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Rawal B, Rancic V, Ballanyi K. NMDA Enhances and Glutamate Attenuates Synchrony of Spontaneous Phase-Locked Locus Coeruleus Network Rhythm in Newborn Rat Brain Slices. Brain Sci 2022; 12:brainsci12050651. [PMID: 35625039 PMCID: PMC9140167 DOI: 10.3390/brainsci12050651] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/05/2022] [Accepted: 05/12/2022] [Indexed: 01/27/2023] Open
Abstract
Locus coeruleus (LC) neurons are controlled by glutamatergic inputs. Here, we studied in brain slices of neonatal rats NMDA and glutamate effects on phase-locked LC neuron spiking at ~1 Hz summating to ~0.2 s-lasting bell-shaped local field potential (LFP). NMDA: 10 μM accelerated LFP 1.7-fold, whereas 25 and 50 μM, respectively, increased its rate 3.2- and 4.6-fold while merging discrete events into 43 and 56% shorter oscillations. After 4–6 min, LFP oscillations stopped every 6 s for 1 s, resulting in ‘oscillation trains’. A dose of 32 μM depolarized neurons by 8.4 mV to cause 7.2-fold accelerated spiking at reduced jitter and enhanced synchrony with the LFP, as evident from cross-correlation. Glutamate: 25–50 μM made rhythm more irregular and the LFP pattern could transform into 2.7-fold longer-lasting multipeak discharge. In 100 μM, LFP amplitude and duration declined. In 25–50 μM, neurons depolarized by 5 mV to cause 3.7-fold acceleration of spiking that was less synchronized with LFP. Both agents: evoked ‘post-agonist depression’ of LFP that correlated with the amplitude and kinetics of Vm hyperpolarization. The findings show that accelerated spiking during NMDA and glutamate is associated with enhanced or attenuated LC synchrony, respectively, causing distinct LFP pattern transformations. Shaping of LC population discharge dynamics by ionotropic glutamate receptors potentially fine-tunes its influence on brain functions.
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Waselenchuk Q, Ballanyi K. Autocrine Neuromodulation and Network Activity Patterns in the Locus Coeruleus of Newborn Rat Slices. Brain Sci 2022; 12:brainsci12040437. [PMID: 35447969 PMCID: PMC9024645 DOI: 10.3390/brainsci12040437] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/16/2022] [Accepted: 03/19/2022] [Indexed: 02/06/2023] Open
Abstract
Already in newborns, the locus coeruleus (LC) controls multiple brain functions and may have a complex organization as in adults. Our findings in newborn rat brain slices indicate that LC neurons (i) generate at ~1 Hz a ~0.3 s-lasting local field potential (LFP) comprising summated phase-locked single spike discharge, (ii) express intrinsic ‘pacemaker’ or ‘burster’ properties and (iii) receive solely excitatory or initially excitatory−secondary inhibitory inputs. μ-opioid or ɑ2 noradrenaline receptor agonists block LFP rhythm at 100−250 nM whereas slightly lower doses transform its bell-shaped pattern into slower crescendo-shaped multipeak bursts. GABAA and glycine receptors hyperpolarize LC neurons to abolish rhythm which remains though unaffected by blocking them. Rhythm persists also during ionotropic glutamate receptor (iGluR) inhibition whereas <10 mV depolarization during iGluR agonists accelerates spiking to cause subtype-specific fast (spindle-shaped) LFP oscillations. Similar modest neuronal depolarization causing a cytosolic Ca2+ rise occurs (without effect on neighboring astrocytes) during LFP acceleration by CNQX activating a TARP-AMPA-type iGluR complex. In contrast, noradrenaline lowers neuronal Ca2+ baseline via ɑ2 receptors, but evokes an ɑ1 receptor-mediated ‘concentric’ astrocytic Ca2+ wave. In summary, the neonatal LC has a complex (possibly modular) organization to enable discharge pattern transformations that might facilitate discrete actions on target circuits.
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Lee LHN, Huang CS, Chuang HH, Lai HJ, Yang CK, Yang YC, Kuo CC. An electrophysiological perspective on Parkinson's disease: symptomatic pathogenesis and therapeutic approaches. J Biomed Sci 2021; 28:85. [PMID: 34886870 PMCID: PMC8656091 DOI: 10.1186/s12929-021-00781-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/29/2021] [Indexed: 12/16/2022] Open
Abstract
Parkinson's disease (PD), or paralysis agitans, is a common neurodegenerative disease characterized by dopaminergic deprivation in the basal ganglia because of neuronal loss in the substantia nigra pars compacta. Clinically, PD apparently involves both hypokinetic (e.g. akinetic rigidity) and hyperkinetic (e.g. tremor/propulsion) symptoms. The symptomatic pathogenesis, however, has remained elusive. The recent success of deep brain stimulation (DBS) therapy applied to the subthalamic nucleus (STN) or the globus pallidus pars internus indicates that there are essential electrophysiological abnormalities in PD. Consistently, dopamine-deprived STN shows excessive burst discharges. This proves to be a central pathophysiological element causally linked to the locomotor deficits in PD, as maneuvers (such as DBS of different polarities) decreasing and increasing STN burst discharges would decrease and increase the locomotor deficits, respectively. STN bursts are not so autonomous but show a "relay" feature, requiring glutamatergic synaptic inputs from the motor cortex (MC) to develop. In PD, there is an increase in overall MC activities and the corticosubthalamic input is enhanced and contributory to excessive burst discharges in STN. The increase in MC activities may be relevant to the enhanced beta power in local field potentials (LFP) as well as the deranged motor programming at the cortical level in PD. Moreover, MC could not only drive erroneous STN bursts, but also be driven by STN discharges at specific LFP frequencies (~ 4 to 6 Hz) to produce coherent tremulous muscle contractions. In essence, PD may be viewed as a disorder with deranged rhythms in the cortico-subcortical re-entrant loops, manifestly including STN, the major component of the oscillating core, and MC, the origin of the final common descending motor pathways. The configurations of the deranged rhythms may play a determinant role in the symptomatic pathogenesis of PD, and provide insight into the mechanism underlying normal motor control. Therapeutic brain stimulation for PD and relevant disorders should be adaptively exercised with in-depth pathophysiological considerations for each individual patient, and aim at a final normalization of cortical discharge patterns for the best ameliorating effect on the locomotor and even non-motor symptoms.
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Affiliation(s)
- Lan-Hsin Nancy Lee
- Department of Physiology, National Taiwan University College of Medicine, 1 Jen-Ai Road, 1st Section, Taipei, 100, Taiwan.,Department of Neurology, Fu Jen Catholic University Hospital, New Taipei, Taiwan.,Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
| | - Chen-Syuan Huang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Hsiang-Hao Chuang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Hsing-Jung Lai
- Department of Physiology, National Taiwan University College of Medicine, 1 Jen-Ai Road, 1st Section, Taipei, 100, Taiwan.,Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.,National Taiwan University Hospital, Jin-Shan Branch, New Taipei, Taiwan
| | - Cheng-Kai Yang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Taoyuan, 333, Taiwan
| | - Ya-Chin Yang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan. .,Department of Biomedical Sciences, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Taoyuan, 333, Taiwan. .,Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Taoyuan, Taiwan.
| | - Chung-Chin Kuo
- Department of Physiology, National Taiwan University College of Medicine, 1 Jen-Ai Road, 1st Section, Taipei, 100, Taiwan. .,Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan.
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Li K, Abbott SBG, Shi Y, Eggan P, Gonye EC, Bayliss DA. TRPM4 mediates a subthreshold membrane potential oscillation in respiratory chemoreceptor neurons that drives pacemaker firing and breathing. Cell Rep 2021; 34:108714. [PMID: 33535052 PMCID: PMC7888550 DOI: 10.1016/j.celrep.2021.108714] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 12/04/2020] [Accepted: 01/12/2021] [Indexed: 12/01/2022] Open
Abstract
Brainstem networks that control regular tidal breathing depend on excitatory drive, including from tonically active, CO2/H+-sensitive neurons of the retrotrapezoid nucleus (RTN). Here, we examine intrinsic ionic mechanisms underlying the metronomic firing activity characteristic of RTN neurons. In mouse brainstem slices, large-amplitude membrane potential oscillations are evident in synaptically isolated RTN neurons after blocking action potentials. The voltage-dependent oscillations are abolished by sodium replacement; blocking calcium channels (primarily L-type); chelating intracellular Ca2+; and inhibiting TRPM4, a Ca2+-dependent cationic channel. Likewise, oscillation voltage waveform currents are sensitive to calcium and TRPM4 channel blockers. Extracellular acidification and serotonin (5-HT) evoke membrane depolarization that augments TRPM4-dependent oscillatory activity and action potential discharge. Finally, inhibition of TRPM4 channels in the RTN of anesthetized mice reduces central respiratory output. These data implicate TRPM4 in a subthreshold oscillation that supports the pacemaker-like firing of RTN neurons required for basal, CO2-stimulated, and state-dependent breathing.
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Affiliation(s)
- Keyong Li
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Stephen B G Abbott
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Yingtang Shi
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Pierce Eggan
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Elizabeth C Gonye
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA
| | - Douglas A Bayliss
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA.
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Different Activation Mechanisms of Excitatory Networks in the Rat Oculomotor Integrators for Vertical and Horizontal Gaze Holding. eNeuro 2020; 7:ENEURO.0364-19.2019. [PMID: 31852758 PMCID: PMC6975485 DOI: 10.1523/eneuro.0364-19.2019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 12/09/2019] [Accepted: 12/09/2019] [Indexed: 11/21/2022] Open
Abstract
Gaze holding in the horizontal and vertical directions is separately controlled via the oculomotor neural integrators, the prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC), respectively. Our previous in vitro studies demonstrated that transient, high-frequency local stimulation of the PHN and the INC increased the frequency of spontaneous EPSCs that lasted for several seconds. The sustained EPSC response of PHN neurons was attributed to the activation of local excitatory networks primarily mediated via Ca2+-permeable AMPA (CP-AMPA) receptors and Ca2+-activated nonselective cation (CAN) channels. However, the contribution of CP-AMPA receptors to the activation of INC excitatory networks appeared to be small. In this study, we clarified the mechanisms of excitatory network activation in the PHN and INC using whole-cell recordings in rat brainstem slices. Although physiological and histological analyses showed that neurons that expressed CP-AMPA receptors existed not only in the PHN but also in the INC, the effect of a CP-AMPA receptor antagonist on the sustained EPSC response was significantly weaker in INC neurons than in PHN neurons. Meanwhile, the effect of an NMDA receptor antagonist on the sustained EPSC response was significantly stronger in INC neurons than in PHN neurons. Furthermore, the current and the charge transfer mediated via NMDA receptors were significantly larger in INC neurons than in PHN neurons. These results strongly suggest that these excitatory networks are activated via different synaptic mechanisms: a CP-AMPA receptor and CAN channel-dependent mechanism and an NMDA receptor-dependent mechanism in horizontal and vertical integrators, respectively.
