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Miralles RM, Boscia AR, Kittur S, Vundela SR, Wengert ER, Patel MK. Parvalbumin Interneuron Impairment Leads to Synaptic Transmission Deficits and Seizures in SCN8A Epileptic Encephalopathy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.09.579511. [PMID: 38464208 PMCID: PMC10925130 DOI: 10.1101/2024.02.09.579511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
SCN8A epileptic encephalopathy (EE) is a severe epilepsy syndrome resulting from de novo mutations in the voltage-gated sodium channel Na v 1.6, encoded by the gene SCN8A . Na v 1.6 is expressed in both excitatory and inhibitory neurons, yet previous studies have primarily focused on the impact SCN8A mutations have on excitatory neuron function, with limited studies on the importance of inhibitory interneurons to seizure onset and progression. Inhibitory interneurons are critical in balancing network excitability and are known to contribute to the pathophysiology of other epilepsies. Parvalbumin (PV) interneurons are the most prominent inhibitory neuron subtype in the brain, making up about 40% of inhibitory interneurons. Notably, PV interneurons express high levels of Na v 1.6. To assess the role of PV interneurons within SCN8A EE, we used two mouse models harboring patient-derived SCN8A gain-of-function mutations, Scn8a D/+ , where the SCN8A mutation N1768D is expressed globally, and Scn8a W/+ -PV, where the SCN8A mutation R1872W is selectively expressed in PV interneurons. Expression of the R1872W SCN8A mutation selectively in PV interneurons led to the development of spontaneous seizures in Scn8a W/+ -PV mice and seizure-induced death, decreasing survival compared to wild-type. Electrophysiology studies showed that PV interneurons in Scn8a D/+ and Scn8a W/+ -PV mice were susceptible to depolarization block, a state of action potential failure. Scn8a D/+ and Scn8a W/+ -PV interneurons also exhibited increased persistent sodium current, a hallmark of SCN8A gain-of-function mutations that contributes to depolarization block. Evaluation of synaptic connections between PV interneurons and pyramidal cells showed an increase in synaptic transmission failure at high frequencies (80-120Hz) as well as an increase in synaptic latency in Scn8a D/+ and Scn8a W/+ -PV interneurons. These data indicate a distinct impairment of synaptic transmission in SCN8A EE, potentially decreasing overall cortical network inhibition. Together, our novel findings indicate that failure of PV interneuron spiking via depolarization block along with frequency-dependent inhibitory synaptic impairment likely elicits an overall reduction in the inhibitory drive in SCN8A EE, leading to unchecked excitation and ultimately resulting in seizures and seizure-induced death.
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Guo W, Liu K, Wang Y, Ge X, Ma Y, Qin J, Zhang C, Zhao Y, Shi C. Neurotrophins and neural stem cells in posttraumatic brain injury repair. Animal Model Exp Med 2024; 7:12-23. [PMID: 38018458 PMCID: PMC10961886 DOI: 10.1002/ame2.12363] [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: 06/26/2023] [Accepted: 10/26/2023] [Indexed: 11/30/2023] Open
Abstract
Traumatic brain injury (TBI) is the main cause of disability, mental health disorder, and even death, with its incidence and social costs rising steadily. Although different treatment strategies have been developed and tested to mitigate neurological decline, a definitive cure for these conditions remains elusive. Studies have revealed that various neurotrophins represented by the brain-derived neurotrophic factor are the key regulators of neuroinflammation, apoptosis, blood-brain barrier permeability, neurite regeneration, and memory function. These factors are instrumental in alleviating neuroinflammation and promoting neuroregeneration. In addition, neural stem cells (NSC) contribute to nerve repair through inherent neuroprotective and immunomodulatory properties, the release of neurotrophins, the activation of endogenous NSCs, and intercellular signaling. Notably, innovative research proposals are emerging to combine BDNF and NSCs, enabling them to synergistically complement and promote each other in facilitating injury repair and improving neuron differentiation after TBI. In this review, we summarize the mechanism of neurotrophins in promoting neurogenesis and restoring neural function after TBI, comprehensively explore the potential therapeutic effects of various neurotrophins in basic research on TBI, and investigate their interaction with NSCs. This endeavor aims to provide a valuable insight into the clinical treatment and transformation of neurotrophins in TBI, thereby promoting the progress of TBI therapeutics.
