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Song J, Lin H, Liu S. Basal ganglia network dynamics and function: Role of direct, indirect and hyper-direct pathways in action selection. NETWORK (BRISTOL, ENGLAND) 2023; 34:84-121. [PMID: 36856435 DOI: 10.1080/0954898x.2023.2173816] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/11/2022] [Accepted: 01/23/2023] [Indexed: 06/18/2023]
Abstract
Basal ganglia (BG) are a widely recognized neural basis for action selection, but its decision-making mechanism is still a difficult problem for researchers. Therefore, we constructed a spiking neural network inspired by the BG anatomical data. Simulation experiments were based on the principle of dis-inhibition and our functional hypothesis within the BG: the direct pathway, the indirect pathway, and the hyper-direct pathway of the BG jointly implement the initiation execution and termination of motor programs. Firstly, we studied the dynamic process of action selection with the network, which contained intra-group competition and inter-group competition. Secondly, we focused on the effects of the stimulus intensity and the proportion of excitation and inhibition on the GPi/SNr. The results suggested that inhibition and excitation shape action selection. They also explained why the firing rate of GPi/SNr did not continue to increase in the action-selection experiment. Finally, we discussed the experimental results with the functional hypothesis. Uniquely, this paper summarized the decision-making neural mechanism of action selection based on the direct pathway, the indirect pathway, and the hyper-direct pathway within BG.
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Affiliation(s)
- Jian Song
- School of Mathematics, South China University of Technology, Guangzhou, China
| | - Hui Lin
- Department of Precision Instruments, Tsinghua University, Beijing, China
| | - Shenquan Liu
- School of Mathematics, South China University of Technology, Guangzhou, China
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2
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Song JL, Westover MB, Zhang R. A mechanistic model of calcium homeostasis leading to occurrence and propagation of secondary brain injury. J Neurophysiol 2022; 128:1168-1180. [PMID: 36197012 PMCID: PMC9621713 DOI: 10.1152/jn.00045.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 09/13/2022] [Accepted: 09/27/2022] [Indexed: 11/22/2022] Open
Abstract
Secondary brain injury (SBI) refers to new or worsening brain insult after primary brain injury (PBI). Neurophysiological experiments show that calcium (Ca2+) is one of the major culprits that contribute to neuronal damage and death following PBI. However, mechanistic details about how alterations of Ca2+ levels contribute to SBI are not well characterized. In this paper, we first build a biophysical model for SBI related to calcium homeostasis (SBI-CH) to study the mechanistic details of PBI-induced disruption of CH, and how these disruptions affect the occurrence of SBI. Then, we construct a coupled SBI-CH model by formulating synaptic interactions to investigate how disruption of CH affects synaptic function and further promotes the propagation of SBI between neurons. Our model shows how the opening of voltage-gated calcium channels (VGCCs), decreasing of plasma membrane calcium pump (PMCA), and reversal of the Na+/Ca2+ exchanger (NCX) during and following PBI, could induce disruption of CH and further promote SBI. We also show that disruption of CH causes synaptic dysfunction, which further induces loss of excitatory-inhibitory balance in the system, and this might promote the propagation of SBI and cause neighboring tissue to be injured. Our findings offer a more comprehensive understanding of the complex interrelationship between CH and SBI.NEW & NOTEWORTHY We build a mechanistic model SBI-CH for calcium homeostasis (CH) to study how alterations of Ca2+ levels following PBI affect the occurrence and propagation of SBI. Specifically, we investigate how the opening of VGCCs, decreasing of PMCA, and reversal of NCX disrupt CH, and further induce the occurrence of SBI. We also present a coupled SBI-CH model to show how disrupted CH causes synaptic dysfunction, and further promotes the propagation of SBI between neurons.
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Affiliation(s)
- Jiang-Ling Song
- The Medical Big Data Research Center, Northwest University, Xi'an, People's Republic of China
| | - M Brandon Westover
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts
| | - Rui Zhang
- The Medical Big Data Research Center, Northwest University, Xi'an, People's Republic of China
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3
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Ben-Shalom R, Ladd A, Artherya NS, Cross C, Kim KG, Sanghevi H, Korngreen A, Bouchard KE, Bender KJ. NeuroGPU: Accelerating multi-compartment, biophysically detailed neuron simulations on GPUs. J Neurosci Methods 2022; 366:109400. [PMID: 34728257 PMCID: PMC9887806 DOI: 10.1016/j.jneumeth.2021.109400] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Revised: 10/09/2021] [Accepted: 10/27/2021] [Indexed: 02/03/2023]
Abstract
BACKGROUND The membrane potential of individual neurons depends on a large number of interacting biophysical processes operating on spatial-temporal scales spanning several orders of magnitude. The multi-scale nature of these processes dictates that accurate prediction of membrane potentials in specific neurons requires the utilization of detailed simulations. Unfortunately, constraining parameters within biologically detailed neuron models can be difficult, leading to poor model fits. This obstacle can be overcome partially by numerical optimization or detailed exploration of parameter space. However, these processes, which currently rely on central processing unit (CPU) computation, often incur orders of magnitude increases in computing time for marginal improvements in model behavior. As a result, model quality is often compromised to accommodate compute resources. NEW METHOD Here, we present a simulation environment, NeuroGPU, that takes advantage of the inherent parallelized structure of the graphics processing unit (GPU) to accelerate neuronal simulation. RESULTS & COMPARISON WITH EXISTING METHODS NeuroGPU can simulate most biologically detailed models 10-200 times faster than NEURON simulation running on a single core and 5 times faster than GPU simulators (CoreNEURON). NeuroGPU is designed for model parameter tuning and best performs when the GPU is fully utilized by running multiple (> 100) instances of the same model with different parameters. When using multiple GPUs, NeuroGPU can reach to a speed-up of 800 fold compared to single core simulations, especially when simulating the same model morphology with different parameters. We demonstrate the power of NeuoGPU through large-scale parameter exploration to reveal the response landscape of a neuron. Finally, we accelerate numerical optimization of biophysically detailed neuron models to achieve highly accurate fitting of models to simulation and experimental data. CONCLUSIONS Thus, NeuroGPU is the fastest available platform that enables rapid simulation of multi-compartment, biophysically detailed neuron models on commonly used computing systems accessible by many scientists.
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Affiliation(s)
- Roy Ben-Shalom
- Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States; Department of Neurology, University of California, San Francisco, San Francisco, CA, United States; MIND Institute University of California, Davis, CA, United States; Computational Research Division, Lawrence Berkeley National Lab, Berkeley, CA, United States.
| | - Alexander Ladd
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, United States
| | - Nikhil S Artherya
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, United States
| | - Christopher Cross
- Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States
| | - Kyung Geun Kim
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, United States
| | - Hersh Sanghevi
- Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA, United States
| | - Alon Korngreen
- The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel; The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Kristofer E Bouchard
- Computational Research Division, Lawrence Berkeley National Lab, Berkeley, CA, United States; Hellen Wills Neuroscience Institute & Redwood Center for Theoretical Neuroscience, University of California, Berkeley, Berkeley, CA, United States; Biological Systems and Engineering Division, Lawrence Berkeley National Lab, Berkeley, CA, United States
| | - Kevin J Bender
- Weill Institute for Neurosciences, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA, United States; Department of Neurology, University of California, San Francisco, San Francisco, CA, United States.
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4
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Conventional measures of intrinsic excitability are poor estimators of neuronal activity under realistic synaptic inputs. PLoS Comput Biol 2021; 17:e1009378. [PMID: 34529674 PMCID: PMC8478185 DOI: 10.1371/journal.pcbi.1009378] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 09/28/2021] [Accepted: 08/24/2021] [Indexed: 11/19/2022] Open
Abstract
Activity-dependent regulation of intrinsic excitability has been shown to greatly contribute to the overall plasticity of neuronal circuits. Such neuroadaptations are commonly investigated in patch clamp experiments using current step stimulation and the resulting input-output functions are analyzed to quantify alterations in intrinsic excitability. However, it is rarely addressed, how such changes translate to the function of neurons when they operate under natural synaptic inputs. Still, it is reasonable to expect that a strong correlation and near proportional relationship exist between static firing responses and those evoked by synaptic drive. We challenge this view by performing a high-yield electrophysiological analysis of cultured mouse hippocampal neurons using both standard protocols and simulated synaptic inputs via dynamic clamp. We find that under these conditions the neurons exhibit vastly different firing responses with surprisingly weak correlation between static and dynamic firing intensities. These contrasting responses are regulated by two intrinsic K-currents mediated by Kv1 and Kir channels, respectively. Pharmacological manipulation of the K-currents produces differential regulation of the firing output of neurons. Static firing responses are greatly increased in stuttering type neurons under blocking their Kv1 channels, while the synaptic responses of the same neurons are less affected. Pharmacological blocking of Kir-channels in delayed firing type neurons, on the other hand, exhibit the opposite effects. Our subsequent computational model simulations confirm the findings in the electrophysiological experiments and also show that adaptive changes in the kinetic properties of such currents can even produce paradoxical regulation of the firing output.
