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Higgs MH, Beckstead MJ. Impact of Unitary Synaptic Inhibition on Spike Timing in Ventral Tegmental Area Dopamine Neurons. eNeuro 2024; 11:ENEURO.0203-24.2024. [PMID: 38969500 PMCID: PMC11287791 DOI: 10.1523/eneuro.0203-24.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Revised: 06/25/2024] [Accepted: 06/28/2024] [Indexed: 07/07/2024] Open
Abstract
Midbrain dopamine neurons receive convergent synaptic input from multiple brain areas, which perturbs rhythmic pacemaking to produce the complex firing patterns observed in vivo. This study investigated the impact of single and multiple inhibitory inputs on ventral tegmental area (VTA) dopamine neuron firing in mice of both sexes using novel experimental measurements and modeling. We first measured unitary inhibitory postsynaptic currents produced by single axons using both minimal electrical stimulation and minimal optical stimulation of rostromedial tegmental nucleus and ventral pallidum afferents. We next determined the phase resetting curve, the reversal potential for GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs), and the average interspike membrane potential trajectory during pacemaking. We combined these data in a phase oscillator model of a VTA dopamine neuron, simulating the effects of unitary inhibitory postsynaptic conductances (uIPSGs) on spike timing and rate. The effect of a uIPSG on spike timing was predicted to vary according to its timing within the interspike interval or phase. Simulations were performed to predict the pause duration resulting from the synchronous arrival of multiple uIPSGs and the changes in firing rate and regularity produced by asynchronous uIPSGs. The model data suggest that asynchronous inhibition is more effective than synchronous inhibition, because it tends to hold the neuron at membrane potentials well positive to the IPSC reversal potential. Our results indicate that small fluctuations in the inhibitory synaptic input arriving from the many afferents to each dopamine neuron are sufficient to produce highly variable firing patterns, including pauses that have been implicated in reinforcement.
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Affiliation(s)
- Matthew H Higgs
- Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
| | - Michael J Beckstead
- Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK 73104
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Aristieta A, Parker JE, Gao YE, Rubin JE, Gittis AH. Dopamine depletion weakens direct pathway modulation of SNr neurons. Neurobiol Dis 2024; 196:106512. [PMID: 38670278 DOI: 10.1016/j.nbd.2024.106512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2024] [Revised: 04/13/2024] [Accepted: 04/23/2024] [Indexed: 04/28/2024] Open
Abstract
Neurons in the substantia nigra reticulata (SNr) transmit information about basal ganglia output to dozens of brain regions in thalamocortical and brainstem motor networks. Activity of SNr neurons is regulated by convergent input from upstream basal ganglia nuclei, including GABAergic inputs from the striatum and the external globus pallidus (GPe). GABAergic inputs from the striatum convey information from the direct pathway, while GABAergic inputs from the GPe convey information from the indirect pathway. Chronic loss of dopamine, as occurs in Parkinson's disease, disrupts the balance of direct and indirect pathway neurons at the level of the striatum, but the question of how dopamine loss affects information propagation along these pathways outside of the striatum is less well understood. Using a combination of in vivo and slice electrophysiology, we find that dopamine depletion selectively weakens the direct pathway's influence over neural activity in the SNr due to changes in the decay kinetics of GABA-mediated synaptic currents. GABAergic signaling from GPe neurons in the indirect pathway was not affected, resulting in an inversion of the normal balance of inhibitory control over basal ganglia output through the SNr. These results highlight the contribution of cellular mechanisms outside of the striatum that impact the responses of basal ganglia output neurons to the direct and indirect pathways in disease.
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Affiliation(s)
- Asier Aristieta
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - John E Parker
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Ya Emma Gao
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Jonathan E Rubin
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Aryn H Gittis
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA; Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
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3
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Liang E, Chen Y, Yan Y, Wang S, Yuan J, Yu T. Role of the substantia nigra pars reticulata in sleep-wakefulness: A review of research progress. Sleep Med 2024; 113:284-292. [PMID: 38071927 DOI: 10.1016/j.sleep.2023.11.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/14/2023] [Accepted: 11/21/2023] [Indexed: 01/07/2024]
Abstract
Sleep is a complex physiological process that includes two main stages: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. During mammalian sleep, especially REM sleep, skeletal muscles are suppressed to varying degrees, and corresponding movements are inhibited. The synchronous occurrence of sleep and motor inhibition suggests they may share the same neural circuits. Recently, the substantia nigra pars reticulata (SNr) has attracted attention for its potential dual role in regulating sleep-wake cycles and movement. In this review, the SNr's role is surveyed by examining existing research reports regarding its involvement in sleep-wake regulation and motor control. By focusing on the SNr, the goal is to shed light on its dual role intricacies and stimulate further inquiry into potential interactions between sleep and movement regulation, thus aiming to explore sleep-wake regulatory mechanisms and offer novel directions for subsequent scientific investigation.