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Affiliation(s)
- Wenwen Guo
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
- Gansu University of Traditional Chinese MedicineLanzhouP.R. China
| | - Ke Liu
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
- Gansu University of Traditional Chinese MedicineLanzhouP.R. China
| | - Yinghua Wang
- Medical College of Yan'an UniversityYan'anP.R. China
| | - Xu Ge
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
| | - Yifan Ma
- Gansu University of Traditional Chinese MedicineLanzhouP.R. China
| | - Jing Qin
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
| | - Caiqin Zhang
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
| | - Ya Zhao
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
| | - Changhong Shi
- Laboratory Animal CenterFourth Military Medical UniversityXi'anP.R. China
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Perisomatic Inhibition and Its Relation to Epilepsy and to Synchrony Generation in the Human Neocortex. Int J Mol Sci 2021; 23:ijms23010202. [PMID: 35008628 PMCID: PMC8745731 DOI: 10.3390/ijms23010202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 12/21/2021] [Accepted: 12/22/2021] [Indexed: 11/21/2022] Open
Abstract
Inhibitory neurons innervating the perisomatic region of cortical excitatory principal cells are known to control the emergence of several physiological and pathological synchronous events, including epileptic interictal spikes. In humans, little is known about their role in synchrony generation, although their changes in epilepsy have been thoroughly investigated. This paper demonstraits how parvalbumin (PV)- and type 1 cannabinoid receptor (CB1R)-positive perisomatic interneurons innervate pyramidal cell bodies, and their role in synchronous population events spontaneously emerging in the human epileptic and non-epileptic neocortex, in vitro. Quantitative electron microscopy showed that the overall, PV+ and CB1R+ somatic inhibitory inputs remained unchanged in focal cortical epilepsy. On the contrary, the size of PV-stained synapses increased, and their number decreased in epileptic samples, in synchrony generating regions. Pharmacology demonstrated—in conjunction with the electron microscopy—that although both perisomatic cell types participate, PV+ cells have stronger influence on the generation of population activity in epileptic samples. The somatic inhibitory input of neocortical pyramidal cells remained almost intact in epilepsy, but the larger and consequently more efficient somatic synapses might account for a higher synchrony in this neuron population. This, together with epileptic hyperexcitability, might make a cortical region predisposed to generate or participate in hypersynchronous events.
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Gu F, Parada I, Yang T, Longo FM, Prince DA. Partial Activation of TrkB Receptors Corrects Interneuronal Calcium Channel Dysfunction and Reduces Epileptogenic Activity in Neocortex following Injury. Cereb Cortex 2020; 30:5180-5189. [PMID: 32488246 PMCID: PMC7391412 DOI: 10.1093/cercor/bhz254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 09/12/2019] [Accepted: 09/12/2019] [Indexed: 11/13/2022] Open
Abstract
Decreased GABAergic inhibition due to dysfunction of inhibitory interneurons plays an important role in post-traumatic epileptogenesis. Reduced N-current Ca2+ channel function in GABAergic terminals contributes to interneuronal abnormalities and neural circuit hyperexcitability in the partial neocortical isolation (undercut, UC) model of post-traumatic epileptogenesis. Because brain-derived neurotrophic factor (BDNF) supports the development and maintenance of interneurons, we hypothesized that the activation of BDNF tropomyosin kinase B (TrkB) receptors by a small molecule, TrkB partial agonist, PTX BD4-3 (BD), would correct N channel abnormalities and enhance inhibitory synaptic transmission in UC cortex. Immunocytochemistry (ICC) and western blots were used to quantify N- and P/Q-type channels. We recorded evoked (e)IPSCs and responses to N and P/Q channel blockers to determine the effects of BD on channel function. Field potential recordings were used to determine the effects of BD on circuit hyperexcitability. Chronic BD treatment 1) upregulated N and P/Q channel immunoreactivity in GABAergic terminals; 2) increased the effects of N or P/Q channel blockade on evoked inhibitory postsynaptic currents (eIPSCs); 3) increased GABA release probability and the frequency of sIPSCs; and 4) reduced the incidence of epileptiform discharges in UC cortex. The results suggest that chronic TrkB activation is a promising approach for rescuing injury-induced calcium channel abnormalities in inhibitory terminals, thereby improving interneuronal function and suppressing circuit hyperexcitability.