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Tossell K, Dodhia RA, Galet B, Tkachuk O, Ungless MA. Tonic GABAergic inhibition, via GABA A receptors containing αβƐ subunits, regulates excitability of ventral tegmental area dopamine neurons. Eur J Neurosci 2021; 53:1722-1737. [PMID: 33522050 PMCID: PMC8651010 DOI: 10.1111/ejn.15133] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 12/15/2020] [Accepted: 01/18/2021] [Indexed: 12/13/2022]
Abstract
The activity of midbrain dopamine neurons is strongly regulated by fast synaptic inhibitory γ‐Aminobutyric acid (GABA)ergic inputs. There is growing evidence in other brain regions that low concentrations of ambient GABA can persistently activate certain subtypes of GABAA receptor to generate a tonic current. However, evidence for a tonic GABAergic current in midbrain dopamine neurons is limited. To address this, we conducted whole‐cell recordings from ventral tegmental area (VTA) dopamine neurons in brain slices from mice. We found that application of GABAA receptor antagonists decreased the holding current, indicating the presence of a tonic GABAergic input. Global increases in GABA release, induced by either a nitric oxide donor or inhibition of GABA uptake, further increased this tonic current. Importantly, prolonged inhibition of the firing activity of local GABAergic neurons abolished the tonic current. A combination of pharmacology and immunohistochemistry experiments suggested that, unlike common examples of tonic inhibition, this current may be mediated by a relatively unusual combination of α4βƐ subunits. Lastly, we found that the tonic current reduced excitability in dopamine neurons suggesting a subtractive effect on firing activity.
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Affiliation(s)
- Kyoko Tossell
- MRC London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
| | - Rakesh A Dodhia
- MRC London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
| | - Benjamin Galet
- MRC London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
| | - Olga Tkachuk
- MRC London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
| | - Mark A Ungless
- MRC London Institute of Medical Sciences (LMS), London, UK.,Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, UK
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6
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Homeostatic plasticity and burst activity are mediated by hyperpolarization-activated cation currents and T-type calcium channels in neuronal cultures. Sci Rep 2021; 11:3236. [PMID: 33547341 PMCID: PMC7864958 DOI: 10.1038/s41598-021-82775-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 01/20/2021] [Indexed: 01/27/2023] Open
Abstract
Homeostatic plasticity stabilizes neuronal networks by adjusting the responsiveness of neurons according to their global activity and the intensity of the synaptic inputs. We investigated the homeostatic regulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) and T-type calcium (CaV3) channels in dissociated and organotypic slice cultures. After 48 h blocking of neuronal activity by tetrodotoxin (TTX), our patch-clamp experiments revealed an increase in the depolarizing voltage sag and post-inhibitory rebound mediated by HCN and CaV3 channels, respectively. All HCN subunits (HCN1 to 4) and T-type Ca-channel subunits (CaV3.1, 3.2 and 3.3) were expressed in both control and activity-deprived hippocampal cultures. Elevated expression levels of CaV3.1 mRNA and a selective increase in the expression of TRIP8b exon 4 isoforms, known to regulate HCN channel localization, were also detected in TTX-treated cultured hippocampal neurons. Immunohistochemical staining in TTX-treated organotypic slices verified a more proximal translocation of HCN1 channels in CA1 pyramidal neurons. Computational modeling also implied that HCN and T-type calcium channels have important role in the regulation of synchronized bursting evoked by previous activity-deprivation. Thus, our findings indicate that HCN and T-type Ca-channels contribute to the homeostatic regulation of excitability and integrative properties of hippocampal neurons.
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7
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Masrouri H, Azadi M, Semnanian S, Azizi H. Maternal deprivation induces persistent adaptations in putative dopamine neurons in rat ventral tegmental area: in vivo electrophysiological study. Exp Brain Res 2020; 238:2221-2228. [PMID: 32705295 DOI: 10.1007/s00221-020-05884-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/13/2020] [Indexed: 12/23/2022]
Abstract
Early life aversive experiences can trigger persistent deficits in neuronal signaling within the mesolimbic pathway, most notably in the dopamine (DA) neurons of the ventral tegmental area (VTA). The identity of such cellular mechanisms currently appears as an important issue. To address this concern, we investigated whether early life maternal deprivation (MD) would affect the electrical activity of VTA DA neurons, via in vivo extracellular single-unit recording. Male Wistar rats were deprived of their dams for 3 h per day from postnatal days (PND) 1-14. Thereafter, the adult animals (PND 70-80) were tested for the discharge activity of putative VTA DA neurons. The VTA DA neurons displayed a decrease in firing rate and an increase in the variability of baseline discharge activity in deprived animals. MD also caused a decrease in burst firing of VTA DA neurons compared to control subjects. In summary, early life MD induces a hypoactive VTA DA system, which may contribute to lifespan psychopathologies.
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Affiliation(s)
- Hossein Masrouri
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Maryam Azadi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Saeed Semnanian
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
| | - Hossein Azizi
- Department of Physiology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
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8
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Aberg KC, Kramer EE, Schwartz S. Interplay between midbrain and dorsal anterior cingulate regions arbitrates lingering reward effects on memory encoding. Nat Commun 2020; 11:1829. [PMID: 32286275 PMCID: PMC7156375 DOI: 10.1038/s41467-020-15542-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 03/12/2020] [Indexed: 12/17/2022] Open
Abstract
Rewarding events enhance memory encoding via dopaminergic influences on hippocampal plasticity. Phasic dopamine release depends on immediate reward magnitude, but presumably also on tonic dopamine levels, which may vary as a function of the average accumulation of reward over time. Using model-based fMRI in combination with a novel associative memory task, we show that immediate reward magnitude exerts a monotonically increasing influence on the nucleus accumbens, ventral tegmental area (VTA), and hippocampal activity during encoding, and enhances memory. By contrast, average reward levels modulate feedback-related responses in the VTA and hippocampus in a non-linear (inverted U-shape) fashion, with similar effects on memory performance. Additionally, the dorsal anterior cingulate cortex (dACC) monotonically tracks average reward levels, while VTA-dACC functional connectivity is non-linearly modulated (inverted U-shape) by average reward. We propose that the dACC computes the net behavioral impact of average reward and relays this information to memory circuitry via the VTA.
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Affiliation(s)
| | - Emily Elizabeth Kramer
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada
| | - Sophie Schwartz
- Department of Neuroscience, University of Geneva, Geneva, Switzerland.,Swiss Center for Affective Sciences, University of Geneva, Geneva, Switzerland.,Geneva Neuroscience Center, University of Geneva, Geneva, Switzerland
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9
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Brodnik ZD, Black EM, España RA. Accelerated development of cocaine-associated dopamine transients and cocaine use vulnerability following traumatic stress. Neuropsychopharmacology 2020; 45:472-481. [PMID: 31539899 PMCID: PMC6969179 DOI: 10.1038/s41386-019-0526-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 09/06/2019] [Accepted: 09/11/2019] [Indexed: 12/21/2022]
Abstract
Post-traumatic stress disorder and cocaine use disorder are highly co-morbid psychiatric conditions. The onset of post-traumatic stress disorder generally occurs prior to the development of cocaine use disorder, and thus it appears that the development of post-traumatic stress disorder drives cocaine use vulnerability. We recently characterized a rat model of post-traumatic stress disorder with segregation of rats as susceptible and resilient based on anxiety-like behavior in the elevated plus maze and context avoidance. We paired this model with in vivo fast scan cyclic voltammetry in freely moving rats to test for differences in dopamine signaling in the nucleus accumbens core at baseline, in response to a single dose of cocaine, and in response to cocaine-paired cues. Further, we examined differences in the acquisition of cocaine self-administration across groups. Results indicate that susceptibility to traumatic stress is associated with alterations in phasic dopamine signaling architecture that increase the rate at which dopamine signals entrain to cocaine-associated cues and increase the magnitude of persistent cue-evoked dopamine signals following training. These changes in phasic dopamine signaling correspond with increases in the rate at which susceptible rats develop excessive cocaine-taking behavior. Together, our studies demonstrate that susceptibility to traumatic stress is associated with a cocaine use-vulnerable phenotype and suggests that differences in phasic dopamine signaling architecture may contribute to the process by which this vulnerability occurs.
