibition on an ensemble of dynamical classes of DA neurons and find that strong GABA inhibition suppresses burst firing. Our studies suggest differences in the distribution of the SK conductance and GABA inhibition levels may indicate subclasses of DA neurons within the VTA. We further identify, that by considering alternate potassium dynamics, the dynamics display burst patterns that terminate via depolarization block, akin to those observed in vivo in VTA DA neurons and in substantia nigra pars compacta (SNc) DA cell preparations under apamin application. In addition, we consider the generation of transient burst firing events that are NMDA-initiated or elicited by a sudden decrease of GABA inhibition, that is, disinhibition.
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Affiliation(s)
- Andrew Oster
- Department of Mathematics, Eastern Washington University Cheney, WA, USA ; Group for Neural Theory, LNC INSERM Unité 960, Département d'Études Cognitives, École Normale Supérieure Paris, France
| | - Philippe Faure
- Sorbonne Université, Neuroscience Paris Seine, CNRS UMR 8246, INSERM U 1130, Université Pierre et Marie Curie Univ Paris, UM119 Paris, France
| | - Boris S Gutkin
- Group for Neural Theory, LNC INSERM Unité 960, Département d'Études Cognitives, École Normale Supérieure Paris, France ; Center for Cognition and Decision Making, National Research University Higher School of Economics Moscow, Russia
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