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Multistable properties of human subthalamic nucleus neurons in Parkinson's disease. Proc Natl Acad Sci U S A 2019; 116:24326-24333. [PMID: 31712414 PMCID: PMC6883794 DOI: 10.1073/pnas.1912128116] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Behaviors are realized through concerted activity in neural circuits. This activity results from a combination of neural connectivity and the properties of the involved neurons. By studying the activity of neurons in the human subthalamic nucleus during surgery for Parkinson’s disease, we report that these neurons have multiple stable states, and that brief electrical stimuli can lead to transitions between states. We thus suggest that these neurons function as finite state machines. The different states could influence the function of key motor circuits of the basal ganglia, and thus knowledge of these states in disease or in response to treatment could help to define new treatment strategies for people with movement disorders. To understand the function and dysfunction of neural circuits, it is necessary to understand the properties of the neurons participating in the behavior, the connectivity between these neurons, and the neuromodulatory status of the circuits at the time they are producing the behavior. Such knowledge of human neural circuits is difficult, at best, to obtain. Here, we study firing properties of human subthalamic neurons, using microelectrode recordings and microstimulation during awake surgery for Parkinson’s disease. We demonstrate that low-amplitude, brief trains of microstimulation can lead to persistent changes in neuronal firing behavior including switching between firing rates, entering silent periods, or firing several bursts then entering a silent period. We suggest that these multistable states reflect properties of finite state machines and could have implications for the function of circuits involving the subthalamic nucleus. Furthermore, understanding these states could lead to therapeutic strategies aimed at regulating the transitions between states.
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Ketamine blocks bursting in the lateral habenula to rapidly relieve depression. Nature 2018; 554:317-322. [PMID: 29446381 DOI: 10.1038/nature25509] [Citation(s) in RCA: 566] [Impact Index Per Article: 94.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 01/09/2018] [Indexed: 12/11/2022]
Abstract
The N-methyl-d-aspartate receptor (NMDAR) antagonist ketamine has attracted enormous interest in mental health research owing to its rapid antidepressant actions, but its mechanism of action has remained elusive. Here we show that blockade of NMDAR-dependent bursting activity in the 'anti-reward center', the lateral habenula (LHb), mediates the rapid antidepressant actions of ketamine in rat and mouse models of depression. LHb neurons show a significant increase in burst activity and theta-band synchronization in depressive-like animals, which is reversed by ketamine. Burst-evoking photostimulation of LHb drives behavioural despair and anhedonia. Pharmacology and modelling experiments reveal that LHb bursting requires both NMDARs and low-voltage-sensitive T-type calcium channels (T-VSCCs). Furthermore, local blockade of NMDAR or T-VSCCs in the LHb is sufficient to induce rapid antidepressant effects. Our results suggest a simple model whereby ketamine quickly elevates mood by blocking NMDAR-dependent bursting activity of LHb neurons to disinhibit downstream monoaminergic reward centres, and provide a framework for developing new rapid-acting antidepressants.
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Premotor Neuron Divergence Reflects Vocal Evolution. J Neurosci 2018; 38:5325-5337. [PMID: 29875228 DOI: 10.1523/jneurosci.0089-18.2018] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 04/09/2018] [Accepted: 04/28/2018] [Indexed: 11/21/2022] Open
Abstract
To identify mechanisms of behavioral evolution, we investigated the hindbrain circuit that generates distinct vocal patterns in two closely related frog species. Male Xenopus laevis and Xenopus petersii produce courtship calls that include a fast trill: trains of ∼60 Hz sound pulses. Although fast trill rates are similar, X. laevis fast trills have a longer duration and period than those of X. petersii To pinpoint the neural basis of these differences, we used whole-cell patch-clamp recordings in a key premotor hindbrain nucleus (the Xenopus parabrachial area, PBX) in ex vivo brains that produce fictive vocalizations, vocal nerve activity corresponding to advertisement call patterns. We found two populations of PBX neurons with distinct properties: fast trill neurons (FTNs) and early vocal neurons (EVNs). FTNs, but not EVNs, appear to be intrinsically tuned to produce each species' call patterns because: (1) X. laevis FTNs generate longer and slower depolarizations than X. petersii FTNs during their respective fictive vocalizations, (2) current steps in FTNs induce burst durations that are significantly longer in X. laevis than X. petersii, and (3) synaptically isolated FTNs oscillate in response to NMDA in a species-specific manner: longer and slower in X. laevis than in X. petersii Therefore, divergence of premotor neuron membrane properties is a strong candidate for generating vocal differences between species.SIGNIFICANCE STATEMENT The vertebrate hindbrain includes multiple neural circuits that generate rhythmic behaviors including vocalizations. Male African clawed frogs produce courtship calls that are unique to each species and differ in temporal patterns. Here, we identified two functional subtypes of neurons located in the parabrachial nucleus: a hindbrain region implicated in vocal and respiratory control across vertebrates. One of these neuronal subtypes exhibits distinct properties across species that can account for the evolutionary divergence of song patterns. Our results suggest that changes to this group of neurons during evolution may have had a major role in establishing novel behaviors in closely related species.
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Jaffe DB, Brenner R. A computational model for how the fast afterhyperpolarization paradoxically increases gain in regularly firing neurons. J Neurophysiol 2018; 119:1506-1520. [PMID: 29357445 DOI: 10.1152/jn.00385.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The gain of a neuron, the number and frequency of action potentials triggered in response to a given amount of depolarizing injection, is an important behavior underlying a neuron's function. Variations in action potential waveform can influence neuronal discharges by the differential activation of voltage- and ion-gated channels long after the end of a spike. One component of the action potential waveform, the afterhyperpolarization (AHP), is generally considered an inhibitory mechanism for limiting firing rates. In dentate gyrus granule cells (DGCs) expressing fast-gated BK channels, large fast AHPs (fAHP) are paradoxically associated with increased gain. In this article, we describe a mechanism for this behavior using a computational model. Hyperpolarization provided by the fAHP enhances activation of a dendritic inward current (a T-type Ca2+ channel is suggested) that, in turn, boosts rebound depolarization at the soma. The model suggests that the fAHP may both reduce Ca2+ channel inactivation and, counterintuitively, enhance its activation. The magnitude of the rebound depolarization, in turn, determines the activation of a subsequent, slower inward current (a persistent Na+ current is suggested) limiting the interspike interval. Simulations also show that the effect of AHP on gain is also effective for physiologically relevant stimulation; varying AHP amplitude affects interspike interval across a range of "noisy" stimulus frequency and amplitudes. The mechanism proposed suggests that small fAHPs in DGCs may contribute to their limited excitability. NEW & NOTEWORTHY The afterhyperpolarization (AHP) is canonically viewed as a major factor underlying the refractory period, serving to limit neuronal firing rate. We recently reported that enhancing the amplitude of the fast AHP (fAHP) in a relatively slowly firing neuron (vs. fast spiking neurons) expressing fast-gated BK channels augments neuronal excitability. In this computational study, we present a novel, quantitative hypothesis for how varying the amplitude of the fAHP can, paradoxically, influence a subsequent spike tens of milliseconds later.
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Affiliation(s)
- David B Jaffe
- Department of Biology, UTSA Neurosciences Institute, University of Texas at San Antonio , San Antonio, Texas
| | - Robert Brenner
- Department of Cell and Integrative Physiology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
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Rubin JE. Computational models of basal ganglia dysfunction: the dynamics is in the details. Curr Opin Neurobiol 2017; 46:127-135. [PMID: 28888856 DOI: 10.1016/j.conb.2017.08.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 08/22/2017] [Indexed: 12/18/2022]
Abstract
The development, simulation, and analysis of mathematical models offer helpful tools for integrating experimental findings and exploring or suggesting possible explanatory mechanisms. As models relating to basal ganglia dysfunction have proliferated, however, there has not always been consistency among their findings. This work points out several ways in which biological details, relating to ionic currents and synaptic pathways, can influence the dynamics of models of the basal ganglia under parkinsonian conditions and hence may be important for inclusion in models. It also suggests some additional useful directions for future modeling studies relating to basal ganglia dysfunction.
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Affiliation(s)
- Jonathan E Rubin
- Department of Mathematics and Center for the Neural Basis of Cognition, University of Pittsburgh, 301 Thackeray Hall, Pittsburgh, PA 15260, USA.
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11
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Girardi-Schappo M, Bortolotto GS, Stenzinger RV, Gonsalves JJ, Tragtenberg MHR. Phase diagrams and dynamics of a computationally efficient map-based neuron model. PLoS One 2017; 12:e0174621. [PMID: 28358843 PMCID: PMC5373601 DOI: 10.1371/journal.pone.0174621] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/12/2017] [Indexed: 11/18/2022] Open
Abstract
We introduce a new map-based neuron model derived from the dynamical perceptron family that has the best compromise between computational efficiency, analytical tractability, reduced parameter space and many dynamical behaviors. We calculate bifurcation and phase diagrams analytically and computationally that underpins a rich repertoire of autonomous and excitable dynamical behaviors. We report the existence of a new regime of cardiac spikes corresponding to nonchaotic aperiodic behavior. We compare the features of our model to standard neuron models currently available in the literature.
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Affiliation(s)
- Mauricio Girardi-Schappo
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, McGill University, Montreal Neurological Institute and Hospital, H3A 2B4, Montreal, Quebec, Canada
| | - Germano S. Bortolotto
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Rafael V. Stenzinger
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Jheniffer J. Gonsalves
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil
| | - Marcelo H. R. Tragtenberg
- Departamento de Física, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil
- * E-mail:
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Swanger SA, Vance KM, Pare JF, Sotty F, Fog K, Smith Y, Traynelis SF. NMDA Receptors Containing the GluN2D Subunit Control Neuronal Function in the Subthalamic Nucleus. J Neurosci 2015; 35:15971-83. [PMID: 26631477 PMCID: PMC4666920 DOI: 10.1523/jneurosci.1702-15.2015] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 10/20/2015] [Accepted: 10/29/2015] [Indexed: 01/25/2023] Open
Abstract
The GluN2D subunit of the NMDA receptor is prominently expressed in the basal ganglia and associated brainstem nuclei, including the subthalamic nucleus (STN), globus pallidus, striatum, and substantia nigra. However, little is known about how GluN2D-containing NMDA receptors contribute to synaptic activity in these regions. Using Western blotting of STN tissue punches, we demonstrated that GluN2D is expressed in the rat STN throughout development [age postnatal day 7 (P7)-P60] and in the adult (age P120). Immunoelectron microscopy of the adult rat brain showed that GluN2D is predominantly expressed in dendrites, unmyelinated axons, and axon terminals within the STN. Using subunit-selective allosteric modulators of NMDA receptors (TCN-201, ifenprodil, CIQ, and DQP-1105), we provide evidence that receptors containing the GluN2B and GluN2D subunits mediate responses to exogenously applied NMDA and glycine, as well as synaptic NMDA receptor activation in the STN of rat brain slices. EPSCs in the STN were mediated primarily by AMPA and NMDA receptors and GluN2D-containing NMDA receptors controlled the slow deactivation time course of EPSCs in the STN. In vivo recordings from the STN of anesthetized adult rats demonstrated that the spike firing rate was increased by the GluN2C/D potentiator CIQ and decreased by the GluN2C/D antagonist DQP-1105, suggesting that NMDA receptor activity can influence STN output. These data indicate that the GluN2B and GluN2D NMDA receptor subunits contribute to synaptic activity in the STN and may represent potential therapeutic targets for modulating subthalamic neuron activity in neurological disorders such as Parkinson's disease.