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Affiliation(s)
- Zachary D. Brodnik
- 0000 0001 2181 3113grid.166341.7Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900W Queen Lane, Philadelphia, PA 19129 USA
| | - Emily M. Black
- 0000 0001 2181 3113grid.166341.7Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900W Queen Lane, Philadelphia, PA 19129 USA
| | - Rodrigo A. España
- 0000 0001 2181 3113grid.166341.7Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900W Queen Lane, Philadelphia, PA 19129 USA
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10
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Liu S, Borgland SL. Insulin actions in the mesolimbic dopamine system. Exp Neurol 2019; 320:113006. [DOI: 10.1016/j.expneurol.2019.113006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 05/21/2019] [Accepted: 07/03/2019] [Indexed: 01/22/2023]
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11
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Alternative classifications of neurons based on physiological properties and synaptic responses, a computational study. Sci Rep 2019; 9:13096. [PMID: 31511545 PMCID: PMC6739481 DOI: 10.1038/s41598-019-49197-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 08/16/2019] [Indexed: 01/25/2023] Open
Abstract
One of the central goals of today's neuroscience is to achieve the conceivably most accurate classification of neuron types in the mammalian brain. As part of this research effort, electrophysiologists commonly utilize current clamp techniques to gain a detailed characterization of the neurons' physiological properties. While this approach has been useful, it is not well understood whether neurons that share physiological properties of a particular phenotype would also operate consistently under the action of natural synaptic inputs. We approached this problem by simulating a biophysically diverse population of model neurons based on 3 generic phenotypes. We exposed the model neurons to two types of stimulation to investigate their voltage responses under conventional current step protocols and under simulated synaptic bombardment. We extracted standard physiological parameters from the voltage responses elicited by current step stimulation and spike arrival times descriptive of the model's firing behavior under synaptic inputs. The biophysical phenotypes could be reliably identified using classification based on the 'static' physiological properties, but not the interspike interval-based parameters. However, the model neurons associated with the biophysically different phenotypes retained cell type specific features in the fine structure of their spike responses that allowed their accurate classification.
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12
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Xiao L, Priest MF, Kozorovitskiy Y. Oxytocin functions as a spatiotemporal filter for excitatory synaptic inputs to VTA dopamine neurons. eLife 2018; 7:33892. [PMID: 29676731 PMCID: PMC5910020 DOI: 10.7554/elife.33892] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 03/26/2018] [Indexed: 01/15/2023] Open
Abstract
The experience of rewarding or aversive stimuli is encoded by distinct afferents to dopamine (DA) neurons of the ventral tegmental area (VTA). Several neuromodulatory systems including oxytocin regulate DA neuron excitability and synaptic transmission that process socially meaningful stimuli. We and others have recently characterized oxytocinergic modulation of activity in mouse VTA DA neurons, but the mechanisms underlying oxytocinergic modulation of synaptic transmission in DA neurons remain poorly understood. Here, we find that oxytocin application or optogenetic release decrease excitatory synaptic transmission, via long lasting, presynaptic, endocannabinoid-dependent mechanisms. Oxytocin modulation of excitatory transmission alters the magnitude of short and long-term depression. We find that only some glutamatergic projections to DA neurons express CB1 receptors. Optogenetic stimulation of three major VTA inputs demonstrates that oxytocin modulation is limited to projections that show evidence of CB1R transcripts. Thus, oxytocin gates information flow into reward circuits in a temporally selective and pathway-specific manner. The mammalian brain contains millions of nerve cells or neurons that communicate with each other via a process called neurotransmission. To send a message to its neighbor, a neuron releases a chemical called a neurotransmitter into the space between the cells. The neurotransmitter then binds to receiver proteins on the target cell. Another group of chemicals, known as neuromodulators, regulate this process, adjusting the way that neurons respond to neurotransmitters. In doing so, they help regulate many types of behavior in mammals. The neuromodulator oxytocin, for example, has earned the nickname ‘the love hormone’ because it promotes social behavior and bonding. It does this in part by altering the activity of neurons in a brain region called the ventral tegmental area (VTA). These neurons produce the brain’s main reward signal, dopamine, which is itself a neuromodulator. But exactly how oxytocin affects the activity of dopamine-producing neurons is unclear. By recording from individual neurons in slices of mouse brain tissue, Xiao et al. show that oxytocin filters inputs to dopamine neurons in the VTA. It does this by making the dopamine neurons release another group of reward signals, known as endocannabinoids. These are the brain’s own version of the chemicals found inside cannabis plants. The endocannabinoids bind to neurons that provide input to the VTA dopamine neurons. Some of these input neurons normally activate the VTA by releasing a neurotransmitter called glutamate. However, the binding of endocannabinoids decreases their ability to do this, and thereby lowers the activation of the VTA dopamine neurons. But not all glutamate neurons are sensitive to endocannabinoids. Moreover, oxytocin affects glutamate neurons that fire repeatedly less than it affects those that fire only occasionally. Oxytocin thus acts as a filter. It allows certain inputs – those that are repeatedly active and those that are insensitive to endocannabinoids – to continue activating VTA dopamine neurons. At the same time, it weakens the influence of other inputs. Dopamine release in the VTA drives drug abuse and addiction. Understanding how oxytocin affects VTA neurons may thus open up new avenues for the treatment of addiction disorders.
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Affiliation(s)
- Lei Xiao
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Michael F Priest
- Department of Neurobiology, Northwestern University, Evanston, United States
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13
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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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14
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Zhang X, Liu S, Zhan F, Wang J, Jiang X. The Effects of Medium Spiny Neuron Morphologcial Changes on Basal Ganglia Network under External Electric Field: A Computational Modeling Study. Front Comput Neurosci 2017; 11:91. [PMID: 29123477 PMCID: PMC5662631 DOI: 10.3389/fncom.2017.00091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Accepted: 09/22/2017] [Indexed: 11/30/2022] Open
Abstract
The damage of dopaminergic neurons that innervate the striatum has been considered to be the proximate cause of Parkinson's disease (PD). In the dopamine-denervated state, the loss of dendritic spines and the decrease of dendritic length may prevent medium spiny neuron (MSN) from receiving too much excitatory stimuli from the cortex, thereby reducing the symptom of Parkinson's disease. However, the reduction in dendritic spine density obtained by different experiments is significantly different. We developed a biological-based network computational model to quantify the effect of dendritic spine loss and dendrites tree degeneration on basal ganglia (BG) signal regulation. Through the introduction of error index (EI), which was used to measure the attenuation of the signal, we explored the amount of dendritic spine loss and dendritic trees degradation required to restore the normal regulatory function of the network, and found that there were two ranges of dendritic spine loss that could reduce EI to normal levels in the case of dopamine at a certain level, this was also true for dendritic trees. However, although these effects were the same, the mechanisms of these two cases were significant difference. Using the method of phase diagram analysis, we gained insight into the mechanism of signal degradation. Furthermore, we explored the role of cortex in MSN morphology changes dopamine depletion-induced and found that proper adjustments to cortical activity do stop the loss in dendritic spines induced by dopamine depleted. These results suggested that modifying cortical drive onto MSN might provide a new idea on clinical therapeutic strategies for Parkinson's disease.