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Affiliation(s)
- Enpeng Liang
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China; Department of Pain Medicine, The First Affiliated Hospital of Zunyi Medical University, Zunyi, 563000, China
| | - Ya Chen
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China
| | - Yan Yan
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China
| | - Siwei Wang
- Department of Dental Implantology, The Affiliated Stomatological Hospital of Zunyi Medical University, 563000, Zunyi, China
| | - Jie Yuan
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China; Department of Pain Medicine, The First Affiliated Hospital of Zunyi Medical University, Zunyi, 563000, China; Department of Anesthesiology, The First Affiliated Hospital of Zunyi Medical University, Zunyi, 563000, China.
| | - Tian Yu
- Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, 563000, China; Guizhou Key Laboratory of Brain Science, Zunyi Medical University, Zunyi, 563000, China.
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4
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Wilson CJ, Jones JA. Propagation of Oscillations in the Indirect Pathway of the Basal Ganglia. J Neurosci 2023; 43:6112-6125. [PMID: 37400253 PMCID: PMC10476642 DOI: 10.1523/jneurosci.0445-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/22/2023] [Accepted: 06/23/2023] [Indexed: 07/05/2023] Open
Abstract
Oscillatory signals propagate in the basal ganglia from prototypic neurons in the external globus pallidus (GPe) to their target neurons in the substantia nigra pars reticulata (SNr), internal pallidal segment, and subthalamic nucleus. Neurons in the GPe fire spontaneously, so oscillatory input signals can be encoded as changes in timing of action potentials within an ongoing spike train. When GPe neurons were driven by an oscillatory current in male and female mice, these spike-timing changes produced spike-oscillation coherence over a range of frequencies extending at least to 100 Hz. Using the known kinetics of the GPe→SNr synapse, we calculated the postsynaptic currents that would be generated in SNr neurons from the recorded GPe spike trains. The ongoing synaptic barrage from spontaneous firing, frequency-dependent short-term depression, and stochastic fluctuations at the synapse embed the input oscillation into a noisy sequence of synaptic currents in the SNr. The oscillatory component of the resulting synaptic current must compete with the noisy spontaneous synaptic barrage for control of postsynaptic SNr neurons, which have their own frequency-dependent sensitivities. Despite this, SNr neurons subjected to synaptic conductance changes generated from recorded GPe neuron firing patterns also became coherent with oscillations over a broad range of frequencies. The presynaptic, synaptic, and postsynaptic frequency sensitivities were all dependent on the firing rates of presynaptic and postsynaptic neurons. Firing rate changes, often assumed to be the propagating signal in these circuits, do not encode most oscillation frequencies, but instead determine which signal frequencies propagate effectively and which are suppressed.SIGNIFICANCE STATEMENT Oscillations are present in all the basal ganglia nuclei, include a range of frequencies, and change over the course of learning and behavior. Exaggerated oscillations are a hallmark of basal ganglia pathologies, and each has a specific frequency range. Because of its position as a hub in the basal ganglia circuitry, the globus pallidus is a candidate origin for oscillations propagating between nuclei. We imposed low-amplitude oscillations on individual globus pallidus neurons at specific frequencies and measured the coherence between the oscillation and firing as a function of frequency. We then used these responses to measure the effectiveness of oscillatory propagation to other basal ganglia nuclei. Propagation was effective for oscillation frequencies as high as 100 Hz.