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Affiliation(s)
| | | | - Jean-François Pare
- Yerkes National Primate Research Center and Morris K. Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, Georgia 30329, and
| | - Florence Sotty
- H. Lundbeck A/S, Division of Neurodegeneration and Biologics, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Karina Fog
- H. Lundbeck A/S, Division of Neurodegeneration and Biologics, Ottiliavej 9, DK-2500 Valby, Denmark
| | - Yoland Smith
- Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322, Yerkes National Primate Research Center and Morris K. Udall Center of Excellence for Parkinson's Disease Research, Emory University, Atlanta, Georgia 30329, and
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AMP kinase regulates K-ATP currents evoked by NMDA receptor stimulation in rat subthalamic nucleus neurons. Neuroscience 2014; 274:138-52. [PMID: 24875176 DOI: 10.1016/j.neuroscience.2014.05.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/10/2014] [Accepted: 05/18/2014] [Indexed: 11/21/2022]
Abstract
Our lab recently showed that N-methyl-D-aspartate (NMDA) evokes ATP-sensitive K(+) (K-ATP) currents in subthalamic nucleus (STN) neurons in slices of the rat brain. Both K-ATP channels and 5'-adenosine monophosphate-activated protein kinase (AMPK) are considered cellular energy sensors because their activities are influenced by the phosphorylation state of adenosine nucleotides. Moreover, AMPK has been shown to regulate K-ATP function in a variety of tissues including pancreas, cardiac myocytes, and hypothalamus. We used whole-cell patch clamp recordings to study the effect of AMPK activation on K-ATP channel function in STN neurons in slices of the rat brain. We found that bath or intracellular application of the AMPK activators A769662 and PT1 augmented tolbutamide-sensitive K-ATP currents evoked by NMDA receptor stimulation. The effect of AMPK activators was blocked by the AMPK inhibitor dorsomorphin (compound C), and by STO609, an inhibitor of the upstream AMPK activator CaMKKβ. AMPK augmentation of NMDA-induced K-ATP current was also blocked by intracellular BAPTA and by inhibitors of nitric oxide synthase and guanylyl cyclase. However, A769662 did not augment currents evoked by the K-ATP channel opener diazoxide. In the presence of NMDA, A769662 inhibited depolarizing plateau potentials and burst firing, both of which could be antagonized by tolbutamide or dorsomorphin. These studies show that AMPK augments NMDA-induced K-ATP currents by a Ca(2+)-dependent process that involves nitric oxide and cGMP. By augmenting K-ATP currents, AMPK activation would be expected to dampen the excitatory effect of glutamate-mediated transmission in the STN.
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Abstract
The development and the ionic nature of bistable behavior in lumbar motoneurons were investigated in rats. One week after birth, almost all (∼80%) ankle extensor motoneurons recorded in whole-cell configuration displayed self-sustained spiking in response to a brief depolarization that emerged when the temperature was raised >30°C. The effect of L-type Ca(2+) channel blockers on self-sustained spiking was variable, whereas blockade of the persistent sodium current (I(NaP)) abolished them. When hyperpolarized, bistable motoneurons displayed a characteristic slow afterdepolarization (sADP). The sADPs generated by repeated depolarizing pulses summed to promote a plateau potential. The sADP was tightly associated with the emergence of Ca(2+) spikes. Substitution of extracellular Na(+) or chelation of intracellular Ca(2+) abolished both sADP and the plateau potential without affecting Ca(2+) spikes. These data suggest a key role of a Ca(2+)-activated nonselective cation conductance ((CaN)) in generating the plateau potential. In line with this, the blockade of (CaN) by flufenamate abolished both sADP and plateau potentials. Furthermore, 2-aminoethoxydiphenyl borate (2-APB), a common activator of thermo-sensitive vanilloid transient receptor potential (TRPV) cation channels, promoted the sADP. Among TRPV channels, only the selective activation of TRPV2 channels by probenecid promoted the sADP to generate a plateau potential. To conclude, bistable behaviors are, to a large extent, determined by the interplay between three currents: L-type I(Ca), I(NaP), and a Na(+)-mediated I(CaN) flowing through putative TRPV2 channels.
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TRPM2 channels are required for NMDA-induced burst firing and contribute to H(2)O(2)-dependent modulation in substantia nigra pars reticulata GABAergic neurons. J Neurosci 2013; 33:1157-68. [PMID: 23325252 DOI: 10.1523/jneurosci.2832-12.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Substantia nigra pars reticulata (SNr) GABAergic neurons are projection neurons that convey output from the basal ganglia to target structures. These neurons exhibit spontaneous regular firing, but also exhibit burst firing in the presence of NMDA or when excitatory glutamatergic input to the SNr is activated. Notably, an increase in burst firing is also seen in Parkinson's disease. Therefore, elucidating conductances that mediate spontaneous activity and changes of firing pattern in these neurons is essential for understanding how the basal ganglia control movement. Using ex vivo slices of guinea pig midbrain, we show that SNr GABAergic neurons express transient receptor potential melastatin 2 (TRPM2) channels that underlie NMDA-induced burst firing. Furthermore, we show that spontaneous firing rate and burst activity are modulated by the reactive oxygen species H(2)O(2) acting via TRPM2 channels. Thus, our results indicate that activation of TRPM2 channels is necessary for burst firing in SNr GABAergic neurons and their responsiveness to modulatory H(2)O(2). These findings have implications not only for normal regulation, but also for Parkinson's disease, which involves excitotoxicity and oxidative stress.
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16
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Grant PF, Lowery MM. Simulation of cortico-basal ganglia oscillations and their suppression by closed loop deep brain stimulation. IEEE Trans Neural Syst Rehabil Eng 2012; 21:584-94. [PMID: 22695362 DOI: 10.1109/tnsre.2012.2202403] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A new model of deep brain stimulation (DBS) is presented that integrates volume conduction effects with a neural model of pathological beta-band oscillations in the cortico-basal ganglia network. The model is used to test the clinical hypothesis that closed-loop control of the amplitude of DBS may be possible, based on the average rectified value of beta-band oscillations in the local field potential. Simulation of closed-loop high-frequency DBS was shown to yield energy savings, with the magnitude of the energy saved dependent on the strength of coupling between the subthalamic nucleus and the remainder of the cortico-basal ganglia network. When closed-loop DBS was applied to a strongly coupled cortico-basal ganglia network, the stimulation energy delivered over a 480 s period was reduced by up to 42%. Greater energy reductions were observed for weakly coupled networks, as the stimulation amplitude reduced to zero once the initial desynchronization had occurred. The results provide support for the application of closed-loop high-frequency DBS based on electrophysiological biomarkers.
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Affiliation(s)
- Peadar F Grant
- School of Electrical, Electronic and Communications Engineering, University College Dublin, Dublin, Ireland.
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17
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Chu JU, Jeong MJ, Song KI, Lee HC, Kim J, Kim YJ, Choi K, Suh JKF, Youn I. Spontaneous synchronized burst firing of subthalamic nucleus neurons in rat brain slices measured on multi-electrode arrays. Neurosci Res 2012; 72:324-40. [PMID: 22306063 DOI: 10.1016/j.neures.2012.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 01/16/2012] [Accepted: 01/16/2012] [Indexed: 11/25/2022]
Abstract
The current study presents an organotypic rat midbrain slice culture that served as a consistent and informative framework, where the STN neurons and their interconnectivity were closely examined with respect to electrophysiological and pharmacological properties. From multi-electrode array recordings, it was found that the majority of STN neurons spontaneously fired in bursts rather than tonically under control conditions, and the neural activity between pairs of burst-firing STN neurons was tightly correlated. This spontaneous synchronized burst firing was also affected by a glutamate receptor antagonist, yet unaffected by a GABA receptor antagonist. Moreover, even when the STN was isolated from all its known external inputs, spontaneous synchronized burst firing was still observed under control conditions and consistently switched to tonic firing following the application of a glutamate receptor antagonist. Therefore, the results indicated the existence of glutamatergic projections to the STN in the slice preparation, and these excitatory synaptic connections appeared to originate from axon collaterals within the STN rather than other basal ganglia nuclei. It could be concluded that the STN neurons and their interconnectivity are essential requirements in the rat brain slice preparation to produce spontaneous synchronized burst firing.
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Affiliation(s)
- Jun-Uk Chu
- Biomedical Research Institute, Korea Institute of Science and Technology, 39-1 Hawolgok-dong, Seongbuk-gu, Seoul 136-791, Republic of Korea
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18
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The Ca2+-Activated Monovalent Cation-Selective Channels TRPM4 and TRPM5. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2012. [DOI: 10.1007/978-1-62703-077-9_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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19
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Intrinsic dynamics and synaptic inputs control the activity patterns of subthalamic nucleus neurons in health and in Parkinson's disease. Neuroscience 2011; 198:54-68. [PMID: 21723918 DOI: 10.1016/j.neuroscience.2011.06.049] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/10/2011] [Accepted: 06/15/2011] [Indexed: 11/22/2022]
Abstract
Neurons in the subthalamic nucleus occupy a pivotal position in the circuitry of the basal ganglia. They receive direct excitatory input from the cerebral cortex and the intralaminar nuclei of the thalamus, and directly excite the inhibitory basal ganglia output neurons in the internal segment of the globus pallidus and the substantia nigra. They are also engaged in a reciprocal synaptic arrangement with inhibitory neurons in the external segment of the globus pallidus. Although once viewed as a simple relay of extrinsic input to the basal ganglia, physiological studies of subthalamic neurons have revealed that activity in these neurons does not directly reflect their pattern of extrinsic excitation. Subthalamic neurons are autonomously active at rates comparable to those observed in vivo, and they generate complex patterns of intrinsic activity arising from the interactions between voltage sensitive ion channels on the somatodendritic and axonal membranes. Extrinsic synaptic excitation does not create the firing pattern of the subthalamic neuron, but rather controls the timing of action potentials generated intrinsically. The dopaminergic innervation of the subthalamic nucleus, although moderate, can directly influence firing patterns by acting both on synaptic transmission and voltage-sensitive ion channels responsible for intrinsic properties. Furthermore, chronic dopamine depletion in Parkinson's disease may modify both synaptic transmission and integration in the subthalamic nucleus, in addition to its effects on other regions of the basal ganglia.