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Affiliation(s)
- Xiaohan Zhang
- Department of Mathematics, South China University of Technology, Guangzhou, China
| | - Shenquan Liu
- Department of Mathematics, South China University of Technology, Guangzhou, China
| | - Feibiao Zhan
- Department of Mathematics, South China University of Technology, Guangzhou, China
| | - Jing Wang
- Department of Mathematics, South China University of Technology, Guangzhou, China
| | - Xiaofang Jiang
- Department of Mathematics and Science, Henan Institute of Science and Technology, Xinxiang, China
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15
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Szűcs A, Rátkai A, Schlett K, Huerta R. Frequency-dependent regulation of intrinsic excitability by voltage-activated membrane conductances, computational modeling and dynamic clamp. Eur J Neurosci 2017; 46:2429-2444. [PMID: 28921695 DOI: 10.1111/ejn.13708] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 09/06/2017] [Accepted: 09/07/2017] [Indexed: 11/28/2022]
Abstract
As one of the most unique properties of nerve cells, their intrinsic excitability allows them to transform synaptic inputs into action potentials. This process reflects a complex interplay between the synaptic inputs and the voltage-dependent membrane currents of the postsynaptic neuron. While neurons in natural conditions mostly fire under the action of intense synaptic bombardment and receive fluctuating patterns of excitation and inhibition, conventional techniques to characterize intrinsic excitability mainly utilize static means of stimulation. Recently, we have shown that voltage-gated membrane currents regulate the firing responses under current step stimulation and under physiologically more realistic inputs in a differential manner. At the same time, a multitude of neuron types have been shown to exhibit some form of subthreshold resonance that potentially allows them to respond to synaptic inputs in a frequency-selective manner. In this study, we performed virtual experiments in computational models of neurons to examine how specific voltage-gated currents regulate their excitability under simulated frequency-modulated synaptic inputs. The model simulations and subsequent dynamic clamp experiments on mouse hippocampal pyramidal neurons revealed that the impact of voltage-gated currents in regulating the firing output is strongly frequency-dependent and mostly affecting the synaptic integration at theta frequencies. Notably, robust frequency-dependent regulation of intrinsic excitability was observed even when conventional analysis of membrane impedance suggested no such tendency. Consequently, plastic or homeostatic regulation of intrinsic membrane properties can tune the frequency selectivity of neuron populations in a way that is not readily expected from subthreshold impedance measurements.
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Affiliation(s)
- Attila Szűcs
- BioCircuits Institute, University of California San Diego, La Jolla, CA, USA.,MTA-ELTE-NAP B Neuronal Cell Biology Research Group, Eötvös Loránd University, 1/C Pázmány Péter Street, Budapest, H-1117, Hungary.,Balaton Limnological Institute of the Center for Ecological Research, Tihany, Hungary
| | - Anikó Rátkai
- MTA-ELTE-NAP B Neuronal Cell Biology Research Group, Eötvös Loránd University, 1/C Pázmány Péter Street, Budapest, H-1117, Hungary
| | - Katalin Schlett
- MTA-ELTE-NAP B Neuronal Cell Biology Research Group, Eötvös Loránd University, 1/C Pázmány Péter Street, Budapest, H-1117, Hungary
| | - Ramon Huerta
- BioCircuits Institute, University of California San Diego, La Jolla, CA, USA
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16
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Knowlton C, Kutterer S, Roeper J, Canavier CC. Calcium dynamics control K-ATP channel-mediated bursting in substantia nigra dopamine neurons: a combined experimental and modeling study. J Neurophysiol 2017; 119:84-95. [PMID: 28978764 DOI: 10.1152/jn.00351.2017] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Burst firing in medial substantia nigra (mSN) dopamine (DA) neurons has been selectively linked to novelty-induced exploration behavior in mice. Burst firing in mSN DA neurons, in contrast to lateral SN DA neurons, requires functional ATP-sensitive potassium (K-ATP) channels both in vitro and in vivo. However, the precise role of K-ATP channels in promoting burst firing is unknown. We show experimentally that L-type calcium channel activity in mSN DA neurons enhances open probability of K-ATP channels. We then generate a mathematical model to study the role of Ca2+ dynamics driving K-ATP channel function in mSN DA neurons during bursting. In our model, Ca2+ influx leads to local accumulation of ADP due to Ca-ATPase activity, which in turn activates K-ATP channels. If K-ATP channel activation reaches levels sufficient to terminate spiking, rhythmic bursting occurs. The model explains the experimental observation that, in vitro, coapplication of NMDA and a selective K-ATP channel opener, NN414, is required to elicit bursting as follows. Simulated NMDA receptor activation increases the firing rate and the rate of Ca2+ influx, which increases the activation of K-ATP. The model suggests that additional sources of hyperpolarization, such as GABAergic synaptic input, are recruited in vivo for burst termination or rebound burst discharge. The model predicts that NN414 increases the sensitivity of the K-ATP channel to ADP, promoting burst firing in vitro, and that that high levels of Ca2+ buffering, as might be expected in the calbindin-positive SN DA neuron subpopulation, promote rhythmic bursting pattern, consistent with experimental observations in vivo. NEW & NOTEWORTHY Recently identified distinct subpopulations of midbrain dopamine neurons exhibit differences in their two primary activity patterns in vivo: tonic (single spike) firing and phasic bursting. This study elucidates the biophysical basis of bursts specific to dopamine neurons in the medial substantia nigra, enabled by ATP-sensitive K+ channels and necessary for novelty-induced exploration. A better understanding of how dopaminergic signaling differs between subpopulations may lead to therapeutic strategies selectively targeted to specific subpopulations.
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Affiliation(s)
- Christopher Knowlton
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center , New Orleans, Louisiana
| | - Sylvie Kutterer
- Institut für Neurophysiologie, Goethe University , Frankfurt , Germany
| | - Jochen Roeper
- Institut für Neurophysiologie, Goethe University , Frankfurt , Germany
| | - Carmen C Canavier
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center , New Orleans, Louisiana
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17
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Levy KA, Brodnik ZD, Shaw JK, Perrey DA, Zhang Y, España RA. Hypocretin receptor 1 blockade produces bimodal modulation of cocaine-associated mesolimbic dopamine signaling. Psychopharmacology (Berl) 2017; 234:2761-2776. [PMID: 28667509 PMCID: PMC5709206 DOI: 10.1007/s00213-017-4673-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 06/06/2017] [Indexed: 02/07/2023]
Abstract
RATIONALE Cocaine addiction is a chronic psychiatric disorder characterized by pathological motivation to obtain cocaine and behavioral and neurochemical hypersensitivity to cocaine-associated cues. These features of cocaine addiction are thought to be driven by aberrant phasic dopamine signaling. We previously demonstrated that blockade of the hypocretin receptor 1 (HCRTr1) attenuates cocaine self-administration and reduces cocaine-induced enhancement of dopamine signaling. Despite this evidence, the effects of HCRTr1 blockade on endogenous phasic dopamine release are unknown. OBJECTIVE In the current studies, we assessed whether blockade of HCRTr1 alters spontaneous and cue-evoked dopamine release in the nucleus accumbens core of freely moving rats. METHODS We first validated the behavioral and neurochemical effects of the novel, highly selective, HCRTr1 antagonist RTIOX-276 using cocaine self-administration and fast-scan cyclic voltammetry (FSCV) in anesthetized rats. We then used FSCV in freely moving rats to examine whether RTIOX-276 impacts spontaneous and cue-evoked dopamine release. Finally, we used ex vivo slice FSCV to determine whether the effects of RTIOX-276 on dopamine signaling involve dopamine terminal adaptations. RESULTS Doses of RTIOX-276 that attenuate the motivation for cocaine reduce spontaneous dopamine transient amplitude and cue-evoked dopamine release. Further, these doses attenuated cocaine-induced dopamine uptake inhibition at the level of dopamine terminals. CONCLUSION Our results provide support for the standing hypothesis that HCRTr1 blockade suppresses endogenous phasic dopamine signals, likely via actions at dopamine cell bodies. These results also elucidate a second process through which HCRTr1 blockade attenuates the effects of cocaine by reducing cocaine sensitivity at dopamine terminals.
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Affiliation(s)
- KA Levy
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, U.S.A
| | - ZD Brodnik
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, U.S.A
| | - JK Shaw
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, U.S.A
| | - DA Perrey
- Research Triangle Institute, Research Triangle Park, North Carolina 27709, U.S.A
| | - Y Zhang
- Research Triangle Institute, Research Triangle Park, North Carolina 27709, U.S.A
| | - RA España
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, U.S.A
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18
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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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19
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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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20
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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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21
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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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22
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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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23
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Enrico P, Migliore M, Spiga S, Mulas G, Caboni F, Diana M. Morphofunctional alterations in ventral tegmental area dopamine neurons in acute and prolonged opiates withdrawal. A computational perspective. Neuroscience 2016; 322:195-207. [DOI: 10.1016/j.neuroscience.2016.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 01/14/2016] [Accepted: 02/02/2016] [Indexed: 11/28/2022]
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24
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Paladini C, Tepper J. Neurophysiology of Substantia Nigra Dopamine Neurons: Modulation by GABA and Glutamate. HANDBOOK OF BEHAVIORAL NEUROSCIENCE 2016. [DOI: 10.1016/b978-0-12-802206-1.00017-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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25
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Pignatelli M, Bonci A. Role of Dopamine Neurons in Reward and Aversion: A Synaptic Plasticity Perspective. Neuron 2015; 86:1145-57. [PMID: 26050034 DOI: 10.1016/j.neuron.2015.04.015] [Citation(s) in RCA: 172] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The brain is wired to predict future outcomes. Experience-dependent plasticity at excitatory synapses within dopamine neurons of the ventral tegmental area, a key region for a broad range of motivated behaviors, is thought to be a fundamental cellular mechanism that enables adaptation to a dynamic environment. Thus, depending on the circumstances, dopamine neurons are capable of processing both positive and negative reinforcement learning strategies. In this review, we will discuss how changes in synaptic plasticity of dopamine neurons may affect dopamine release, as well as behavioral adaptations to different environmental conditions falling at opposite ends of a saliency spectrum ranging from reward to aversion.
