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Chen M, Chen Z, Xiao X, Zhou L, Fu R, Jiang X, Pang M, Xia J. Corticospinal circuit neuroplasticity may involve silent synapses: Implications for functional recovery facilitated by neuromodulation after spinal cord injury. IBRO Neurosci Rep 2022; 14:185-194. [PMID: 36824667 PMCID: PMC9941655 DOI: 10.1016/j.ibneur.2022.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Accepted: 08/15/2022] [Indexed: 10/15/2022] Open
Abstract
Spinal cord injury (SCI) leads to devastating physical consequences, such as severe sensorimotor dysfunction even lifetime disability, by damaging the corticospinal system. The conventional opinion that SCI is intractable due to the poor regeneration of neurons in the adult central nervous system (CNS) needs to be revisited as the CNS is capable of considerable plasticity, which underlie recovery from neural injury. Substantial spontaneous neuroplasticity has been demonstrated in the corticospinal motor circuitry following SCI. Some of these plastic changes appear to be beneficial while others are detrimental toward locomotor function recovery after SCI. The beneficial corticospinal plasticity in the spared corticospinal circuits can be harnessed therapeutically by multiple contemporary neuromodulatory approaches, especially the electrical stimulation-based modalities, in an activity-dependent manner to improve functional outcomes in post-SCI rehabilitation. Silent synapse generation and unsilencing contribute to profound neuroplasticity that is implicated in a variety of neurological disorders, thus they may be involved in the corticospinal motor circuit neuroplasticity following SCI. Exploring the underlying mechanisms of silent synapse-mediated neuroplasticity in the corticospinal motor circuitry that may be exploited by neuromodulation will inform a novel direction for optimizing therapeutic repair strategies and rehabilitative interventions in SCI patients.
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Key Words
- AMPARs, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors
- BDNF, brain-derived neurotrophic factor
- BMIs, brain-machine interfaces
- CPG, central pattern generator
- CST, corticospinal tract
- Corticospinal motor circuitry
- DBS, deep brain stimulation
- ESS, epidural spinal stimulation
- MEPs, motor-evoked potentials
- NHPs, non-human primates
- NMDARs, N-methyl-d-aspartate receptors
- Neuromodulation
- Neuroplasticity
- PSNs, propriospinal neurons
- Rehabilitation
- SCI, spinal cord injury
- STDP, spike timing-dependent plasticity
- Silent synapses
- Spinal cord injury
- TBS, theta burst stimulation
- TMS, transcranial magnetic stimulation
- TrkB, tropomyosin-related kinase B
- cTBS, continuous TBS
- iTBS, intermittent TBS
- mTOR, mammalian target of rapamycin
- rTMS, repetitive TMS
- tDCS, transcranial direct current stimulation
- tcSCS, transcutaneous spinal cord stimulation
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Affiliation(s)
- Mingcong Chen
- Department of Orthopedics and Traumatology, Shenzhen University General Hospital, Shenzhen, Guangdong 518055, China
| | - Zuxin Chen
- Shenzhen Key Laboratory of Drug Addiction, Shenzhen Neher Neural Plasticity Laboratory, the Brain Cognition and Brain Disease Institute, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences (CAS); Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China
| | - Xiao Xiao
- Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, Ministry of Education; Behavioral and Cognitive Neuroscience Center, Institute of Science and Technology for Brain-Inspired Intelligence; MOE Frontiers Center for Brain Science, Fudan University, Shanghai 200433, China
| | - Libing Zhou
- Guangdong-Hongkong-Macau CNS Regeneration Institute of Jinan University, Key Laboratory of CNS Regeneration (Jinan University)-Ministry of Education, Guangzhou, Guangdong 510632, China
| | - Rao Fu
- Department of Anatomy, School of Medicine, Sun Yat-sen University, Shenzhen, Guangdong 518100, China
| | - Xian Jiang
- Institute of Neurological and Psychiatric Disorder, Shenzhen Bay laboratory, Shenzhen, Guangdong 518000, China
| | - Mao Pang
- Department of Spine Surgery, the Third Affiliated Hospital of Sun Yat-sen University, Guangdong Provincial Center for Engineering and Technology Research of Minimally Invasive Spine Surgery, Guangzhou, Guangdong 510630, China
| | - Jianxun Xia
- Department of Basic Medical Sciences, Yunkang School of Medicine and Health, Nanfang College, Guangzhou, Guangdong 510970, China,Corresponding author.
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Abstract
The neurotransmitter gamma-aminobutyric acid (GABA) is widely distributed in the mammalian central nervous system, where it acts as a major mediator of synaptic inhibition. GABA also serves as a neurotransmitter in a range of invertebrate phyla, including arthropods, echinoderms, annelids, nematodes, and platyhelminthes. This article reviews evidence supporting the neurotransmitter role of GABA in gastropod molluscs, with an emphasis on its presence in identified neurons and well-characterized neural circuits. The collective findings indicate that GABAergic signaling participates in the selection and specification of motor programs, as well as the bilateral coordination of motor circuits. While relatively few in number, GABAergic neurons can influence neural circuits via inhibitory, excitatory, and modulatory synaptic actions. GABA's colocalization with peptidergic and classical neurotransmitters can broaden its integrative capacity. The functional properties of GABAergic neurons in simpler gastropod systems may provide insight into the role of this neurotransmitter phenotype in more complex brains.
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Key Words
- BCI, buccal-cerebral interneuron
- CBC, cerebral-buccal connective
- CBI, cerebral-buccal interneuron
- CNS, central nervous system
- CPG, central pattern generator
- Cr-Aint, cerebral A interneuron
- DA, dopamine
- EPSP, excitatory postsynaptic potential
- FCAP, feeding circuit activating peptide
- GABA, gamma-aminobutyric acid
- GABAli, GABA-like immunoreactivity
- IPSP, inhibitory postsynaptic potential
- PKC, protein kinase C
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Affiliation(s)
- MARK W. MILLER
- Institute of Neurobiology and Department of Anatomy and Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico 00901
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Abstract
When applied individually, thermal stress (1 hour at 30 °C) and (-)epicatechin (a flavonol found in green tea, e.g.) each enhance long-term memory formation following operant conditioning of Lymnaea aerial respiratory behavior. Snails demonstrate enhanced long-term memory formation when trained in epicatechin-treated pond water or when placed in 30 °C pond water for 1 hour, 1 hour prior to training in pond water. We ask here whether the combined application of epicatechin + thermal stress enhances long-term memory retention length beyond the maximal lengths of the individual factors alone. We report that the applied combination of epicatechin + thermal stress has a synergistic memory-enhancing effect; that is, when the two are applied in combination, memory persists longer than when either is applied alone. We then ask whether quercetin, a heat shock protein blocker, will affect the memory enhancement produced by the combined treatment of thermal stress and epicatechin. We report that quercetin does not decrease the memory enhancement of epicatechin, but it does decrease the memory enhancement by thermal stress; and it also decreases the memory persistence of snails exposed to both treatments in combination.
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