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Affiliation(s)
- Charles J Wilson
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
| | - James A Jones
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
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Jones JA, Higgs MH, Olivares E, Peña J, Wilson CJ. Spontaneous Activity of the Local GABAergic Synaptic Network Causes Irregular Neuronal Firing in the External Globus Pallidus. J Neurosci 2023; 43:1281-1297. [PMID: 36623877 PMCID: PMC9987574 DOI: 10.1523/jneurosci.1969-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/22/2022] [Accepted: 01/03/2023] [Indexed: 01/11/2023] Open
Abstract
Autonomously firing GABAergic neurons in the external globus pallidus (GPe) form a local synaptic network. In slices, most GPe neurons receive a continuous inhibitory synaptic barrage from 1 or 2 presynaptic GPe neurons. We measured the barrage's effect on the firing rate and regularity of GPe neurons in male and female mice using perforated patch recordings. Silencing the firing of parvalbumin-positive (PV+) GPe neurons by activating genetically expressed Archaerhodopsin current increased the firing rate and regularity of PV- neurons. In contrast, silencing Npas1+ GPe neurons with Archaerhodopsin had insignificant effects on Npas1- neuron firing. Blocking spontaneous GABAergic synaptic input with gabazine reproduced the effects of silencing PV+ neuron firing on the firing rate and regularity of Npas1+ neurons and had similar effects on PV+ neuron firing. To simulate the barrage, we constructed conductance waveforms for dynamic clamp based on experimentally measured inhibitory postsynaptic conductance trains from 1 or 2 unitary local connections. The resulting inhibition replicated the effect on firing seen in the intact active network in the slice. We then increased the number of unitary inputs to match estimates of local network connectivity in vivo As few as 5 unitary inputs produced large increases in firing irregularity. The firing rate was also reduced initially, but PV+ neurons exhibited a slow spike-frequency adaptation that partially restored the rate despite sustained inhibition. We conclude that the irregular firing pattern of GPe neurons in vivo is largely due to the ongoing local inhibitory synaptic barrage produced by the spontaneous firing of other GPe neurons.SIGNIFICANCE STATEMENT Functional roles of local axon collaterals in the external globus pallidus (GPe) have remained elusive because of difficulty in isolating local inhibition from other GABAergic inputs in vivo, and in preserving the autonomous firing of GPe neurons and detecting their spontaneous local inputs in slices. We used perforated patch recordings to detect spontaneous local inputs during rhythmic firing. We found that the autonomous firing of single presynaptic GPe neurons produces inhibitory synaptic barrages that significantly alter the firing regularity of other GPe neurons. Our findings suggest that, although GPe neurons receive input from only a few other GPe neurons, each local connection has a large impact on their firing.
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Affiliation(s)
- James A. Jones
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
| | - Matthew H. Higgs
- Aging & Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| | - Erick Olivares
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
| | - Jacob Peña
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
| | - Charles J. Wilson
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, San Antonio, Texas 78249
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Lin M, Wang Y, Wang Y, Chen F. Electrical activation of the pedunculopontine tegmental nucleus modulates the neuronal activities of the subthalamic nucleus and the substantia nigra pars reticulata in anesthetized rats. J Neurosci Res 2022; 100:2090-2106. [DOI: 10.1002/jnr.25117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2022] [Revised: 06/28/2022] [Accepted: 07/24/2022] [Indexed: 11/09/2022]
Affiliation(s)
- Muxin Lin
- Bio‐X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education Shanghai Jiao Tong University Shanghai China
- Exercise, Health and Technology Centre, Department of Physical Education Shanghai Jiao Tong University Shanghai China
| | - Ying Wang
- Core Research Facilities Southern University of Science and Technology Shenzhen China
| | - Yi Wang
- Enlight Medical Technologies (Shanghai) Co., Ltd. Shanghai China
| | - Fujun Chen
- Bio‐X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education Shanghai Jiao Tong University Shanghai China
- Exercise, Health and Technology Centre, Department of Physical Education Shanghai Jiao Tong University Shanghai China
- WLA Laboratories, World Laureates Association Shanghai China
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Xu S, Deng Y, Luo J, Liu Y, He E, Yang Y, Zhang K, Sha L, Dai Y, Ming T, Song Y, Jing L, Zhuang C, Xu Q, Cai X. A Neural Sensor with a Nanocomposite Interface for the Study of Spike Characteristics of Hippocampal Neurons under Learning Training. BIOSENSORS 2022; 12:bios12070546. [PMID: 35884349 PMCID: PMC9312960 DOI: 10.3390/bios12070546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 07/19/2022] [Accepted: 07/19/2022] [Indexed: 11/16/2022]