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20
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Ammari R, Bioulac B, Garcia L, Hammond C. The Subthalamic Nucleus becomes a Generator of Bursts in the Dopamine-Depleted State. Its High Frequency Stimulation Dramatically Weakens Transmission to the Globus Pallidus. Front Syst Neurosci 2011; 5:43. [PMID: 21716635 PMCID: PMC3115486 DOI: 10.3389/fnsys.2011.00043] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 06/01/2011] [Indexed: 11/29/2022] Open
Abstract
Excessive burst firing in the dopamine-depleted basal ganglia correlates with severe motor symptoms of Parkinson's disease that are attenuated by high frequency electrical stimulation of the subthalamic nucleus (STN). Here we test the hypothesis that pathological bursts in dopamine-deprived basal ganglia are generated within the STN and transmitted to globus pallidus neurons. To answer this question we recorded excitatory synaptic currents and potentials from subthalamic and pallidal neurons in the basal ganglia slice (BGS) from dopamine-depleted mice while continuously blocking GABAA receptors. In control mice, a single electrical stimulus delivered to the internal capsule or the rostral pole of the STN evoked a short duration, small amplitude, monosynaptic EPSC in subthalamic neurons. In contrast, in the dopamine-depleted BGS, this monosynaptic EPSC was amplified and followed by a burst of polysynaptic EPSCs that eventually reverberated three to seven times, providing a long lasting response that gave rise to bursts of EPSCs and spikes in GP neurons. Repetitive (10–120 Hz) stimulation delivered to the STN in the dopamine-depleted BGS attenuated STN-evoked bursts of EPSCs in pallidal neurons after several minutes of stimulation but only high frequency (90–120 Hz) stimulation replaced them with small amplitude EPSCs at 20 Hz. We propose that the polysynaptic pathway within the STN amplifies subthalamic responses to incoming excitation in the dopamine-depleted basal ganglia, thereby transforming the STN into a burst generator and entraining pallidal neurons in pathogenic bursting activities. High frequency stimulation of the STN prevents the transmission of this pathological activity to globus pallidus and imposes a new glutamatergic synaptic noise on pallidal neurons.
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21
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Kubota S, Rubin JE. NMDA-induced burst firing in a model subthalamic nucleus neuron. J Neurophysiol 2011; 106:527-37. [PMID: 21562199 DOI: 10.1152/jn.01127.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Experiments in rat brain slice show that hyperpolarized subthalamic nucleus (STN) neurons engage in slow, regular burst firing when treated with an N-methyl-d-aspartate (NMDA) bath. A depolarization-activated inward current (DIC) has been hypothesized to contribute to this bursting activity. To explore the mechanism for STN burst firing in this setting, we augmented a previously published conductance-based computational model for single rat STN neurons to include both DIC and NMDA currents, fit to data from published electrophysiological recordings. Simulations show that with these additions, the model engages in bursting activity at <1 Hz in response to hyperpolarizing current injection and that this bursting exhibits several features observed experimentally in STN. Furthermore, a reduced model is used to show that the combination of NMDA and DIC currents, but not either alone, suffices to generate oscillations under hyperpolarizing current injection. STN neurons show enhanced burstiness in Parkinson's disease patients and experimental models of parkinsonism, and the burst mechanism studied presently could contribute to this effect.
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Affiliation(s)
- Shigeru Kubota
- Graduate School of Science and Engineering, Yamagata University, Yonezawa, Yamagata, Japan
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22
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Mrejeru A, Wei A, Ramirez JM. Calcium-activated non-selective cation currents are involved in generation of tonic and bursting activity in dopamine neurons of the substantia nigra pars compacta. J Physiol 2011; 589:2497-514. [PMID: 21486760 DOI: 10.1113/jphysiol.2011.206631] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Nigral dopamine neurons are transiently activated by high frequency glutamatergic inputs relaying reward-predicting sensory information. The tonic firing pattern of dopamine cells responds to these inputs with a transient burst of spikes that requires NMDA receptors. Here, we show that NMDA receptor activation further excites the cell by recruiting a calcium-activated non-selective cation current (ICAN) capable of generating a plateau potential. Burst firing in vitro is eliminated after blockade of ICAN with flufenamic acid, 9-phenanthrol, or intracellular BAPTA. ICAN is likely to be mediated by a transient receptor potential (TRP) channel, and RT-PCR was used to confirm expression of TRPM2 and TRPM4mRNA in substantia nigra pars compacta.We propose that ICAN is selectively activated during burst firing to boost NMDA currents and allow plateau potentials. This boost mechanism may render DA cells vulnerable to excitotoxicity.
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Affiliation(s)
- Ana Mrejeru
- Committee on Neurobiology, University of Chicago, Chicago, IL 60637, USA
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23
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Synaptic mechanism for the sustained activation of oculomotor integrator circuits in the rat prepositus hypoglossi nucleus: contribution of Ca2+-permeable AMPA receptors. J Neurosci 2010; 30:15735-46. [PMID: 21106813 DOI: 10.1523/jneurosci.2814-10.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Sustained neural activity is involved in several brain functions. Although recurrent/feedback excitatory networks are proposed as a neural mechanism for this sustained activity, the synaptic mechanisms have not been fully clarified. To address this issue, we investigated the excitatory synaptic responses of neurons in the prepositus hypoglossi nucleus (PHN), a brainstem structure involved as an oculomotor neural integrator, using whole-cell voltage-clamp recordings in rat slice preparations. Under a blockade of inhibitory synaptic transmissions, the application of "burst stimulation" (100 Hz, 20 pulses) to a brainstem area projecting to the PHN induced an increase in the frequency of EPSCs in PHN neurons that lasted for several seconds. Sustained EPSC responses were observed even when the burst stimulation was applied in the vicinity of a recorded neuron within the PHN that was isolated from the slices. Pharmacologically, the sustained EPSC responses were reduced by 1-naphthyl acetyl spermine (50 μm), a blocker of Ca(2+)-permeable AMPA (CP-AMPA) receptors. Analysis of the current-voltage (I-V) relationship of the current responses to iontophoretic application of kainate revealed that more than one-half of PHN neurons exhibited an inwardly rectifying I-V relationship. Furthermore, PHN neurons exhibiting inwardly rectifying current responses showed higher Ca(2+) permeability. The sustained EPSC responses were also reduced by flufenamic acid (200 μm), a blocker of Ca(2+)-activated nonselective cation (CAN) channels. These results indicate that the sustained EPSC responses are attributable to the sustained activation of local excitatory networks in the PHN, which arises from the activation of CP-AMPA receptors and CAN channels in PHN neurons.
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24
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Pissadaki EK, Sidiropoulou K, Reczko M, Poirazi P. Encoding of spatio-temporal input characteristics by a CA1 pyramidal neuron model. PLoS Comput Biol 2010; 6:e1001038. [PMID: 21187899 PMCID: PMC3002985 DOI: 10.1371/journal.pcbi.1001038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 11/19/2010] [Indexed: 11/26/2022] Open
Abstract
The in vivo activity of CA1 pyramidal neurons alternates between regular spiking and bursting, but how these changes affect information processing remains unclear. Using a detailed CA1 pyramidal neuron model, we investigate how timing and spatial arrangement variations in synaptic inputs to the distal and proximal dendritic layers influence the information content of model responses. We find that the temporal delay between activation of the two layers acts as a switch between excitability modes: short delays induce bursting while long delays decrease firing. For long delays, the average firing frequency of the model response discriminates spatially clustered from diffused inputs to the distal dendritic tree. For short delays, the onset latency and inter-spike-interval succession of model responses can accurately classify input signals as temporally close or distant and spatially clustered or diffused across different stimulation protocols. These findings suggest that a CA1 pyramidal neuron may be capable of encoding and transmitting presynaptic spatiotemporal information about the activity of the entorhinal cortex-hippocampal network to higher brain regions via the selective use of either a temporal or a rate code. Pyramidal neurons in the hippocampus are crucially involved in learning and memory functions, but the ways in which they contribute to the processing of sensory inputs and their internal representation remain mostly unclear. The principal neurons of the CA1 region of the hippocampus are surrounded by at least 21 different types of interneurons. This feature, together with the fact that CA1 pyramidal dendrites associate two major glutamatergic inputs arriving from the entorhinal cortex, makes it laborious to track the ‘how’ and ‘what’ of synaptic integration. The present study tries to shed light on the ‘what’, that is, the information content of the CA1 discharge pattern. Using a detailed biophysical CA1 neuron model, we show that the output of the model neuron contains spatial and temporal features of the incoming synaptic input. This information lies in the temporal pattern of the inter-spike intervals produced during the bursting activity which is induced by the temporal coincidence of the two activated synaptic streams. Our findings suggest that CA1 pyramidal neurons may be capable of capturing features of the ongoing network activity via the use of a temporal code for information transfer.
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Affiliation(s)
- Eleftheria Kyriaki Pissadaki
- Department of Biology, University of Crete, Heraklion, Crete, Greece
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
- * E-mail: (EKP); (PP)
| | - Kyriaki Sidiropoulou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
| | - Martin Reczko
- Institute of Molecular Oncology, Alexander Fleming Biomedical Sciences Research Center, Athens, Greece
| | - Panayiota Poirazi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
- * E-mail: (EKP); (PP)
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25
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Ca2+ influx through NMDA-gated channels activates ATP-sensitive K+ currents through a nitric oxide-cGMP pathway in subthalamic neurons. J Neurosci 2010; 30:1882-93. [PMID: 20130197 DOI: 10.1523/jneurosci.3200-09.2010] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Excessive burst firing of action potentials in subthalamic nucleus (STN) neurons has been correlated with the bradykinesia and rigidity seen in Parkinson's disease. Consequently, there is much interest in characterizing mechanisms that promote burst firing, such as the regulation of NMDA receptor function. Using whole-cell recording techniques in rat brain slices, we report that inward currents evoked by NMDA are greatly potentiated by ATP-sensitive K(+) (K-ATP) channel blocking agents in STN neurons but not in dopamine neurons in the substantia nigra. Moreover, we found that the ability of NMDA to evoke K-ATP current was blocked by inhibitors of nitric oxide synthase, guanylyl cyclase, and calcium/calmodulin. By altering firing patterns of STN neurons, this NMDA/K-ATP interaction may exert an important influence on basal ganglia output and thereby affect the clinical expression of Parkinson's disease.