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Affiliation(s)
- Feng Gu
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5122, USA
| | - Isabel Parada
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5122, USA
| | - Tao Yang
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5122, USA
| | - Frank M Longo
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5122, USA
| | - David A Prince
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305-5122, USA
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Takahashi DK, Jin S, Prince DA. Gabapentin Prevents Progressive Increases in Excitatory Connectivity and Epileptogenesis Following Neocortical Trauma. Cereb Cortex 2018; 28:2725-2740. [PMID: 28981586 PMCID: PMC6041890 DOI: 10.1093/cercor/bhx152] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 05/30/2017] [Accepted: 06/01/2017] [Indexed: 11/12/2022] Open
Abstract
Neocortical injury initiates a cascade of events, some of which result in maladaptive epileptogenic reorganization of surviving neural circuits. Research focused on molecular and organizational changes that occur following trauma may reveal processes that underlie human post-traumatic epilepsy (PTE), a common and unfortunate consequence of traumatic brain injury. The latency between injury and development of PTE provides an opportunity for prophylactic intervention, once the key underlying mechanisms are understood. In rodent neocortex, injury to pyramidal neurons promotes axonal sprouting, resulting in increased excitatory circuitry that is one important factor promoting epileptogenesis. We used laser-scanning photostimulation of caged glutamate and whole-cell recordings in in vitro slices from injured neocortex to assess formation of new excitatory synapses, a process known to rely on astrocyte-secreted thrombospondins (TSPs), and to map the distribution of maladaptive circuit reorganization. We show that this reorganization is centered principally in layer V and associated with development of epileptiform activity. Short-term blockade of the synaptogenic effects of astrocyte-secreted TSPs with gabapentin (GBP) after injury suppresses the new excitatory connectivity and epileptogenesis for at least 2 weeks. Results reveal that aberrant circuit rewiring is progressive in vivo and provide further rationale for prophylactic anti-epileptogenic use of gabapentinoids following cortical trauma.
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Affiliation(s)
- D K Takahashi
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - Sha Jin
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
| | - D A Prince
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, USA
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Nichols J, Bjorklund GR, Newbern J, Anderson T. Parvalbumin fast-spiking interneurons are selectively altered by paediatric traumatic brain injury. J Physiol 2018; 596:1277-1293. [PMID: 29333742 PMCID: PMC5878227 DOI: 10.1113/jp275393] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 12/19/2017] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Traumatic brain injury (TBI) in children remains a leading cause of death and disability and it remains poorly understood why children have worse outcomes and longer recover times. TBI has shown to alter cortical excitability and inhibitory drive onto excitatory neurons, yet few studies have directly examined changes to cortical interneurons. This is addressed in the present study using a clinically relevant model of severe TBI (controlled cortical impact) in interneuron cell type specific Cre-dependent mice. Mice subjected to controlled cortical impact exhibit specific loss of parvalbumin (PV) but not somatostatin immunoreactivity and cell density in the peri-injury zone. PV interneurons are primarily of a fast-spiking (FS) phenotype that persisted in the peri-injury zone but received less frequent inhibitory and stronger excitatory post-synaptic currents. The targeted loss of PV-FS interneurons appears to be distinct from previous reports in adult mice suggesting that TBI-induced pathophysiology is dependent on the age at time of impact. ABSTRACT Paediatric traumatic brain injury (TBI) is a leading cause of death and disability in children. Traditionally, ongoing