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Affiliation(s)
- Marco Pignatelli
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA
| | - Antonello Bonci
- Intramural Research Program, Synaptic Plasticity Section, National Institute on Drug Abuse, Baltimore, MD 21224, USA; Solomon H. Snyder Neuroscience Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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26
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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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27
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de Kloet SF, Mansvelder HD, De Vries TJ. Cholinergic modulation of dopamine pathways through nicotinic acetylcholine receptors. Biochem Pharmacol 2015. [PMID: 26208783 DOI: 10.1016/j.bcp.2015.07.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Nicotine addiction is highly prevalent in current society and is often comorbid with other diseases. In the central nervous system, nicotine acts as an agonist for nicotinic acetylcholine receptors (nAChRs) and its effects depend on location and receptor composition. Although nicotinic receptors are found in most brain regions, many studies on addiction have focused on the mesolimbic system and its reported behavioral correlates such as reward processing and reinforcement learning. Profound modulatory cholinergic input from the pedunculopontine and laterodorsal tegmentum to dopaminergic midbrain nuclei as well as local cholinergic interneuron projections to dopamine neuron axons in the striatum may play a major role in the effects of nicotine. Moreover, an indirect mesocorticolimbic feedback loop involving the medial prefrontal cortex may be involved in behavioral characteristics of nicotine addiction. Therefore, this review will highlight current understanding of the effects of nicotine on the function of mesolimbic and mesocortical dopamine projections in the mesocorticolimbic circuit.
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Affiliation(s)
- Sybren F de Kloet
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
| | - Huibert D Mansvelder
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands.
| | - Taco J De Vries
- Department of Molecular and Cellular Neurobiology, Center for Neurogenomics and Cogntive Research (CNCR), Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands; Department of Anatomy and Neurosciences, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
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Yu N, Canavier CC. A Mathematical Model of a Midbrain Dopamine Neuron Identifies Two Slow Variables Likely Responsible for Bursts Evoked by SK Channel Antagonists and Terminated by Depolarization Block. JOURNAL OF MATHEMATICAL NEUROSCIENCE 2015; 5:5. [PMID: 25852980 PMCID: PMC4385104 DOI: 10.1186/s13408-015-0017-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 02/03/2015] [Indexed: 06/04/2023]
Abstract
Midbrain dopamine neurons exhibit a novel type of bursting that we call "inverted square wave bursting" when exposed to Ca(2+)-activated small conductance (SK) K(+) channel blockers in vitro. This type of bursting has three phases: hyperpolarized silence, spiking, and depolarization block. We find that two slow variables are required for this type of bursting, and we show that the three-dimensional bifurcation diagram for inverted square wave bursting is a folded surface with upper (depolarized) and lower (hyperpolarized) branches. The activation of the L-type Ca(2+) channel largely supports the separation between these branches. Spiking is initiated at a saddle node on an invariant circle bifurcation at the folded edge of the lower branch and the trajectory spirals around the unstable fixed points on the upper branch. Spiking is terminated at a supercritical Hopf bifurcation, but the trajectory remains on the upper branch until it hits a saddle node on the upper folded edge and drops to the lower branch. The two slow variables contribute as follows. A second, slow component of sodium channel inactivation is largely responsible for the initiation and termination of spiking. The slow activation of the ether-a-go-go-related (ERG) K(+) current is largely responsible for termination of the depolarized plateau. The mechanisms and slow processes identified herein may contribute to bursting as well as entry into and recovery from the depolarization block to different degrees in different subpopulations of dopamine neurons in vivo.
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Affiliation(s)
- Na Yu
- />Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA 70112 USA
- />Department of Mathematics and Computer Science, Lawrence Technological University, 21000 West 10 Mile Road, Southfield, MI 48075 USA
| | - Carmen C. Canavier
- />Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA 70112 USA
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WANG LEI, LIANG PEIJI, ZHANG PUMING, QIU YIHONG. ADAPTATION-DEPENDENT SYNCHRONIZATION TRANSITIONS AND BURST GENERATIONS IN ELECTRICALLY COUPLED NEURAL NETWORKS. Int J Neural Syst 2014; 24:1450033. [DOI: 10.1142/s0129065714500336] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A typical feature of neurons is their ability to encode neural information dynamically through spike frequency adaptation (SFA). Previous studies of SFA on neuronal synchronization were mainly concentrated on the correlated firing between neuron pairs, while the synchronization of neuron populations in the presence of SFA is still unclear. In this study, the influence of SFA on the population synchronization of neurons was numerically explored in electrically coupled networks, with regular, small-world, and random connectivity, respectively. The simulation results indicate that cross-correlation indices decrease significantly when the neurons have adaptation compared with those of nonadapting neurons, similar to previous experimental observations. However, the synchronous activity of population neurons exhibits a rather complex adaptation-dependent manner. Specifically, synchronization strength of neuron populations changes nonmonotonically, depending on the degree of adaptation. In addition, single neurons in the networks can switch from regular spiking to bursting with the increase of adaptation degree. Furthermore, the connection probability among neurons exhibits significant influence on the population synchronous activity, but has little effect on the burst generation of single neurons. Accordingly, the results may suggest that synchronous activity and burst firing of population neurons are both adaptation-dependent.
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Affiliation(s)
- LEI WANG
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - PEI-JI LIANG
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - PU-MING ZHANG
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - YI-HONG QIU
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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Qian K, Yu N, Tucker KR, Levitan ES, Canavier CC. Mathematical analysis of depolarization block mediated by slow inactivation of fast sodium channels in midbrain dopamine neurons. J Neurophysiol 2014; 112:2779-90. [PMID: 25185810 DOI: 10.1152/jn.00578.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dopamine neurons in freely moving rats often fire behaviorally relevant high-frequency bursts, but depolarization block limits the maximum steady firing rate of dopamine neurons in vitro to ∼10 Hz. Using a reduced model that faithfully reproduces the sodium current measured in these neurons, we show that adding an additional slow component of sodium channel inactivation, recently observed in these neurons, qualitatively changes in two different ways how the model enters into depolarization block. First, the slow time course of inactivation allows multiple spikes to be elicited during a strong depolarization prior to entry into depolarization block. Second, depolarization block occurs near or below the spike threshold, which ranges from -45 to -30 mV in vitro, because the additional slow component of inactivation negates the sodium window current. In the absence of the additional slow component of inactivation, this window current produces an N-shaped steady-state current-voltage (I-V) curve that prevents depolarization block in the experimentally observed voltage range near -40 mV. The time constant of recovery from slow inactivation during the interspike interval limits the maximum steady firing rate observed prior to entry into depolarization block. These qualitative features of the entry into depolarization block can be reversed experimentally by replacing the native sodium conductance with a virtual conductance lacking the slow component of inactivation. We show that the activation of NMDA and AMPA receptors can affect bursting and depolarization block in different ways, depending upon their relative contributions to depolarization versus to the total linear/nonlinear conductance.