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26
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Bernier AP, Arsenault I, Lund JP, Kolta A. Effect of the Stimulation of Sensory Inputs on the Firing of Neurons of the Trigeminal Main Sensory Nucleus in the Rat. J Neurophysiol 2010; 103:915-23. [PMID: 19955291 DOI: 10.1152/jn.91109.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mastication can be triggered by repetitive stimulation of the cortex or of sensory inputs, but is patterned by a brain stem central pattern generator (CPG). This CPG may include the dorsal part of the principal trigeminal sensory nucleus (NVsnpr), where neurons burst repetitively when the extracellular concentration of Ca2+ ([Ca2+]e) drops. We examined the effects of repetitive stimulation of sensory afferents of the trigeminal tract on activity of NVsnpr neurons recorded extracellularly in vitro under physiologic [Ca2+]e (1.6 mM). Spontaneously active cells had either a tonic ( n = 145) or a bursting ( n = 46) firing pattern. Afferent stimulation altered burst duration and/or burst frequency in bursting cells and firing frequency in most tonic cells. In 28% of the latter, the firing pattern switched to rhythmic bursting. This effect could be mimicked by local application of N-methyl-d-aspartate and blocked by APV but not DNQX. Detailed analysis showed that rhythm indices (RIs) of 35 tonic neurons that were negative (nonrhythmic) before stimulation became significantly rhythmic (RI ≥ 0.01) after stimulation. Mean and median bursting frequency of these units were 8.32 ± 0.72 (SE) Hz and 6.25 Hz (range, 2.5–17.5 Hz). In seven instances, two units were recorded simultaneously, and cross-correlation analysis showed that firing of six pairs was rhythmic and synchronized after stimulation. Optimal stimulation parameters for eliciting rhythmic bursting consisted in 500-ms trains of pulses delivered at 40–60 Hz. Together, our results show that repetitive stimulation of sensory afferents in vitro can elicit masticatory-like rhythmic bursting in NVsnpr neurons at physiological [Ca2+]e.
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Affiliation(s)
- A. P. Bernier
- Groupe de Recherche sur le Système Nerveux Central du Fonds de la Recherche en Santé du Québec, Université de Montréal
| | - I. Arsenault
- Groupe de Recherche sur le Système Nerveux Central du Fonds de la Recherche en Santé du Québec, Université de Montréal
| | - J. P. Lund
- Groupe de Recherche sur le Système Nerveux Central du Fonds de la Recherche en Santé du Québec, Université de Montréal
- Faculty of Dentistry, McGill University; and
| | - A. Kolta
- Groupe de Recherche sur le Système Nerveux Central du Fonds de la Recherche en Santé du Québec, Université de Montréal
- Faculty of Dentistry, McGill University; and
- Faculté de Médecine Dentaire, Université de Montréal, Montreal, Quebec, Canada
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27
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Subthalamic nucleus evokes similar long lasting glutamatergic excitations in pallidal, entopeduncular and nigral neurons in the basal ganglia slice. Neuroscience 2010; 166:808-18. [PMID: 20074618 DOI: 10.1016/j.neuroscience.2010.01.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 01/06/2010] [Indexed: 11/20/2022]
Abstract
The subthalamic nucleus (STN) modulates the activity of globus pallidus (GP), entopeduncular nucleus (EP) and substantia nigra pars reticulata (SNr) neurons via its direct glutamatergic projections. To investigate the mechanism by which STN affects activity in these structures and whether STN induced activity is comparable among STN target neurons, we performed patch clamp recordings in a tilted, parasagittal, basal ganglia slice (BGS) that preserves these functional connections. We report that single, brief stimulation of the STN generates a brief monosynaptic AMPA-mediated excitatory postsynaptic current (EPSC) in GP, EP and SNr neurons. A higher intensity, supra-threshold activation evokes a compound EPSC consisting of an early monosynaptic component followed by a slow inward NMDA-mediated current with an overlying barrage of AMPA-mediated EPSCs. These late EPSCs were polysynaptic and gave rise to bursts of spikes that lasted several hundreds of milliseconds. They were eliminated by surgical removal of the STN from the BGS slice, indicating that the STN is required for their generation. Reconstruction of biocytin-filled STN neurons revealed that a third of STN neurons project intra-STN axon collaterals that may underlie polysynaptic activity. We propose that activation of the STN yields comparable long lasting excitations in its target neurons by means of a polysynaptic network.
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28
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Kolta A, Morquette P, Lavoie R, Arsenault I, Verdier D. Modulation of rhythmogenic properties of trigeminal neurons contributing to the masticatory CPG. BREATHE, WALK AND CHEW: THE NEURAL CHALLENGE: PART I 2010; 187:137-48. [DOI: 10.1016/b978-0-444-53613-6.00009-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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29
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Dong HW, Hayar A, Callaway J, Yang XH, Nai Q, Ennis M. Group I mGluR activation enhances Ca(2+)-dependent nonselective cation currents and rhythmic bursting in main olfactory bulb external tufted cells. J Neurosci 2009; 29:11943-53. [PMID: 19776280 PMCID: PMC3837548 DOI: 10.1523/jneurosci.0206-09.2009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 06/24/2009] [Accepted: 08/16/2009] [Indexed: 11/21/2022] Open
Abstract
In the main olfactory bulb, activation of group I metabotropic glutamate receptors (mGluRs) by olfactory nerve stimulation generates slow (2 Hz) oscillations near the basal respiratory frequency. These oscillations arise in the glomerular layer and may be generated, in part, by the intrinsic neurons, the juxtaglomerular neurons. We investigated the physiological effects of group I mGluR agonists on one population of juxtaglomerular neurons, external tufted (ET) cells, which rhythmically burst at respiratory frequencies and synchronize the intraglomerular network. Electrophysiological studies in rat main olfactory bulb slices demonstrated that the mGluR agonist 3,4-dihydroxyphenylglycine (DHPG) amplified the strength of ET cell spike bursts, principally by increasing the number of spikes per burst. Voltage-clamp and Ca(2+)-imaging studies showed that DHPG elicits a Ca(2+)-dependent nonselective cation current (I(CAN)) in the dendrites of ET cells triggered by Ca(2+) release from internal stores. The DHPG effects on bursting and membrane current were attenuated by flufenamic acid and SKF96365, agents known to antagonize I(CAN) in a variety of neurons. DHPG also elicited slow membrane current oscillations and spikelets in ET cells when synaptic transmission and intrinsic membrane channels were inoperative. These findings indicate that DHPG may passively (by increasing burst strength) or actively (by increasing conductance of gap junctions) enhance the strength of electrical synapses between ET cells. Together, these findings indicate that activation of group I mGluRs on the dendrites of ET cells play a key role in the generation of slow rhythmic oscillation in the glomerular network, which is in turn tuned to sniffing of the animal in vivo.
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Affiliation(s)
- Hong-Wei Dong
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, 38163, USA.
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30
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Calcium-activated nonspecific cation current and synaptic depression promote network-dependent burst oscillations. Proc Natl Acad Sci U S A 2009; 106:2939-44. [PMID: 19196976 DOI: 10.1073/pnas.0808776106] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Central pattern generators (CPGs) produce neural-motor rhythms that often depend on specialized cellular or synaptic properties such as pacemaker neurons or alternating phases of synaptic inhibition. Motivated by experimental evidence suggesting that activity in the mammalian respiratory CPG, the preBötzinger complex, does not require either of these components, we present and analyze a mathematical model demonstrating an unconventional mechanism of rhythm generation in which glutamatergic synapses and the short-term depression of excitatory transmission play key rhythmogenic roles. Recurrent synaptic excitation triggers postsynaptic Ca(2+)-activated nonspecific cation current (I(CAN)) to initiate a network-wide burst. Robust depolarization due to I(CAN) also causes voltage-dependent spike inactivation, which diminishes recurrent excitation and thus attenuates postsynaptic Ca(2+) accumulation. Consequently, activity-dependent outward currents-produced by Na/K ATPase pumps or other ionic mechanisms-can terminate the burst and cause a transient quiescent state in the network. The recovery of sporadic spiking activity rekindles excitatory interactions and initiates a new cycle. Because synaptic inputs gate postsynaptic burst-generating conductances, this rhythm-generating mechanism represents a new paradigm that can be dubbed a 'group pacemaker' in which the basic rhythmogenic unit encompasses a fully interdependent ensemble of synaptic and intrinsic components. This conceptual framework should be considered as an alternative to traditional models when analyzing CPGs for which mechanistic details have not yet been elucidated.
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31
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Carrillo-Reid L, Tecuapetla F, Ibáñez-Sandoval O, Hernández-Cruz A, Galarraga E, Bargas J. Activation of the Cholinergic System Endows Compositional Properties to Striatal Cell Assemblies. J Neurophysiol 2009; 101:737-49. [DOI: 10.1152/jn.90975.2008] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Striatal cell assemblies are thought to encode network states related to associative learning, procedural memory, and the sequential organization of behavior. Cholinergic neurotransmission modulates memory processes in the striatum and other brain structures. This work asks if the activity of striatal microcircuits observed in living nervous tissue, with attributes similar to cell assemblies, exhibit some of the properties proposed to be necessary to compose memory traces. Accordingly, we used whole cell and calcium-imaging techniques to investigate the cholinergic modulation of striatal neuron pools that have been reported to exhibit several properties expected from cell assemblies such as synchronous states of activity and the alternation of this activity among different neuron pools. We analyzed the cholinergic modulation of the activity of neuron pools with multidimensional reduction techniques and vectorization of network dynamics. It was found that the activation of the cholinergic system enables striatal cell assemblies with properties that have been posited for recurrent neural artificial networks with memory storage capabilities. Graph theory techniques applied to striatal network states revealed sequences of vectors with a recursive dynamics similar to closed reverberating cycles. The cycles exhibited a modular architecture and a hierarchical organization. It is then concluded that, under certain conditions, the cholinergic system enables the striatal microcircuit with the ability to compose complex sequences of activity. Neuronal recurrent networks with the characteristics encountered in the present experiments are proposed to allow repeated sequences of activity to become memories and repeated memories to compose learned motor procedures.