neurodevelopment and neuroplasticity have been considered to confer children with an advantage following TBI. However, recent findings indicate that the paediatric brain may be more sensitive to brain injury. Inhibitory interneurons are essential for proper cortical function and are implicated in the pathophysiology of TBI, yet few studies have directly investigated TBI-induced changes to interneurons themselves. Accordingly, in the present study, we examine how inhibitory neurons are altered following controlled cortical impact (CCI) in juvenile mice with targeted Cre-dependent fluorescence labelling of interneurons (Vgat:Cre/Ai9 and PV:Cre/Ai6). Although CCI failed to alter the number of excitatory neurons or somatostatin-expressing interneurons in the peri-injury zone, it significantly decreased the density of parvalbumin (PV) immunoreactive cells by 71%. However, PV:Cre/Ai6 mice subjected to CCI showed a lower extent of fluorescence labelled cell loss. PV interneurons are predominantly of a fast-spiking (FS) phenotype and, when recorded electrophysiologically from the peri-injury zone, exhibited intrinsic properties similar to those of control neurons. Synaptically, CCI induced a decrease in inhibitory drive onto FS interneurons combined with an increase in the strength of excitatory events. The results of the present study indicate that CCI induced both a loss of PV interneurons and an even greater loss of PV expression. This suggests caution is required when interpreting changes in PV immunoreactivity alone as direct evidence of interneuronal loss. Furthermore, in contrast to reports in adults, TBI in the paediatric brain selectively alters PV-FS interneurons, primarily resulting in a loss of interneuronal inhibition.
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Affiliation(s)
- Joshua Nichols
- University of ArizonaCollege of Medicine – PhoenixPhoenixAZUSA
- School of Life SciencesArizona State UniversityAZUSA
| | | | - Jason Newbern
- School of Life SciencesArizona State UniversityAZUSA
| | - Trent Anderson
- University of ArizonaCollege of Medicine – PhoenixPhoenixAZUSA
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Gu F, Parada I, Yang T, Longo FM, Prince DA. Partial TrkB receptor activation suppresses cortical epileptogenesis through actions on parvalbumin interneurons. Neurobiol Dis 2018; 113:45-58. [PMID: 29408225 DOI: 10.1016/j.nbd.2018.01.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 01/21/2018] [Accepted: 01/24/2018] [Indexed: 01/17/2023] Open
Abstract
Post-traumatic epilepsy is one of the most common and difficult to treat forms of acquired epilepsy worldwide. Currently, there is no effective way to prevent post-traumatic epileptogenesis. It is known that abnormalities of interneurons, particularly parvalbumin-containing interneurons, play a critical role in epileptogenesis following traumatic brain injury. Thus, enhancing the function of existing parvalbumin interneurons might provide a logical therapeutic approach to prevention of post-traumatic epilepsy. The known positive effects of brain-derived neurotrophic factor on interneuronal growth and function through activation of its receptor tropomyosin receptor kinase B, and its decrease after traumatic brain injury, led us to hypothesize that enhancing trophic support might improve parvalbumin interneuronal function and decrease epileptogenesis. To test this hypothesis, we used the partial neocortical isolation ('undercut', UC) model of posttraumatic epileptogenesis in mature rats that were treated for 2 weeks, beginning on the day of injury, with LM22A-4, a newly designed partial agonist at the tropomyosin receptor kinase B. Effects of treatment were assessed with Western blots to measure pAKT/AKT; immunocytochemistry and whole cell patch clamp recordings to examine functional and structural properties of GABAergic interneurons; field potential recordings of epileptiform discharges in vitro; and video-EEG recordings of PTZ-induced seizures in vivo. Results showed that LM22A-4 treatment 1) increased pyramidal cell perisomatic immunoreactivity for VGAT, GAD65 and parvalbumin; 2) increased the density of close appositions of VGAT/gephyrin immunoreactive puncta (putative inhibitory synapses) on pyramidal cell somata; 3) increased the frequency of mIPSCs in pyramidal cells; and 4) decreased the incidence of spontaneous and evoked epileptiform discharges in vitro. 