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Affiliation(s)
- Kun Qian
- Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, Louisiana; Neuroscience Center of Excellence, Louisiana State University School of Medicine, New Orleans, Louisiana; and
| | - Na Yu
- Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, Louisiana
| | - Kristal R Tucker
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Edwin S Levitan
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Carmen C Canavier
- Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, Louisiana; Neuroscience Center of Excellence, Louisiana State University School of Medicine, New Orleans, Louisiana; and
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31
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Feng SS, Lin R, Gauck V, Jaeger D. Gain control of synaptic response function in cerebellar nuclear neurons by a calcium-activated potassium conductance. THE CEREBELLUM 2014; 12:692-706. [PMID: 23605187 DOI: 10.1007/s12311-013-0476-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Small conductance Ca(2+)-activated potassium (SK) current provides an important modulator of excitatory synaptic transmission, which undergoes plastic regulation via multiple mechanisms. We examined whether inhibitory input processing is also dependent on SK current in the cerebellar nuclei (CN) where inhibition provides the only route of information transfer from the cerebellar cortical Purkinje cells. We employed dynamic clamping in conjunction with computer simulations to address this question. We found that SK current plays a critical role in the inhibitory synaptic control of spiking output. Specifically, regulation of SK current density resulted in a gain control of spiking output, such that low SK current promoted large output signaling for large inhibitory cell input fluctuations due to Purkinje cell synchronization. In contrast, smaller nonsynchronized Purkinje cell input fluctuations were not amplified. Regulation of SK density in the CN therefore would likely lead to important consequences for the transmission of synchronized Purkinje cell activity to the motor system.
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Affiliation(s)
- Steven Si Feng
- Department of Biology, Emory University, 1510 Clifton Rd., Atlanta, GA, 30322, USA
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32
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Nair AG, Gutierrez-Arenas O, Eriksson O, Jauhiainen A, Blackwell KT, Kotaleski JH. Modeling intracellular signaling underlying striatal function in health and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:277-304. [PMID: 24560149 DOI: 10.1016/b978-0-12-397897-4.00013-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Striatum, which is the input nucleus of the basal ganglia, integrates cortical and thalamic glutamatergic inputs with dopaminergic afferents from the substantia nigra pars compacta. The combination of dopamine and glutamate strongly modulates molecular and cellular properties of striatal neurons and the strength of corticostriatal synapses. These actions are performed via intracellular signaling networks, containing several intertwined feedback loops. Understanding the role of dopamine and other neuromodulators requires the development of quantitative dynamical models for describing the intracellular signaling, in order to provide precise unambiguous descriptions and quantitative predictions. Building such models requires integration of data from multiple data sources containing information regarding the molecular interactions, the strength of these interactions, and the subcellular localization of the molecules. Due to the uncertainty, variability, and sparseness of these data, parameter estimation techniques are critical for inferring or constraining the unknown parameters, and sensitivity analysis evaluates which parameters are most critical for a given observed macroscopic behavior. Here, we briefly review the modeling approaches and tools that have been used to investigate biochemical signaling in the striatum, along with some of the models built around striatum. We also suggest a future direction for the development of such models from the, now becoming abundant, high-throughput data.
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Affiliation(s)
- Anu G Nair
- School of Computer Science and Communication, Royal Institute of Technology, Stockholm, Sweden
| | - Omar Gutierrez-Arenas
- School of Computer Science and Communication, Royal Institute of Technology, Stockholm, Sweden
| | - Olivia Eriksson
- Department of Numerical Analysis and Computer Science, Stockholm University, Stockholm, Sweden
| | - Alexandra Jauhiainen
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Kim T Blackwell
- Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA, USA
| | - Jeanette H Kotaleski
- School of Computer Science and Communication, Royal Institute of Technology, Stockholm, Sweden; Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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Ha J, Kuznetsov A. Interaction of NMDA receptor and pacemaking mechanisms in the midbrain dopaminergic neuron. PLoS One 2013; 8:e69984. [PMID: 23894569 PMCID: PMC3716766 DOI: 10.1371/journal.pone.0069984] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 06/14/2013] [Indexed: 11/18/2022] Open
Abstract
Dopamine neurotransmission has been found to play a role in addictive behavior and is altered in psychiatric disorders. Dopaminergic (DA) neurons display two functionally distinct modes of electrophysiological activity: low- and high-frequency firing. A puzzling feature of the DA neuron is the following combination of its responses: N-methyl-D-aspartate receptor (NMDAR) activation evokes high-frequency firing, whereas other tonic excitatory stimuli (α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate receptor (AMPAR) activation or applied depolarization) block firing instead. We suggest a new computational model that reproduces this combination of responses and explains recent experimental data. Namely, somatic NMDAR stimulation evokes high-frequency firing and is more effective than distal dendritic stimulation. We further reduce the model to a single compartment and analyze the mechanism of the distinct high-frequency response to NMDAR activation vs. other stimuli. Standard nullcline analysis shows that the mechanism is based on a decrease in the amplitude of calcium oscillations. The analysis confirms that the nonlinear voltage dependence provided by the magnesium block of the NMDAR determine its capacity to elevate the firing frequency. We further predict that the moderate slope of the voltage dependence plays the central role in the frequency elevation. Additionally, we suggest a repolarizing current that sustains calcium-independent firing or firing in the absence of calcium-dependent repolarizing currents. We predict that the ether-a-go-go current (ERG), which has been observed in the DA neuron, is the best fit for this critical role. We show that a calcium-dependent and a calcium-independent oscillatory mechanisms form a structure of interlocked negative feedback loops in the DA neuron. The structure connects research of DA neuron firing with circadian biology and determines common minimal models for investigation of robustness of oscillations, which is critical for normal function of both systems.
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Affiliation(s)
- Joon Ha
- Laboratory of Biological Modeling, The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institute of Health, Bethesda, Maryland, United States of America
| | - Alexey Kuznetsov
- Department of Mathematical Sciences and Center for Mathematical Biosciences, Indiana University, Purdue University Indianapolis, Indianapolis, Indiana, United States of America
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Francis F, García MR, Middleton RH. A single compartment model of pacemaking in dissasociated substantia nigra neurons: stability and energy analysis. J Comput Neurosci 2013; 35:295-316. [PMID: 23686304 DOI: 10.1007/s10827-013-0453-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 04/01/2013] [Accepted: 04/03/2013] [Indexed: 01/08/2023]
Abstract
Spontaneous oscillations in the mid-brain dopaminergic neurons are an important feature of motor control. The degeneration of these neurons is involved in movement disorders, particularly Parkinson's Disease. Modelling of this activity is an important part of developing an understanding of the pathogenic process. We develop a mathematical paradigm to describe this activity with a single compartment approach and a CellML version is made publicly available. The model explicitly describes the dynamics of the transmembrane potential with changes in the levels of important cations and is consistent with two major observations in the literature regarding its behaviour in the presence of channel blockers. Stability of the model behaviour is determined from the properties of its Monodromy matrix. We also discuss from the perspective of energy, a pharmacological intervention suggested in the treatment of Parkinson's Disease.
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Affiliation(s)
- Febe Francis
- Hamilton Institute, NUI Maynooth, Co. Kildare, Ireland
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35
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Tolu S, Eddine R, Marti F, David V, Graupner M, Pons S, Baudonnat M, Husson M, Besson M, Reperant C, Zemdegs J, Pagès C, Hay YAH, Lambolez B, Caboche J, Gutkin B, Gardier AM, Changeux JP, Faure P, Maskos U. Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement. Mol Psychiatry 2013; 18:382-93. [PMID: 22751493 DOI: 10.1038/mp.2012.83] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or γ-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.
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Affiliation(s)
- S Tolu
- Département de Neuroscience, Institut Pasteur, Unité Neurobiologie intégrative des systèmes cholinergiques, Paris, France
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36
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Drion G, Franci A, Seutin V, Sepulchre R. A novel phase portrait for neuronal excitability. PLoS One 2012; 7:e41806. [PMID: 22905107 PMCID: PMC3414513 DOI: 10.1371/journal.pone.0041806] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 06/25/2012] [Indexed: 12/04/2022] Open
Abstract
Fifty years ago, FitzHugh introduced a phase portrait that became famous for a twofold reason: it captured in a physiological way the qualitative behavior of Hodgkin-Huxley model and it revealed the power of simple dynamical models to unfold complex firing patterns. To date, in spite of the enormous progresses in qualitative and quantitative neural modeling, this phase portrait has remained a core picture of neuronal excitability. Yet, a major difference between the neurophysiology of 1961 and of 2011 is the recognition of the prominent role of calcium channels in firing mechanisms. We show that including this extra current in Hodgkin-Huxley dynamics leads to a revision of FitzHugh-Nagumo phase portrait that affects in a fundamental way the reduced modeling of neural excitability. The revisited model considerably enlarges the modeling power of the original one. In particular, it captures essential electrophysiological signatures that otherwise require non-physiological alteration or considerable complexification of the classical model. As a basic illustration, the new model is shown to highlight a core dynamical mechanism by which calcium channels control the two distinct firing modes of thalamocortical neurons.