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32
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Depolarisation and suppression of burst firing activity in the mouse subthalamic nucleus by dopamine D1/D5 receptor activation of a cyclic-nucleotide gated non-specific cation conductance. Neuropharmacology 2008; 55:94-105. [DOI: 10.1016/j.neuropharm.2008.04.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 04/25/2008] [Accepted: 04/25/2008] [Indexed: 11/20/2022]
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Strauss U, Zhou FW, Henning J, Battefeld A, Wree A, Köhling R, Haas SJP, Benecke R, Rolfs A, Gimsa U. Increasing extracellular potassium results in subthalamic neuron activity resembling that seen in a 6-hydroxydopamine lesion. J Neurophysiol 2008; 99:2902-15. [PMID: 18385482 DOI: 10.1152/jn.00402.2007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Abnormal neuronal activity in the subthalamic nucleus (STN) plays a crucial role in the pathophysiology of Parkinson's disease (PD). Although altered extracellular potassium concentration ([K+]o) and sensitivity to [K+]o modulates neuronal activity, little is known about the potassium balance in the healthy and diseased STN. In vivo measurements of [K+]o using ion-selective electrodes demonstrated a twofold increase in the decay time constant of lesion-induced [K+]o transients in the STN of adult Wistar rats with a unilateral 6-hydroxydopamine (6-OHDA) median forebrain bundle lesion, employed as a model of PD, compared with nonlesioned rats. Various [K+]o concentrations (1.5-12.5 mM) were applied to in vitro slice preparations of three experimental groups of STN slices from nonlesioned control rats, ipsilateral hemispheres, and contralateral hemispheres of lesioned rats. The majority of STN neurons of nonlesioned rats and in slices contralateral to the lesion fired spontaneously, predominantly in a regular pattern, whereas those in slices ipsilateral to the lesion fired more irregularly or even in bursts. Experimentally increased [K+]o led to an increase in the number of spontaneously firing neurons and action potential firing rates in all groups. This was accompanied by a decrease in the amplitude of post spike afterhyperpolarization (AHP) and the amplitude and duration of the posttrain AHP. Lesion effects in ipsilateral neurons at physiological [K+]o resembled the effects of elevated [K+]o in nonlesioned rats. Our data suggest that changed potassium sensitivity due to conductivity alterations and delayed clearance may be critical for shaping STN activity in parkinsonian states.
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Affiliation(s)
- Ulf Strauss
- Neurobiology, Department of Neurology, University of Rostock, Rostock, Germany.
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Sharifullina E, Ostroumov K, Grandolfo M, Nistri A. N-methyl-D-aspartate triggers neonatal rat hypoglossal motoneurons in vitro to express rhythmic bursting with unusual Mg2+ sensitivity. Neuroscience 2008; 154:804-20. [PMID: 18468805 DOI: 10.1016/j.neuroscience.2008.03.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 02/05/2008] [Accepted: 03/04/2008] [Indexed: 10/22/2022]
Abstract
The brainstem nucleus hypoglossus innervates the tongue which must contract rhythmically during respiration, chewing and swallowing. Such rhythmic discharges are due to network bursting mediated by AMPA receptor-dependent glutamatergic transmission. The contribution by hypoglossal motoneurons themselves to rhythmicity remains, however, unclear as they might simply express cyclic patterns produced by premotoneurons or, in analogy to spinal motoneurons, might participate to bursting due to activation of their N-methyl-D-aspartate (NMDA) receptors. Using patch clamp recording from hypoglossal motoneurons in slice preparations of neonatal rat brainstem, we observed that NMDA directly depolarized motoneurons to generate various discharge patterns. Most motoneurons produced transient bursts which were consistently restored by repolarizing membrane potential to rest. Fewer motoneurons generated either sustained bursting or random firing. Rhythmic bursts were recorded from XII nerve rootlets even when single motoneuron bursting required hyperpolarization. NMDA evoked bursts were blocked by the Ca2+ antagonist Cd2+, the gap junction blocker carbenoxolone, or Mg2+ free solution, and partially inhibited by tetrodotoxin or nifedipine. Under voltage clamp, NMDA-induced bursting persisted at negative or positive potentials and was resistant to high extracellular Mg2+ in accordance with the observation of widespread motoneuron expression of NMDA 2D receptor subunits that confer poor Mg2+ sensitivity. It is proposed that NMDA depolarized motoneurons with the contribution of Mg2+ insensitive channels, and triggered bursting via cyclic activation/deactivation of voltage-dependent Na+, Ca2+ and K+ currents spread through gap junctions. The NMDA-evoked bursting pattern was similar to the rhythmic discharges previously recorded from the XII nerve during milk sucking by neonatal rats.
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Affiliation(s)
- E Sharifullina
- Neurobiology Sector, International School for Advanced Studies, Via Beirut 2-4, Trieste, Italy
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35
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Gillies A, Willshaw D. Neuroinformatics and modeling of the basal ganglia: bridging pharmacology and physiology. Expert Rev Med Devices 2007; 4:663-72. [PMID: 17850200 DOI: 10.1586/17434440.4.5.663] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The subthalamic nucleus (STN) is the primary target for the chronic deep brain stimulation treatment of Parkinson's disease. STN neurons exhibit a variety of characteristic properties that may play a key role in the overall population response to deep brain stimulation. Neuroinformatics techniques, in particular computational modeling, provide a method of bringing together pharmacological phenomena, such as the loss of dopamine, with electrophysiological characteristics. Developing accurate models of STN neurons plays an important part in the process of uncovering the link between the changes in STN pharmacology, physiology and synaptic input that occurs with Parkinson's disease and the effectiveness of treatments targeting the STN. We review a general procedure for developing computational models and present a model of STN neurons that reveals important membrane channel interactions. In particular, changes in these channel interactions under parkinsonian conditions may underlie changes in characteristic physiology, critical in determining the mechanisms of deep brain stimulation.
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Affiliation(s)
- Andrew Gillies
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh EH1 2QL, UK.
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36
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Belujon P, Bezard E, Taupignon A, Bioulac B, Benazzouz A. Noradrenergic modulation of subthalamic nucleus activity: behavioral and electrophysiological evidence in intact and 6-hydroxydopamine-lesioned rats. J Neurosci 2007; 27:9595-606. [PMID: 17804620 PMCID: PMC6672980 DOI: 10.1523/jneurosci.2583-07.2007] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The subthalamic nucleus (STN) plays a key role in the pathophysiology of Parkinson's disease. The modulation of the STN by norepinephrine, however, is unknown. The present study aims at characterizing the effects of systemic administration of noradrenergic agents on locomotor activity and on in vivo extracellularly recorded STN neuronal activity in intact and 6-hydroxydopamine (6-OHDA)-lesioned rats. Using selective agonists and antagonists of alpha1 and alpha2 adrenergic receptors (ARs), we show that STN neurons have functional alpha1- and alpha2-AR controlling STN firing with an impact on locomotor activity. We further demonstrate that those systemic effects are supported, at least in part, by a direct modulation of STN neuronal activity, using patch-clamp recordings of STN neurons in brain slices. These findings support the premise that hypokinesia is associated with an increased STN neuronal activity, and that improvements of parkinsonian motor abnormalities are associated with a decrease in STN activity. Our data challenge assumptions about the role of alpha1-AR and alpha2-AR in the regulation of STN neurons in both intact and 6-OHDA-lesioned rats and further ground the rationale for using alpha2-AR noradrenergic antagonists in Parkinson's disease, albeit via an unexpected mechanism.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Behavior, Animal/drug effects
- Electrophysiology
- Hypokinesia/chemically induced
- Hypokinesia/physiopathology
- Immunohistochemistry
- Male
- Medial Forebrain Bundle/drug effects
- Motor Activity/drug effects
- Neurons/drug effects
- Neurons/metabolism
- Norepinephrine/metabolism
- Organ Culture Techniques
- Oxidopamine
- Parkinsonian Disorders/chemically induced
- Parkinsonian Disorders/physiopathology
- Patch-Clamp Techniques
- Rats
- Rats, Wistar
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/metabolism
- Subthalamic Nucleus/drug effects
- Subthalamic Nucleus/metabolism
- Synaptic Transmission/drug effects
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Affiliation(s)
- Pauline Belujon
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Université Victor Segalen, 33076 Bordeaux Cedex, France
| | - Erwan Bezard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Université Victor Segalen, 33076 Bordeaux Cedex, France
| | - Anne Taupignon
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Université Victor Segalen, 33076 Bordeaux Cedex, France
| | - Bernard Bioulac
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Université Victor Segalen, 33076 Bordeaux Cedex, France
| | - Abdelhamid Benazzouz
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5227, Université Victor Segalen, 33076 Bordeaux Cedex, France
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37
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Ibáñez-Sandoval O, Carrillo-Reid L, Galarraga E, Tapia D, Mendoza E, Gomora JC, Aceves J, Bargas J. Bursting in substantia nigra pars reticulata neurons in vitro: possible relevance for Parkinson disease. J Neurophysiol 2007; 98:2311-23. [PMID: 17715194 DOI: 10.1152/jn.00620.2007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Projection neurons of the substantia nigra reticulata (SNr) convey basal ganglia (BG) processing to thalamocortical and brain stem circuits responsible for movement. Two models try to explain pathological BG performance during Parkinson disease (PD): the rate model, which posits an overexcitation of SNr neurons due to hyperactivity in the indirect pathway and hypoactivity of the direct pathway, and the oscillatory model, which explains PD as the product of pathological pattern generators disclosed by dopamine reduction. These models are, apparently, incompatible. We tested the predictions of the rate model by increasing the excitatory drive and reducing the inhibition on SNr neurons in vitro. This was done pharmacologically with bath application of glutamate agonist N-methyl-d-aspartate and GABA(A) receptor blockers, respectively. Both maneuvers induced bursting behavior in SNr neurons. Therefore synaptic changes forecasted by the rate model induce the electrical behavior predicted by the oscillatory model. In addition, we found evidence that Ca(V)3.2 Ca(2+) channels are a critical step in generating the bursting firing pattern in SNr neurons. Other ion channels involved are: hyperpolarization-activated cation channels, high-voltage-activated Ca(2+) channels, and Ca(2+)-activated K(+) channels. However, although these channels shape the temporal structure of bursting, only Ca(V)3.2 Ca(2+) channels are indispensable for the initiation of the bursting pattern.
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Affiliation(s)
- Osvaldo Ibáñez-Sandoval
- Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México City, México
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38
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Teruyama R, Armstrong WE. Calcium-dependent fast depolarizing afterpotentials in vasopressin neurons in the rat supraoptic nucleus. J Neurophysiol 2007; 98:2612-21. [PMID: 17715195 DOI: 10.1152/jn.00599.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Oxytocin (OT) and vasopressin (VP) synthesizing magnocellular cells (MNCs) in the supraoptic nucleus (SON) display distinct firing patterns during the physiological demands for these hormones. Depolarizing afterpotentials (DAPs) in these neurons are involved in controlling phasic bursting in VP neurons. Our whole cell recordings demonstrated a Cs(+)-resistant fast DAP (fDAP; decay tau = approximately 200 ms), which has not been previously reported, in addition to the well-known Cs(+)-sensitive slower DAP (sDAP; decay tau = approximately 2 s). Immunoidentification of recorded neurons revealed that all VP neurons, but only 20% of OT neurons, expressed the fDAP. The activation of the fDAP required influx of Ca(2+) through voltage-gated Ca(2+) channels as it was strongly suppressed in Ca(2+)-free extracellular solution or by bath application of Cd(2+). Additionally, the current underlying the fDAP (I(fDAP)) is a Ca(2+)-activated current rather than a Ca(2+) current per se as it was abolished by strongly buffering intracellular Ca(2+) with BAPTA. The I-V relationship of the I(fDAP) was linear at potentials less than -60 mV but showed pronounced outward rectification near -50 mV. I(fDAP) is sensitive to changes in extracellular Na(+) and K(+) but not Cl(-). A blocker of Ca(2+)-activated nonselective cation (CAN) currents, flufenamic acid, blocked the fDAP, suggesting the involvement of a CAN current in the generation of fDAP in VP neurons. We speculate that the two DAPs have different roles in generating after burst discharges and could play important roles in determining the distinct firing properties of VP neurons in the SON neurons.