5) Treatment of rats with PTX BD4-3, another partial TrkB receptor agonist, reduced the incidence of bicuculline-induced ictal episodes in vitro and PTZ induced electrographic and behavioral ictal episodes in vivo. 6) Inactivation of TrkB receptors in undercut TrkBF616A mice with 1NMPP1 abolished both LM22A-4-induced effects on mIPSCs and on increased perisomatic VGAT-IR. Results indicate that chronic activation of the tropomyosin receptor kinase B by a partial agonist after cortical injury can enhance structural and functional measures of GABAergic inhibition and suppress posttraumatic epileptogenesis. Although the full agonist effects of brain-derived neurotrophic factor and tropomyosin receptor kinase B activation in epilepsy models have been controversial, the present results indicate that such trophic activation by a partial agonist may potentially serve as an effective therapeutic option for prophylactic treatment of posttraumatic epileptogenesis, and treatment of other neurological and psychiatric disorders whose pathogenesis involves impaired parvalbumin interneuronal function.
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Affiliation(s)
- Feng Gu
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States
| | - Isabel Parada
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States
| | - Tao Yang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States
| | - Frank M Longo
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States
| | - David A Prince
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, United States.
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Kang JQ. Defects at the crossroads of GABAergic signaling in generalized genetic epilepsies. Epilepsy Res 2017; 137:9-18. [PMID: 28865303 DOI: 10.1016/j.eplepsyres.2017.08.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Revised: 08/14/2017] [Accepted: 08/22/2017] [Indexed: 12/16/2022]
Abstract
Seizure disorders are very common and affect 3% of the general population. The recurrent unprovoked seizures that are also called epilepsies are highly diverse as to both underlying genetic basis and clinic presentations. Recent genetic advances and sequencing technologies indicate that many epilepsies previously thought to be without known causes, or idiopathic generalized epilepsies (IGEs), are virtually genetic epilepsy as they are caused by genetic variations. IGEs are estimated to account for ∼15-20% of all epilepsies. Initially IGEs were primarily considered channelopathies, because the first genetic defects identified in IGEs involved ion channel genes. However, new findings indicate that mutations in many non ion channel genes are also involved in addition to those in ion channel genes. Interestingly, mutations in many genes associated with epilepsy affect GABAergic signaling, a major biological pathway in epilepsy. Additionally, many antiepileptic drugs work via enhancing GABAergic signaling. Hence, the review will focus on the mutations that impair GABAergic signaling and selectively discuss the newly identified STXBP1, PRRT2, and DNM1 in addition to those long-established epilepsy ion channel genes that also impair GABAergic signaling like SCN1A and GABAA receptor subunit genes. GABAergic signaling includes the pre- and post- synaptic mechanisms. Some mutations, such as STXBP1, PRRT2, DNM1, and SCN1A, impair GABAergic signaling mainly via pre-synaptic mechanisms while those mutations in GABAA receptor subunit genes impair GABAergic signaling via post-synaptic mechanisms. Nevertheless, these findings suggest impaired GABAergic signaling is a converging pathway of defects for many ion channel or non ion channel mutations associated with genetic epilepsies.
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Affiliation(s)
- Jing-Qiong Kang
- Departments of Neurology, Vanderbilt University Medical Center, Nashville, TN, 37232-8552, USA; Affiliated Hospital of Nantong University, Jiangsu, 226001, China; Vanderbilt Brain Institute, Vanderbilt Kennedy Center of Human Development, Vanderbilt University, Nashville, TN, 37232-8522, USA.