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Affiliation(s)
- Guillaume Drion
- Neurophysiology Unit and GIGA Neurosciences, University of Liège, Liège, Belgium
- Department of Electrical Engineering and Computer Science and GIGA Research, University of Liège, Liège, Belgium
| | | | - Vincent Seutin
- Neurophysiology Unit and GIGA Neurosciences, University of Liège, Liège, Belgium
| | - Rodolphe Sepulchre
- Department of Electrical Engineering and Computer Science and GIGA Research, University of Liège, Liège, Belgium
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37
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Jeong J, Shi WX, Hoffman R, Oh J, Gore JC, Bunney BS, Peterson BS. Bursting as a source of non-linear determinism in the firing patterns of nigral dopamine neurons. Eur J Neurosci 2012; 36:3214-23. [PMID: 22831464 DOI: 10.1111/j.1460-9568.2012.08238.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nigral dopamine (DA) neurons in vivo exhibit complex firing patterns consisting of tonic single-spikes and phasic bursts that encode information for certain types of reward-related learning and behavior. Non-linear dynamical analysis has previously demonstrated the presence of a non-linear deterministic structure in complex firing patterns of DA neurons, yet the origin of this non-linear determinism remains unknown. In this study, we hypothesized that bursting activity is the primary source of non-linear determinism in the firing patterns of DA neurons. To test this hypothesis, we investigated the dimension complexity of inter-spike interval data recorded in vivo from bursting and non-bursting DA neurons in the chloral hydrate-anesthetized rat substantia nigra. We found that bursting DA neurons exhibited non-linear determinism in their firing patterns, whereas non-bursting DA neurons showed truly stochastic firing patterns. Determinism was also detected in the isolated burst and inter-burst interval data extracted from firing patterns of bursting neurons. Moreover, less bursting DA neurons in halothane-anesthetized rats exhibited higher dimensional spiking dynamics than do more bursting DA neurons in chloral hydrate-anesthetized rats. These results strongly indicate that bursting activity is the main source of low-dimensional, non-linear determinism in the firing patterns of DA neurons. This finding furthermore suggests that bursts are the likely carriers of meaningful information in the firing activities of DA neurons.
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Affiliation(s)
- Jaeseung Jeong
- Department of Psychiatry, Columbia College of Physicians and Surgeons, New York, NY, USA.
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38
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Harrington MG, Chekmenev EY, Schepkin V, Fonteh AN, Arakaki X. Sodium MRI in a rat migraine model and a NEURON simulation study support a role for sodium in migraine. Cephalalgia 2011; 31:1254-65. [PMID: 21816771 DOI: 10.1177/0333102411408360] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
INTRODUCTION Increased lumbar cerebrospinal fluid (CSF) sodium has been reported during migraine. We used ultra-high field MRI to investigate cranial sodium in a rat migraine model, and simulated the effects of extracellular sodium on neuronal excitability. METHODS Behavioral changes in the nitroglycerin (NTG) rat migraine model were determined from von Frey hair withdrawal response and photography. Central sensitization was measured by counting cFos-immunoreactive cells in the trigeminal nucleus caudalis (TNC). Sodium was quantified in vivo by ultra-high field sodium MRI at 21 Tesla. Effects of extracellular sodium on neuronal excitability were modeled using NEURON software. RESULTS NTG decreased von Frey withdrawal threshold (p=0.0003), decreased eyelid vertical height:width ratio (p<0.0001), increased TNC cFos stain (p<0.0001), and increased sodium between 7.5 and 17% in brain, intracranial CSF, and vitreous humor (p<0.05). Simulated neurons exposed to higher sodium have more frequent and earlier spontaneous action potentials, and corresponding earlier sodium and potassium currents. CONCLUSIONS In the rat migraine model, sodium rises to levels that increase neuronal excitability. We propose that rising sodium in CSF surrounding trigeminal nociceptors increases their excitability and causes pain and that rising sodium in vitreous humor increases retinal neuronal excitability and causes photosensitivity.
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Affiliation(s)
- Michael G Harrington
- Molecular Neurology Program, Huntington Medical Research Institutes, 99 North El Molino Avenue, Pasadena, CA 91101, USA.
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39
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Drion G, Massotte L, Sepulchre R, Seutin V. How modeling can reconcile apparently discrepant experimental results: the case of pacemaking in dopaminergic neurons. PLoS Comput Biol 2011; 7:e1002050. [PMID: 21637742 PMCID: PMC3102759 DOI: 10.1371/journal.pcbi.1002050] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Accepted: 03/28/2011] [Indexed: 11/23/2022] Open
Abstract
Midbrain dopaminergic neurons are endowed with endogenous slow pacemaking properties. In recent years, many different groups have studied the basis for this phenomenon, often with conflicting conclusions. In particular, the role of a slowly-inactivating L-type calcium channel in the depolarizing phase between spikes is controversial, and the analysis of slow oscillatory potential (SOP) recordings during the blockade of sodium channels has led to conflicting conclusions. Based on a minimal model of a dopaminergic neuron, our analysis suggests that the same experimental protocol may lead to drastically different observations in almost identical neurons. For example, complete L-type calcium channel blockade eliminates spontaneous firing or has almost no effect in two neurons differing by less than 1% in their maximal sodium conductance. The same prediction can be reproduced in a state of the art detailed model of a dopaminergic neuron. Some of these predictions are confirmed experimentally using single-cell recordings in brain slices. Our minimal model exhibits SOPs when sodium channels are blocked, these SOPs being uncorrelated with the spiking activity, as has been shown experimentally. We also show that block of a specific conductance (in this case, the SK conductance) can have a different effect on these two oscillatory behaviors (pacemaking and SOPs), despite the fact that they have the same initiating mechanism. These results highlight the fact that computational approaches, besides their well known confirmatory and predictive interests in neurophysiology, may also be useful to resolve apparent discrepancies between experimental results. Dopamine is a neurotransmitter which plays important roles in the control of voluntary movement, motivation and reward, attention, and learning. Dysfunction of midbrain dopaminergic systems is involved in various diseases such as Parkinson's disease, schizophrenia and drug abuse. This underlines the importance of a tight regulation of dopamine levels in the brain. At the cellular level, the release of dopamine is directly correlated to the type of electrical activity (the firing pattern) of nerve cells that produce it, the so-called “dopaminergic neurons”. Therefore, an in depth understanding of the mechanisms underlying the electrical behavior of dopaminergic neurons is of critical importance to find new strategies for the treatment of diseases that result from dysfunction of this system.
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Affiliation(s)
- Guillaume Drion
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
- Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Laurent Massotte
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
| | - Rodolphe Sepulchre
- Department of Electrical Engineering and Computer Science, University of Liège, Liège, Belgium
| | - Vincent Seutin
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Liège, Belgium
- * E-mail:
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40
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Drion G, Bonjean M, Waroux O, Scuvée-Moreau J, Liégeois JF, Sejnowski TJ, Sepulchre R, Seutin V. M-type channels selectively control bursting in rat dopaminergic neurons. Eur J Neurosci 2010; 31:827-35. [PMID: 20180842 PMCID: PMC2861736 DOI: 10.1111/j.1460-9568.2010.07107.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Midbrain dopaminergic neurons in the substantia nigra, pars compacta and ventral tegmental area are critically important in many physiological functions. These neurons exhibit firing patterns that include tonic slow pacemaking, irregular firing and bursting, and the amount of dopamine that is present in the synaptic cleft is much increased during bursting. The mechanisms responsible for the switch between these spiking patterns remain unclear. Using both in-vivo recordings combined with microiontophoretic or intraperitoneal drug applications and in-vitro experiments, we have found that M-type channels, which are present in midbrain dopaminergic cells, modulate the firing during bursting without affecting the background low-frequency pacemaker firing. Thus, a selective blocker of these channels, 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride, specifically potentiated burst firing. Computer modeling of the dopamine neuron confirmed the possibility of a differential influence of M-type channels on excitability during various firing patterns. Therefore, these channels may provide a novel target for the treatment of dopamine-related diseases, including Parkinson’s disease and drug addiction. Moreover, our results demonstrate that the influence of M-type channels on the excitability of these slow pacemaker neurons is conditional upon their firing pattern.