Abstract
Both the cellular- and population-level properties of involved neurons are essential for unveiling the learning and memory functions of the brain. To give equal attention to these two aspects, neural sensors based on microelectrode arrays (MEAs) have been in the limelight due to their noninvasive detection and regulation capabilities. Here, we fabricated a neural sensor using carboxylated graphene/3,4-ethylenedioxythiophene:polystyrenesulfonate (cGO/PEDOT:PSS), which is effective in sensing and monitoring neuronal electrophysiological activity in vitro for a long time. The cGO/PEDOT:PSS-modified microelectrodes exhibited a lower electrochemical impedance (7.26 ± 0.29 kΩ), higher charge storage capacity (7.53 ± 0.34 mC/cm2), and improved charge injection (3.11 ± 0.25 mC/cm2). In addition, their performance was maintained after 2 to 4 weeks of long-term cell culture and 50,000 stimulation pulses. During neural network training, the sensors were able to induce learning function in hippocampal neurons through precise electrical stimulation and simultaneously detect changes in neural activity at multiple levels. At the cellular level, not only were three kinds of transient responses to electrical stimulation sensed, but electrical stimulation was also found to affect inhibitory neurons more than excitatory neurons. As for the population level, changes in connectivity and firing synchrony were identified. The cGO/PEDOT:PSS-based neural sensor offers an excellent tool in brain function development and neurological disease treatment.
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Affiliation(s)
- Shihong Xu
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Deng
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China; (Y.D.); (L.S.); (Q.X.)
| | - Jinping Luo
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yaoyao Liu
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Enhui He
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yan Yang
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kui Zhang
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Longze Sha
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China; (Y.D.); (L.S.); (Q.X.)
| | - Yuchun Dai
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tao Ming
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yilin Song
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Luyi Jing
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chengyu Zhuang
- Department of Orthopaedics, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China;
| | - Qi Xu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China; (Y.D.); (L.S.); (Q.X.)
| | - Xinxia Cai
- State Key Laboratory of Transducer Technology, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100190, China; (S.X.); (J.L.); (Y.L.); (E.H.); (Y.Y.); (K.Z.); (Y.D.); (T.M.); (Y.S.); (L.J.)
- School of Electronic, Electrical and Communication Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
- Correspondence:
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Olivares E, Higgs MH, Wilson CJ. Local inhibition in a model of the indirect pathway globus pallidus network slows and deregularizes background firing, but sharpens and synchronizes responses to striatal input. J Comput Neurosci 2022; 50:251-272. [PMID: 35274227 DOI: 10.1007/s10827-022-00814-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Revised: 02/17/2022] [Accepted: 02/24/2022] [Indexed: 11/24/2022]
Abstract
The external segment of globus pallidus (GPe) is a network of oscillatory neurons connected by inhibitory synapses. We studied the intrinsic dynamic and the response to a shared brief inhibitory stimulus in a model GPe network. Individual neurons were simulated using a phase resetting model based on measurements from mouse GPe neurons studied in slices. The neurons showed a broad heterogeneity in their firing rates and in the shapes and sizes of their phase resetting curves. Connectivity in the network was set to match experimental measurements. We generated statistically equivalent neuron heterogeneity in a small-world model, in which 99% of connections were made with near neighbors and 1% at random, and in a model with entirely random connectivity. In both networks, the resting activity was slowed and made more irregular by the local inhibition, but it did not show any periodic pattern. Cross-correlations among neuron pairs were limited to directly connected neurons. When stimulated by a shared inhibitory input, the individual neuron responses separated into two groups: one with a short and stereotyped period of inhibition followed by a transient increase in firing probability, and the other responding with a sustained inhibition. Despite differences in firing rate, the responses of the first group of neurons were of fixed duration and were synchronized across cells.
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Affiliation(s)
- Erick Olivares
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA
| | - Matthew H Higgs
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA
| | - Charles J Wilson
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, USA.