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Gu F, Parada I, Shen F, Li J, Bacci A, Graber K, Taghavi RM, Scalise K, Schwartzkroin P, Wenzel J, Prince DA. Structural alterations in fast-spiking GABAergic interneurons in a model of posttraumatic neocortical epileptogenesis. Neurobiol Dis 2017; 108:100-114. [PMID: 28823934 DOI: 10.1016/j.nbd.2017.08.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 08/11/2017] [Accepted: 08/16/2017] [Indexed: 01/22/2023] Open
Abstract
Electrophysiological experiments in the partial cortical isolation ("undercut" or "UC") model of injury-induced neocortical epileptogenesis have shown alterations in GABAergic synaptic transmission attributable to abnormalities in presynaptic terminals. To determine whether the decreased inhibition was associated with structural abnormalities in GABAergic interneurons, we used immunocytochemical techniques, confocal microscopy and EM in UC and control sensorimotor rat cortex to analyze structural alterations in fast-spiking parvalbumin-containing interneurons and pyramidal (Pyr) cells of layer V. Principle findings were: 1) there were no decreases in counts of parvalbumin (PV)- or GABA-immunoreactive interneurons in UC cortex, however there were significant reductions in expression of VGAT and GAD-65 and -67 in halos of GABAergic terminals around Pyr somata in layer V. 2) Consistent with previous results, somatic size and density of Pyr cells was decreased in infragranular layers of UC cortex. 3) Dendrites of biocytin-filled FS interneurons were significantly decreased in volume. 4) There were decreases in the size and VGAT content of GABAergic boutons in axons of biocytin-filled FS cells in the UC, together with a decrease in colocalization with postsynaptic gephyrin, suggesting a reduction in GABAergic synapses. Quantitative EM of layer V Pyr somata confirmed the reduction in inhibitory synapses. 5) There were marked and lasting reductions in brain derived neurotrophic factor (BDNF)-IR and -mRNA in Pyr cells and decreased TrkB-IR on PV cells in UC cortex. 6) Results lead to the hypothesis that reduction in trophic support by BDNF derived from Pyr cells may contribute to the regressive changes in axonal terminals and dendrites of FS cells in the UC cortex and decreased GABAergic inhibition. SIGNIFICANCE Injury to cortical structures is a major cause of epilepsy, accounting for about 20% of cases in the general population, with an incidence as high as ~50% among brain-injured personnel in wartime. Loss of GABAergic inhibitory interneurons is a significant pathophysiological factor associated with epileptogenesis following brain trauma and other etiologies. Results of these experiments show that the largest population of cortical interneurons, the parvalbumin-containing fast-spiking (FS) interneurons, are preserved in the partial neocortical isolation model of partial epilepsy. However, axonal terminals of these cells are structurally abnormal, have decreased content of GABA synthetic enzymes and vesicular GABA transporter and make fewer synapses onto pyramidal neurons. These structural abnormalities underlie defects in GABAergic neurotransmission that are a key pathophysiological factor in epileptogenesis found in electrophysiological experiments. BDNF, and its TrkB receptor, key factors for maintenance of interneurons and pyramidal neurons, are decreased in the injured cortex. Results suggest that supplying BDNF to the injured epileptogenic brain may reverse the structural and functional abnormalities in the parvalbumin FS interneurons and provide an antiepileptogenic therapy.
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Affiliation(s)
- Feng Gu
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Isabel Parada
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Fran Shen
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Judith Li
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Alberto Bacci
- ICM - Hôpital Pitié Salpêtrière, 7, bd de l'hôpital, 75013 Paris, France
| | - Kevin Graber
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Reza Moein Taghavi
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Karina Scalise
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States
| | - Philip Schwartzkroin
- Department of Neurological Surgery, University of California, Davis, United States
| | - Jurgen Wenzel
- Department of Neurological Surgery, University of California, Davis, United States
| | - David A Prince
- Epilepsy Research Laboratories, Stanford Univ. Sch. of Medicine, United States.