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Affiliation(s)
- Guillaume Drion
- Laboratory of Pharmacology and GIGA Neurosciences, University of Liège, Belgium
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41
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Kuznetsova AY, Huertas MA, Kuznetsov AS, Paladini CA, Canavier CC. Regulation of firing frequency in a computational model of a midbrain dopaminergic neuron. J Comput Neurosci 2010; 28:389-403. [PMID: 20217204 DOI: 10.1007/s10827-010-0222-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 01/15/2010] [Accepted: 02/01/2010] [Indexed: 11/25/2022]
Abstract
Dopaminergic (DA) neurons of the mammalian midbrain exhibit unusually low firing frequencies in vitro. Furthermore, injection of depolarizing current induces depolarization block before high frequencies are achieved. The maximum steady and transient rates are about 10 and 20 Hz, respectively, despite the ability of these neurons to generate bursts at higher frequencies in vivo. We use a three-compartment model calibrated to reproduce DA neuron responses to several pharmacological manipulations to uncover mechanisms of frequency limitation. The model exhibits a slow oscillatory potential (SOP) dependent on the interplay between the L-type Ca(2+) current and the small conductance K(+) (SK) current that is unmasked by fast Na(+) current block. Contrary to previous theoretical work, the SOP does not pace the steady spiking frequency in our model. The main currents that determine the spontaneous firing frequency are the subthreshold L-type Ca(2+) and the A-type K(+) currents. The model identifies the channel densities for the fast Na(+) and the delayed rectifier K(+) currents as critical parameters limiting the maximal steady frequency evoked by a depolarizing pulse. We hypothesize that the low maximal steady frequencies result from a low safety factor for action potential generation. In the model, the rate of Ca(2+) accumulation in the distal dendrites controls the transient initial frequency in response to a depolarizing pulse. Similar results are obtained when the same model parameters are used in a multi-compartmental model with a realistic reconstructed morphology, indicating that the salient contributions of the dendritic architecture have been captured by the simpler model.
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Affiliation(s)
- Anna Y Kuznetsova
- Department of Biology and Neurosciences Institute, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA
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42
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Neuroplastic alterations in the limbic system following cocaine or alcohol exposure. Curr Top Behav Neurosci 2010; 3:3-27. [PMID: 21161748 DOI: 10.1007/7854_2009_23] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Neuroplastic changes in the CNS are thought to be a fundamental component of learning and memory. While pioneering studies in the hippocampus and cerebellum have detailed many of the basic mechanisms that can lead to alterations in synaptic transmission based on previous activity, only more recently has synaptic plasticity been monitored after behavioral manipulation or drug exposure. In this chapter, we review evidence that drugs of abuse are powerful modulators of synaptic plasticity. Both the dopaminergic neurons of the ventral tegmental area as well medium spiny neurons in nucleus accumbens show enhanced excitatory synaptic strength following passive or active exposure to drugs such as cocaine and alcohol. In the VTA, both the enhancement of excitatory synaptic strength and the acquisition of drug-related behaviors depend on signaling through the N-methyl-D: -aspartate receptors (NMDARs) which are mechanistically thought to lead to increased synaptic insertion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). Synaptic insertion of AMPARs by drugs of abuse can be long lasting, depending on the route of administration, number of drug exposures, or whether the drugs are received passively or self-administered.
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Bonci A, Borgland S. Role of orexin/hypocretin and CRF in the formation of drug-dependent synaptic plasticity in the mesolimbic system. Neuropharmacology 2009; 56 Suppl 1:107-11. [DOI: 10.1016/j.neuropharm.2008.07.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 07/10/2008] [Accepted: 07/17/2008] [Indexed: 10/21/2022]
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Chen BT, Bowers MS, Martin M, Hopf FW, Guillory AM, Carelli RM, Chou JK, Bonci A. Cocaine but not natural reward self-administration nor passive cocaine infusion produces persistent LTP in the VTA. Neuron 2008; 59:288-97. [PMID: 18667156 DOI: 10.1016/j.neuron.2008.05.024] [Citation(s) in RCA: 229] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Revised: 03/28/2008] [Accepted: 05/20/2008] [Indexed: 10/21/2022]
Abstract
Persistent drug-seeking behavior is hypothesized to co-opt the brain's natural reward-motivational system. Although ventral tegmental area (VTA) dopamine (DA) neurons represent a crucial component of this system, the synaptic adaptations underlying natural rewards and drug-related motivation have not been fully elucidated. Here, we show that self-administration of cocaine, but not passive cocaine infusions, produced a persistent potentiation of VTA excitatory synapses, which was still present after 3 months abstinence. Further, enhanced synaptic function in VTA was evident even after 3 weeks of extinction training. Food or sucrose self-administration induced only a transient potentiation of VTA glutamatergic signaling. Our data show that synaptic function in VTA DA neurons is readily but reversibly enhanced by natural reward-seeking behavior, while voluntary cocaine self-administration induced a persistent synaptic enhancement that is resistant to behavioral extinction. Such persistent synaptic potentiation in VTA DA neurons may represent a fundamental cellular phenomenon driving pathological drug-seeking behavior.
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Affiliation(s)
- Billy T Chen
- Ernest Gallo Clinic and Research Center, Department of Neurology, University of California, San Francisco, Emeryville, CA 94608, USA
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Stuber GD, Hopf FW, Hahn J, Cho SL, Guillory A, Bonci A. Voluntary ethanol intake enhances excitatory synaptic strength in the ventral tegmental area. Alcohol Clin Exp Res 2008; 32:1714-20. [PMID: 18627359 DOI: 10.1111/j.1530-0277.2008.00749.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Addiction has been considered a disorder of motivational control over behavior, and the ventral tegmental area (VTA), in conjunction with other limbic brain structures, is thought to play a critical role in the regulation of a number of motivated behaviors including seeking of addictive drugs such as alcohol. Of particular interest is the ability of prolonged exposure of addictive drugs to enhance the function of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamatergic receptors (AMPAR) in the VTA, as glutamate receptor activation can significantly regulate VTA neuron activity. Here, we examined whether voluntary ethanol intake altered VTA AMPAR function. METHODS We utilized in vitro electrophysiology to examine glutamatergic function in the VTA neurons 12 to 24 hours after the last self-administration bout, which occurred 35 to 50 days after the initiation of ethanol self-administration under a 2-bottle intermittent access model. RESULTS Voluntary intermittent ethanol intake in a 2-bottle paradigm enhanced postsynaptic AMPAR function, indicated by an increased ratio of evoked AMPAR to N-methyl-d-aspartic acid receptor currents, and by an increase in the amplitude of spontaneous miniature excitatory postsynaptic currents (mEPSCs) measured in the presence of tetrodotoxin to prevent action potential-dependent release. In contrast, ethanol self-administration did not alter evoked presynaptic glutamate release, indicated by no change in the paired-pulse ratio of 2 AMPAR EPSCs evoked 50 ms apart, although spontaneous glutamate release was significantly enhanced, indicated by enhanced mEPSC frequency. CONCLUSIONS Our results suggest that postsynaptic AMPAR function in VTA neurons was significantly enhanced after ethanol self-administration. As increased VTA AMPAR function can significantly regulate firing and enhance the reinforcing and activating effects of drugs of abuse, the increased AMPAR activity observed here may facilitate the drive to consume ethanol.
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Affiliation(s)
- Garret D Stuber
- Department of Neurology, Ernest Gallo Clinic and Research Center, University of California at San Francisco, Emeryville, California 94608, USA
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Migliore M, Cannia C, Canavier CC. A Modeling Study Suggesting a Possible Pharmacological Target to Mitigate the Effects of Ethanol on Reward-Related Dopaminergic Signaling. J Neurophysiol 2008; 99:2703-7. [DOI: 10.1152/jn.00024.2008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Midbrain dopaminergic neurons are involved in several critical brain functions controlling goal-directed behaviors, reinforcing/reward processes, and motivation. Their dysfunctions alter dopamine release and contribute to a vast range of neural disorders, from Parkinson's disease to schizophrenia and addictive behaviors. These neurons have thus been a natural target of pharmacological treatments trying to ameliorate the consequences of several neuropathologies. From this point of view, a clear experimental link has been recently established between the increase in the pacemaker frequency of dopaminergic neurons in vitro after acute ethanol application and a particular ionic current ( Ih). The functional consequences in vivo, however, are not clear and they are very difficult to explore experimentally. Here we use a realistic computational model of dopaminergic neurons in vivo to suggest that ethanol, through its effects on Ih, modifies the temporal structure of the spiking activity. The model predicts that the dopamine level may increase much more during bursting than during pacemaking activity, especially in those brain regions with a slow dopamine clearance rate. The results suggest that a selective pharmacological remedy could thus be devised against the rewarding effects of ethanol that are postulated to mediate alcohol abuse and addiction, targeting the specific HCN genes expressed in dopaminergic neurons.
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