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9
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Higgs MH, Jones JA, Chan CS, Wilson CJ. Periodic unitary synaptic currents in the mouse globus pallidus during spontaneous firing in slices. J Neurophysiol 2021; 125:1482-1500. [PMID: 33729831 PMCID: PMC8424575 DOI: 10.1152/jn.00071.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/11/2021] [Accepted: 03/11/2021] [Indexed: 01/27/2023] Open
Abstract
Neurons in the external globus pallidus (GPe) are autonomous pacemakers, but their spontaneous firing is continually perturbed by synaptic input. Because GPe neurons fire rhythmically in slices, spontaneous inhibitory synaptic currents (IPSCs) should be evident there. We identified periodic series of IPSCs in slices, each corresponding to unitary synaptic currents from one presynaptic cell. Optogenetic stimulation of the striatal indirect pathway axons caused a pause and temporal resetting of the periodic input, confirming that it arose from local neurons subject to striatal inhibition. We determined the firing statistics of the presynaptic neurons from the unitary IPSC statistics and estimated their frequencies, peak amplitudes, and reliabilities. To determine what types of GPe neurons received the spontaneous inhibition, we recorded from genetically labeled parvalbumin (PV) and Npas1-expressing neurons. Both cell types received periodic spontaneous IPSCs with similar frequencies. Optogenetic inhibition of PV neurons reduced the spontaneous IPSC rate in almost all neurons with active unitary inputs, whereas inhibition of Npas1 neurons rarely affected the spontaneous IPSC rate in any neurons. These results suggest that PV neurons provided most of the active unitary inputs to both cell types. Optogenetic pulse stimulation of PV neurons at light levels that can activate cut axons yielded an estimate of connectivity in the fully connected network. The local network is a powerful source of inhibition to both PV and Npas1 neurons, which contributes to irregular firing and may influence the responses to external synaptic inputs.NEW & NOTEWORTHY Brain circuits are often quiet in slices. In the globus pallidus, network activity continues because of the neurons' rhythmic autonomous firing. In this study, synaptic currents generated by the network barrage were measured in single neurons. Unitary synaptic currents arising from single presynaptic neurons were identified by their unique periodicity. Periodic synaptic currents were large and reliable, even at the cell's natural firing rates, but arose from a small number of other globus pallidus neurons.
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Affiliation(s)
- Matthew H Higgs
- Department of Biology, The University of Texas at San Antonio, San Antonio, Texas
| | - James A Jones
- Department of Biology, The University of Texas at San Antonio, San Antonio, Texas
| | - C Savio Chan
- Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Charles J Wilson
- Department of Biology, The University of Texas at San Antonio, San Antonio, Texas
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10
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Phillips RS, Rosner I, Gittis AH, Rubin JE. The effects of chloride dynamics on substantia nigra pars reticulata responses to pallidal and striatal inputs. eLife 2020; 9:e55592. [PMID: 32894224 PMCID: PMC7476764 DOI: 10.7554/elife.55592] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 08/14/2020] [Indexed: 11/20/2022] Open
Abstract
As a rodent basal ganglia (BG) output nucleus, the substantia nigra pars reticulata (SNr) is well positioned to impact behavior. SNr neurons receive GABAergic inputs from the striatum (direct pathway) and globus pallidus (GPe, indirect pathway). Dominant theories of action selection rely on these pathways' inhibitory actions. Yet, experimental results on SNr responses to these inputs are limited and include excitatory effects. Our study combines experimental and computational work to characterize, explain, and make predictions about these pathways. We observe diverse SNr responses to stimulation of SNr-projecting striatal and GPe neurons, including biphasic and excitatory effects, which our modeling shows can be explained by intracellular chloride processing. Our work predicts that ongoing GPe activity could tune the SNr operating mode, including its responses in decision-making scenarios, and GPe output may modulate synchrony and low-frequency oscillations of SNr neurons, which we confirm using optogenetic stimulation of GPe terminals within the SNr.