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Kim SY, Senatorov VV, Morrissey CS, Lippmann K, Vazquez O, Milikovsky DZ, Gu F, Parada I, Prince DA, Becker AJ, Heinemann U, Friedman A, Kaufer D. TGFβ signaling is associated with changes in inflammatory gene expression and perineuronal net degradation around inhibitory neurons following various neurological insults. Sci Rep 2017; 7:7711. [PMID: 28794441 PMCID: PMC5550510 DOI: 10.1038/s41598-017-07394-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 06/27/2017] [Indexed: 01/17/2023] Open
Abstract
Brain damage due to stroke or traumatic brain injury (TBI), both leading causes of serious long-term disability, often leads to the development of epilepsy. Patients who develop post-injury epilepsy tend to have poor functional outcomes. Emerging evidence highlights a potential role for blood-brain barrier (BBB) dysfunction in the development of post-injury epilepsy. However, common mechanisms underlying the pathological hyperexcitability are largely unknown. Here, we show that comparative transcriptome analyses predict remodeling of extracellular matrix (ECM) as a common response to different types of injuries. ECM-related transcriptional changes were induced by the serum protein albumin via TGFβ signaling in primary astrocytes. In accordance with transcriptional responses, we found persistent degradation of protective ECM structures called perineuronal nets (PNNs) around fast-spiking inhibitory interneurons, in a rat model of TBI as well as in brains of human epileptic patients. Exposure of a naïve brain to albumin was sufficient to induce the transcriptional and translational upregulation of molecules related to ECM remodeling and the persistent breakdown of PNNs around fast-spiking inhibitory interneurons, which was contingent on TGFβ signaling activation. Our findings provide insights on how albumin extravasation that occurs upon BBB dysfunction in various brain injuries can predispose neural circuitry to the development of chronic inhibition deficits.
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Affiliation(s)
- Soo Young Kim
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
| | - Vladimir V Senatorov
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Christapher S Morrissey
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Kristina Lippmann
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, D10117, Germany.,Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig, 04315, Germany
| | - Oscar Vazquez
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Dan Z Milikovsky
- Departments of Cognitive and Brain Sciences, Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
| | - Feng Gu
- Department of Neurology and Neurological Sciences, , Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Isabel Parada
- Department of Neurology and Neurological Sciences, , Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - David A Prince
- Department of Neurology and Neurological Sciences, , Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Albert J Becker
- Department of Neuropathology, University of Bonn Medical Center, Bonn, 53105, Germany
| | - Uwe Heinemann
- Institute of Neurophysiology, Charité Universitätsmedizin Berlin, Berlin, D10117, Germany
| | - Alon Friedman
- Departments of Cognitive and Brain Sciences, Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel.,Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Daniela Kaufer
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, 94720, USA. .,Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA. .,Canadian Institute for Advanced Research (CIFAR) Program in Child and Brain Development, ON M5G 1Z8, Toronto, Canada.