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Affiliation(s)
- Ryoichi Teruyama
- Department of Anatomy and Neurobiology, University of Tennessee, Health Science Center, TN 38163, USA.
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39
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Lee CR, Tepper JM. A calcium-activated nonselective cation conductance underlies the plateau potential in rat substantia nigra GABAergic neurons. J Neurosci 2007; 27:6531-41. [PMID: 17567814 PMCID: PMC6672447 DOI: 10.1523/jneurosci.1678-07.2007] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Plateau potentials can be elicited in nigral GABAergic neurons by injection of 500 ms depolarizing current pulses from hyperpolarized holding potentials in whole-cell recordings in vitro. In approximately one-third of these neurons, plateau potentials were observed under control conditions and could be elicited in the remaining neurons after blocking potassium conductances. Application of the L-type calcium channel agonist Bay K 8644 or activation of NMDA receptors enhanced plateau potentials observed under control conditions and caused a plateau to be elicited in neurons not exhibiting it previously. The plateau potential was abolished in calcium-free buffer, as well as by nickel or cadmium. The L-type calcium channel blockers nimodipine and nifedipine abolished the plateau potential observed under control conditions but did not affect plateaus unmasked by tetraethylammonium. Plateau potentials observed under control conditions as well as those observed in the presence of Bay K 8644, NMDA, or tetraethylammonium were abolished in low-sodium buffer and by the calcium-activated nonselective cation conductance blocker flufenamic acid. These data suggest that nigral plateau potentials are mediated by a calcium-activated nonselective cation conductance (I(CAN)) that is activated by calcium entry predominantly through L-type calcium channels. In many nigral neurons, I(CAN) is masked by tetraethylammonium-sensitive potassium conductances, but plateaus can be evoked after increasing calcium conductances. The I(CAN)-mediated plateau potential in nigral GABAergic neurons likely affects the way these neurons integrate input and may represent a mechanism contributing to the rhythmic firing of these neurons seen in pathological conditions such as Parkinson's disease.
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Affiliation(s)
- Christian R. Lee
- Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102
| | - James M. Tepper
- Center for Molecular and Behavioral Neuroscience, Rutgers, The State University of New Jersey, Newark, New Jersey 07102
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40
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Shen KZ, Kozell LB, Johnson SW. Multiple conductances are modulated by 5-HT receptor subtypes in rat subthalamic nucleus neurons. Neuroscience 2007; 148:996-1003. [PMID: 17706881 PMCID: PMC2034448 DOI: 10.1016/j.neuroscience.2007.07.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Revised: 06/28/2007] [Accepted: 08/03/2007] [Indexed: 11/16/2022]
Abstract
Firing patterns of subthalamic nucleus (STN) neurons influence normal and abnormal movements. The STN expresses multiple 5-HT receptor subtypes that may regulate neuronal excitability. We used whole-cell patch-clamp recordings to characterize 5-HT receptor-mediated effects on membrane currents in STN neurons in rat brain slices. In 80 STN neurons under voltage-clamp (-70 mV), 5-HT (30 microM) evoked inward currents in 64%, outward currents in 17%, and biphasic currents in 19%. 5-HT-induced outward current was caused by an increased K(+) conductance (1.4+/-0.2 nS) and was blocked by the 5-HT(1A) antagonist WAY 100135. The 5-HT-evoked inward current, which was blocked by antagonists at 5-HT(2C) and/or 5-HT(4) receptors, had two types of current-voltage (I-V) relations. Currents associated with the type 1 I-V relation showed negative slope conductance at potentials <-110 mV and were occluded by Ba(2+). In contrast, the type 2 I-V relation appeared linear and had positive slope conductance (0.64+/-0.11 nS). Type 2 inward currents were Ba(2+)-insensitive, and the reversal potential of -19 mV suggests a mixed cation conductance. In STN neurons in which 5-HT evoked inward currents, 5-HT potentiated burst firing induced by N-methyl-d-aspartate (NMDA). But in neurons in which 5-HT evoked outward current, 5-HT slowed NMDA-dependent burst firing. We conclude that 5-HT receptor subtypes can differentially regulate firing pattern by modulating multiple conductances in STN neurons.
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Affiliation(s)
- K-Z Shen
- Department of Neurology, Oregon Health and Science University, Portland, OR 97239, USA
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41
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Chung YH, Kim D, Moon NJ, Oh CS, Lee E, Shin DH, Kim SS, Lee WB, Lee JY, Cha CI. Immunohistochemical study on the distribution of canonical transient receptor potential channels in rat basal ganglia. Neurosci Lett 2007; 422:18-23. [PMID: 17590510 DOI: 10.1016/j.neulet.2007.05.042] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 04/23/2007] [Accepted: 05/07/2007] [Indexed: 01/24/2023]
Abstract
In the present study, we examined the localizations of canonical transient receptor potential channels (TRPCs) in rat basal ganglia. The dot-like staining pattern of TRPC5 was observed through the globus pallidus (GP) and caudate-putamen. TRPC7 had a strikingly high level of expression in the neuropil in the GP. In the subthalamic nucleus, strong staining for TRPC5 was observed in the cell bodies, while moderate to high immunoreactivies for TRPC1, TRPC3, TRPC4 and TRPC7 were found in the cell bodies and surrounding neuropil. In the substantia nigra, immunoreactivities for TRPC3 and TRPC7 were prominent in the cell bodies and several processes in the pars compacta and pars reticulata. TRPC6 was expressed in the neuropil, not in the cell bodies. This study may provide useful data for the future investigations on the structural and functional properties of TRPCs.
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Affiliation(s)
- Yoon Hee Chung
- Department of Anatomy, College of Medicine, Chung-Ang University, 221 Heukseok-Dong, Dongjak-Gu, Seoul 156-756, South Korea
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42
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Komendantov AO, Trayanova NA, Tasker JG. Somato-dendritic mechanisms underlying the electrophysiological properties of hypothalamic magnocellular neuroendocrine cells: a multicompartmental model study. J Comput Neurosci 2007; 23:143-68. [PMID: 17484044 PMCID: PMC2837924 DOI: 10.1007/s10827-007-0024-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2005] [Revised: 01/27/2007] [Accepted: 02/07/2007] [Indexed: 01/08/2023]
Abstract
Magnocellular neuroendocrine cells (MNCs) of the hypothalamus synthesize the neurohormones vasopressin and oxytocin, which are released into the blood and exert a wide spectrum of actions, including the regulation of cardiovascular and reproductive functions. Vasopressin- and oxytocin-secreting neurons have similar morphological structure and electrophysiological characteristics. A realistic multicompartmental model of a MNC with a bipolar branching structure was developed and calibrated based on morphological and in vitro electrophysiological data in order to explore the roles of ion currents and intracellular calcium dynamics in the intrinsic electrical MNC properties. The model was used to determine the likely distributions of ion conductances in morphologically distinct parts of the MNCs: soma, primary dendrites and secondary dendrites. While reproducing the general electrophysiological features of MNCs, the model demonstrates that the differential spatial distributions of ion channels influence the functional expression of MNC properties, and reveals the potential importance of dendritic conductances in these properties.
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43
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Pace RW, Mackay DD, Feldman JL, Del Negro CA. Inspiratory bursts in the preBötzinger complex depend on a calcium-activated non-specific cation current linked to glutamate receptors in neonatal mice. J Physiol 2007; 582:113-25. [PMID: 17446214 PMCID: PMC2075310 DOI: 10.1113/jphysiol.2007.133660] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Inspiratory neurons of the preBötzinger complex (preBötC) form local excitatory networks and display 10-30 mV transient depolarizations, dubbed inspiratory drive potentials, with superimposed spiking. AMPA receptors are critical for rhythmogenesis under normal conditions in vitro but whether other postsynaptic mechanisms contribute to drive potential generation remains unknown. We examined synaptic and intrinsic membrane properties that generate inspiratory drive potentials in preBötC neurons using neonatal mouse medullary slice preparations that generate respiratory rhythm. We found that NMDA receptors, group I metabotropic glutamate receptors (mGluRs), but not group II mGluRs, contributed to inspiratory drive potentials. Subtype 1 of the group I mGluR family (mGluR1) probably regulates a K+ channel, whereas mGluR5 operates via an inositol 1,4,5-trisphosphate (IP3) receptor-dependent mechanism to augment drive potential generation. We tested for and verified the presence of a Ca2+-activated non-specific cation current (I(CAN)) in preBötC neurons. We also found that high concentrations of intracellular BAPTA, a high-affinity Ca2+ chelator, and the I(CAN) antagonist flufenamic acid (FFA) decreased the magnitude of drive potentials. We conclude that I(CAN) underlies robust inspiratory drive potentials in preBötC neurons, and is only fully evoked by ionotropic and metabotropic glutamatergic synaptic inputs, i.e. by network activity.
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MESH Headings
- Action Potentials
- Animals
- Animals, Newborn
- Calcium/metabolism
- Calcium Signaling
- Chelating Agents/pharmacology
- Egtazic Acid/analogs & derivatives
- Egtazic Acid/pharmacology
- Flufenamic Acid/pharmacology
- Glutamic Acid/metabolism
- In Vitro Techniques
- Inhalation/drug effects
- Inhalation/physiology
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Kinetics
- Mice
- Mice, Inbred C57BL
- Neurons/drug effects
- Neurons/metabolism
- Periodicity
- Receptor, Metabotropic Glutamate 5
- Receptors, AMPA/metabolism
- Receptors, Glutamate/drug effects
- Receptors, Glutamate/metabolism
- Receptors, Metabotropic Glutamate/metabolism
- Receptors, N-Methyl-D-Aspartate/metabolism
- Respiratory Center/cytology
- Respiratory Center/drug effects
- Respiratory Center/metabolism
- Synapses/drug effects
- Synapses/metabolism
- Synaptic Transmission/drug effects
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Affiliation(s)
- Ryland W Pace
- Department of Applied Science, McGlothlin-Street Hall, Room 303, The College of William and Mary, Williamsburg, VA 23187-8795, USA
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44
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Galvan A, Kuwajima M, Smith Y. Glutamate and GABA receptors and transporters in the basal ganglia: what does their subsynaptic localization reveal about their function? Neuroscience 2006; 143:351-75. [PMID: 17059868 PMCID: PMC2039707 DOI: 10.1016/j.neuroscience.2006.09.019] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Revised: 09/10/2006] [Accepted: 09/13/2006] [Indexed: 01/29/2023]
Abstract
GABA and glutamate, the main transmitters in the basal ganglia, exert their effects through ionotropic and metabotropic receptors. The dynamic activation of these receptors in response to released neurotransmitter depends, among other factors, on their precise localization in relation to corresponding synapses. The use of high resolution quantitative electron microscope immunocytochemical techniques has provided in-depth description of the subcellular and subsynaptic localization of these receptors in the CNS. In this article, we review recent findings on the ultrastructural localization of GABA and glutamate receptors and transporters in monkey and rat basal ganglia, at synaptic, extrasynaptic and presynaptic sites. The anatomical evidence supports numerous potential locations for receptor-neurotransmitter interactions, and raises important questions regarding mechanisms of activation and function of synaptic versus extrasynaptic receptors in the basal ganglia.