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Affiliation(s)
- Ryan S Phillips
- Department of Mathematics, University of PittsburghPittsburghUnited States
- Center for the Neural Basis of CognitionPittsburghUnited States
| | - Ian Rosner
- Center for the Neural Basis of CognitionPittsburghUnited States
- Department of Biological Sciences, Carnegie Mellon UniversityPittsburghUnited States
| | - Aryn H Gittis
- Center for the Neural Basis of CognitionPittsburghUnited States
- Department of Biological Sciences, Carnegie Mellon UniversityPittsburghUnited States
| | - Jonathan E Rubin
- Department of Mathematics, University of PittsburghPittsburghUnited States
- Center for the Neural Basis of CognitionPittsburghUnited States
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11
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Morales JC, Higgs MH, Song SC, Wilson CJ. Broadband Entrainment of Striatal Low-Threshold Spike Interneurons. Front Neural Circuits 2020; 14:36. [PMID: 32655378 PMCID: PMC7326000 DOI: 10.3389/fncir.2020.00036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 05/19/2020] [Indexed: 11/13/2022] Open
Abstract
Striatal interneurons and spiny projection (SP) neurons are differentially tuned to spectral components of their input. Previous studies showed that spike responses of somatostatin/NPY-expressing low threshold spike (LTS) interneurons have broad frequency tuning, setting these cells apart from other striatal GABAergic interneurons and SP neurons. We investigated the mechanism of LTS interneuron spiking resonance and its relationship to non-spiking membrane impedance resonance, finding that abolition of impedance resonance did not alter spiking resonance. Because LTS interneurons are pacemakers whose rhythmic firing is perturbed by synaptic input, we tested the hypothesis that their spiking resonance arises from their phase resetting properties. Phase resetting curves (PRCs) were measured in LTS interneurons and SP neurons and used to make phase-oscillator models of both cell types. The models reproduced the broad tuning of LTS interneurons, and the differences from SP neurons. The spectral components of the PRC predicted each cell's sensitivity to corresponding input frequencies. LTS interneuron PRCs contain larger high-frequency components than SP neuron PRCs, providing enhanced responses to input frequencies above the cells' average firing rates. Thus, LTS cells can be entrained by input oscillations to which SP neurons are less responsive. These findings suggest that feedforward inhibition by LTS interneurons may regulate SP neurons' entrainment by oscillatory afferents.
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Affiliation(s)
- Juan C Morales
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Matthew H Higgs
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, United States
| | - Soomin C Song
- Skirball Institute of Biomolecular Medicine and Neurosciences Institute, New York University School of Medicine, New York, NY, United States
| | - Charles J Wilson
- Department of Biology, University of Texas at San Antonio, San Antonio, TX, United States
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Simmons DV, Higgs MH, Lebby S, Wilson CJ. Indirect pathway control of firing rate and pattern in the substantia nigra pars reticulata. J Neurophysiol 2020; 123:800-814. [PMID: 31940230 DOI: 10.1152/jn.00678.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Unitary pallido-nigral synaptic currents were measured using optogenetic stimulation, which activated up to three unitary synaptic inputs to each substantia nigra pars reticulata (SNr) cell. Episodic barrages of synaptic conductances were generated based on in vivo firing patterns of globus pallidus pars externa (GPe) cells and applied to SNr cells using conductance clamp. Barrage inputs were compared to continuous step conductances with the same mean. Barrage inputs and steps both slowed SNr neuron firing and produced disinhibition responses seen in peristimulus histograms. Barrages were less effective than steps at producing inhibition and disinhibition responses. Barrages, but not steps, produced irregular firing during the inhibitory response. Phase models of SNr neurons were constructed from their phase-resetting curves. The phase models reproduced the inhibition and disinhibition responses to the same inputs applied to the neurons. The disinhibition response did not require rebound currents but arose from reset of the cells' oscillation. The differences in firing rate and irregularity in response to barrage and step inhibition resulted from the high sensitivity of SNr neurons to inhibition at late phases in their intrinsic oscillation. During step inhibition, cells continued rhythmic firing at a reduced rate. During barrages, brief bouts of intense inhibition stalled the cells' phase evolution late in their cycle, close to firing, and even very brief respites from inhibition rapidly released single action potentials. The SNr cell firing pattern reflected the fine structure of the synaptic barrage from GPe, as well as its onset and offset.NEW & NOTEWORTHY The pallido-nigral pathway connects the striatum to spontaneously active basal ganglia output neurons in the substantia nigra. Each substantia nigra neuron receives powerful inhibitory synaptic connections from a small group of globus pallidus cells and may fire during pauses in pallidal activity. Despite lacking any hyperpolarization-activated rebound currents, they fire quickly to even brief pauses in the pallido-nigral inhibition. The mechanism of their rapid disinhibitory response is explained by features of their phase-resetting curves.
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Affiliation(s)
- DeNard V Simmons
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas
| | - Matthew H Higgs
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas
| | - Sharmon Lebby
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas
| | - Charles J Wilson
- Department of Biology, University of Texas at San Antonio, San Antonio, Texas
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