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Affiliation(s)
- A Galvan
- Yerkes National Primate Research Center, Emory University, Atlanta, GA 30322, USA.
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45
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Gillies A, Willshaw D. Membrane Channel Interactions Underlying Rat Subthalamic Projection Neuron Rhythmic and Bursting Activity. J Neurophysiol 2006; 95:2352-65. [PMID: 16148272 DOI: 10.1152/jn.00525.2005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A computational model of the rat subthalamic nucleus projection neuron is constructed using electrophysiological and morphological data and a restricted set of channel specifications. The model cell exhibits a wide range of electrophysiological behaviors characteristic of rat subthalamic neurons. It reveals that a key set of three channels play a primary role in distinguishing behaviors: a high-voltage-activated calcium channel (Cav1.2.-1.3), a low-voltage-activated calcium channel (Cav3.-), and a small current calcium-activated potassium channel (KCa2.1–2.3). Short and long posthyperpolarization rebound responses, low-frequency rhythmic bursting (<1 Hz), higher-frequency rhythmic bursting (4–7 Hz), and slow action and depolarizing potentials are behaviors all mediated by the interaction of these channels. This interaction can generate a robust calcium-dependent extended depolarization in the dendrites (a depolarizing plateau). The diversity observed in the rat subthalamic physiology (such as short or long rebounds, or the presence of low-frequency rhythmic busting) can arise from alterations in both the density and distributions of these channel types and, consequently, their ability to generate this depolarizing plateau. A number of important predictions arise from the model. For example, blocking or disrupting the low-voltage-activated Cav3.- calcium current should mute the emergence of rebound responses and rhythmic bursting. Conversely, increasing this channel current via large hyperpolarizing potentials in combination with partial blockade of the high-voltage-activated calcium channels should lead to the more experimentally elusive in vitro high-frequency bursting.
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Affiliation(s)
- Andrew Gillies
- Institute for Adaptive and Neural Computation, School of Informatics, University of Edinburgh, Edinburgh, United Kingdom.
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46
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Kass JI, Mintz IM. Silent plateau potentials, rhythmic bursts, and pacemaker firing: three patterns of activity that coexist in quadristable subthalamic neurons. Proc Natl Acad Sci U S A 2005; 103:183-8. [PMID: 16373507 PMCID: PMC1324981 DOI: 10.1073/pnas.0506781102] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Subthalamic neurons display uncommon intrinsic behaviors that are likely to contribute to the motor and cognitive functions of the basal ganglia and to many of its disorders. Here, we report silent plateau potentials in these cells. These plateau responses start with a transient burst of action potentials that quickly diminish in amplitude because of spike inactivation and current shunt. The resulting interruption of spiking reveals a stable depolarization (up state) that clamps the cell membrane potential near -40 mV for several seconds. These plateau potentials coexist in single subthalamic neurons with more familiar patterns of burst and pacemaker firing. Within a narrow range of baseline membrane potentials (-67 to -60 mV), depolarization abruptly switches single cells from bistable to rhythmic bursts or tonic firing modes, thus selecting entirely distinct algorithms for integrating cortical and pallidal synaptic inputs.
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Affiliation(s)
- Jason I Kass
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
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Baufreton J, Zhu ZT, Garret M, Bioulac B, Johnson SW, Taupignon AI. Dopamine receptors set the pattern of activity generated in subthalamic neurons. FASEB J 2005; 19:1771-7. [PMID: 16260646 DOI: 10.1096/fj.04-3401hyp] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Information processing in the brain requires adequate background neuronal activity. As Parkinson's disease progresses, patients typically become akinetic; the death of dopaminergic neurons leads to a dopamine-depleted state, which disrupts information processing related to movement in a brain area called the basal ganglia. Using agonists of dopamine receptors in the D1 and D2 families on rat brain slices, we show that dopamine receptors in these two families govern the firing pattern of neurons in the subthalamic nucleus, a crucial part of the basal ganglia. We propose a conceptual frame, based on specific properties of dopamine receptors, to account for the dominance of different background firing patterns in normal and dopamine-depleted states.
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Affiliation(s)
- J Baufreton
- UMR 5543, University Victor Segalen, Bordeaux, France
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Loucif KC, Wilson CL, Baig R, Lacey MG, Stanford IM. Functional interconnectivity between the globus pallidus and the subthalamic nucleus in the mouse brain slice. J Physiol 2005; 567:977-87. [PMID: 16037086 PMCID: PMC1474218 DOI: 10.1113/jphysiol.2005.093807] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/29/2005] [Accepted: 07/14/2005] [Indexed: 11/08/2022] Open
Abstract
In accordance with its central role in basal ganglia circuitry, changes in the rate of action potential firing and pattern of activity in the globus pallidus (GP)-subthalamic nucleus (STN) network are apparent in movement disorders. In this study we have developed a mouse brain slice preparation that maintains the functional connectivity between the GP and STN in order to assess its role in shaping and modulating bursting activity promoted by pharmacological manipulations. Fibre-tract tracing studies indicated that a parasagittal slice cut 20 deg to the midline best preserved connectivity between the GP and the STN. IPSCs and EPSCs elicited by electrical stimulation confirmed connectivity from GP to STN in 44/59 slices and from STN to GP in 22/33 slices, respectively. In control slices, 74/76 (97%) of STN cells fired tonically at a rate of 10.3 +/- 1.3 Hz. This rate and pattern of single spiking activity was unaffected by bath application of the GABA(A) antagonist picrotoxin (50 microM, n = 9) or the glutamate receptor antagonist (6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX) 10 microM, n = 8). Bursting activity in STN neurones could be induced pharmacologically by application of NMDA alone (20 microm, 3/18 cells, 17%) but was more robust if NMDA was applied in conjunction with apamin (20-100 nM, 34/77 cells, 44%). Once again, neither picrotoxin (50 microM, n = 5) nor CNQX (10 microM, n = 5) had any effect on the frequency or pattern of the STN neurone activity while paired STN and GP recordings of tonic and bursting activity show no evidence of coherent activity. Thus, in a mouse brain slice preparation where functional GP-STN connectivity is preserved, no regenerative synaptically mediated activity indicative of a dynamic network is evident, either in the resting state or when neuronal bursting in both the GP and STN is generated by application of NMDA/apamin. This difference from the brain in Parkinson's disease may be attributed either to insufficient preservation of cortico-striato-pallidal or cortico-subthalamic circuitry, and/or an essential requirement for adaptive changes resulting from dopamine depletion for the expression of network activity within this tissue complex.
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Affiliation(s)
- K C Loucif
- School of Life and Health Sciences, Aston University, Birmingham, UK
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Lüke M, Henry M, Lingohr T, Maghsoodian M, Hescheler J, Weiergräber M, Sickel W, Schneider T. A Ni2+-sensitive component of the ERG b-wave from the isolated bovine retina is related to E-type voltage-gated Ca2+ channels. Graefes Arch Clin Exp Ophthalmol 2005; 243:933-41. [PMID: 15838665 DOI: 10.1007/s00417-005-1145-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2004] [Revised: 11/29/2004] [Accepted: 01/14/2005] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Voltage-dependent Ca(2+) channels trigger and control important cellular processes like neurotransmitter release and secretion, long-term potentiation, and gene expression in excitable cells. During retinal signal perception and processing, presynaptic Ca(2+) channels facilitate neurotransmitter release in photoreceptors and bipolar neurons, at nonspiking synapses which generate graded potentials. METHODS The nature of voltage-gated Ca(2+) channels involved in retinal signal transduction is investigated in the present report by recording the electroretinogram (ERG) from the isolated and perfused bovine retina. Transcripts of the E/R- and T-type Ca(2+) channels are detected by RT-PCR. RESULTS Using the Ca(2+) channel antagonists (+/-)-isradipine, NiCl(2), mibefradil, and SNX-482 results in either stimulatory or inhibitory effects on the ERG b-wave amplitude. On the transcript level, mRNA is detected for the E/R-type and a T-type voltage-gated Ca(2+) channel containing Ca(v)2.3 and Ca(v)3.1 as ion-conducting subunits, respectively. CONCLUSION Blocking of the E/R-type Ca(2+) channels by NiCl(2) (10 microM) and SNX-482 (30 nM) contributes to the stimulatory effect, whereas antagonism of T-type as well as L-type Ca(2+) channels meditates the inhibitory action on the b-wave amplitude. Thus, a novel function for E/R-type voltage-gated Ca(2+) channels is probably associated with the visual signal transduction in the mammalian retina.
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Affiliation(s)
- Matthias Lüke
- Institute of Neurophysiology, University of Cologne, Robert-Koch Str. 39, 50931 Cologne, Germany
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Shen KZ, Johnson SW. Dopamine depletion alters responses to glutamate and GABA in the rat subthalamic nucleus. Neuroreport 2005; 16:171-4. [PMID: 15671871 DOI: 10.1097/00001756-200502080-00021] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We used whole-cell recordings to compare currents evoked by glutamate and GABA receptor agonists in subthalamic nucleus neurons located ipsilateral and contralateral to unilateral 6-hydroxydopamine (6-OHDA) injections into the substantia nigra zona compacta. The ratio of currents evoked by AMPA (0.6 microM) and NMDA (20 microM) was significantly greater in neurons recorded ipsilateral to 6-OHDA lesions compared with the ratio of currents recorded in control (contralateral) neurons. Both the GABA(A) agonist isoguvacine (20 microM) and the GABA(B) agonist baclofen (10 microM) evoked significantly greater outward currents in subthalamic nucleus neurons ipsilateral to the lesion compared to contralateral neurons. We conclude that chronic dopamine depletion up-regulates expression of GABA receptors and shifts the functional expression of ionotropic glutamate receptor subtype from NMDA to AMPA receptors in subthalamic nucleus.
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Affiliation(s)
- Ke-Zhong Shen
- 1Department of Neurology, Oregon Health and Science University, Portland, OR 97239, USA
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