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11
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Faria LC, Gu F, Parada I, Barres B, Luo ZD, Prince DA. Epileptiform activity and behavioral arrests in mice overexpressing the calcium channel subunit α2δ-1. Neurobiol Dis 2017; 102:70-80. [PMID: 28193459 DOI: 10.1016/j.nbd.2017.01.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/17/2017] [Accepted: 01/25/2017] [Indexed: 10/20/2022] Open
Abstract
The alpha2delta-1 subunit (α2δ-1) of voltage-gated calcium channels is a receptor for astrocyte-secreted thrombospondins that promote developmental synaptogenesis. Alpha2delta-1 receptors are upregulated in models of injury-induced peripheral pain and epileptogenic neocortical trauma associated with an enhancement of excitatory synaptic connectivity. These results lead to the hypothesis that overexpression of α2δ-1 alone in neocortex of uninjured transgenic (TG) mice might result in increased excitatory connectivity and consequent cortical hyperexcitability and epileptiform activity. Whole cell recordings from layer V pyramidal neurons in somatosensory cortical slices of TG mice showed increased frequency and amplitude of miniature and spontaneous EPSCs and prolonged bursts of polysynaptic EPSCs. Epileptiform field potentials were evoked in layers II/III and V of brain slices from TG mice, but not controls. Dual immunoreactivity for Vglut-2 and PSD95 showed increased density of close appositions in TG mice compared to controls, suggesting an increased number of excitatory synapses. Video-EEG monitoring showed that 13/13 implanted TG mice aged >P21, but not controls, had frequent abnormal spontaneous epileptiform events, consisting of variable duration, high amplitude bi-hemispheric irregular bursts of delta activity, spikes and sharp waves lasting many seconds, with a variable peak frequency of ~1-3Hz, associated with behavioral arrest. The epileptiform EEG abnormalities and behavioral arrests were reversibly eliminated by treatment with i.p. ethosuximide. Behavioral seizures, consisting of ~15-30s duration episodes of rigid arched tail and head and body extension, followed by loss of balance and falling, frequently occurred in adult TG mice during recovery from isoflurane-induced anesthesia, but were rare in WT mice. Results show that over-expression of α2δ-1 subunits increases cortical excitatory connectivity and leads to neocortical hyperexcitability and epileptiform activity associated with behavioral arrests in adult TG mice. Similar increases in expression of α2δ-1 in models of cortical injury may play an important role in epileptogenesis. SIGNIFICANCE Binding of astrocytic-secreted thrombospondins to their α2δ-1 receptor facilitates excitatory synapse formation and excitatory transmission during cortical development and after injury. Upregulation of α2δ-1 is present in models of injury-induced pain and epileptogenic cortical trauma, along with many other molecular alterations. Here we show that overexpression of α2δ-1 alone in TG mice can enhance excitatory connectivity in neocortex and lead to neural circuit hyperexcitability and episodes of electrographic epileptiform activity, associated with behavioral arrests in transgenic mice. α2δ-1 is the high-affinity receptor for gabapentinoids and a potential target for prophylactic treatment of posttraumatic epilepsy and other disorders in which excessive aberrant excitatory connectivity is a pathophysiological feature.
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Affiliation(s)
- Leonardo C Faria
- Department of Neurology and Neurological Sciences, Stanford University, School of Medicine, Stanford, CA 94305, USA
| | - Feng Gu
- Department of Neurology and Neurological Sciences, Stanford University, School of Medicine, Stanford, CA 94305, USA
| | - Isabel Parada
- Department of Neurology and Neurological Sciences, Stanford University, School of Medicine, Stanford, CA 94305, USA
| | - Ben Barres
- Department of Neurobiology, Stanford University, Howard Hughes Medical Institute, Stanford School of Medicine, Stanford, CA 94305-5125, USA
| | - Z David Luo
- Department of Anesthesiology and Perioperative Care, Department of Pharmacology, University of California, Irvine Medical Center, Orange, CA 92868, USA
| | - David A Prince
- Department of Neurology and Neurological Sciences, Stanford University, School of Medicine, Stanford, CA 94305, USA.
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12
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David LS, Topolnik L. Target-specific alterations in the VIP inhibitory drive to hippocampal GABAergic cells after status epilepticus. Exp Neurol 2017; 292:102-112. [PMID: 28315308 DOI: 10.1016/j.expneurol.2017.03.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 03/08/2017] [Accepted: 03/14/2017] [Indexed: 01/09/2023]
Abstract
Status epilepticus (SE) is associated with complex reorganization of hippocampal circuits involving a significant loss of specific subtypes of GABAergic interneurons. While adaptive circuit plasticity may increase the chances for recruitment of surviving interneurons, the underlying mechanisms remain largely unknown. We studied the alterations in the inhibitory tone received by the hippocampal CA1 oriens/alveus (O/A) interneurons from the vasoactive intestinal peptide (VIP)- and calretinin (CR)-expressing interneurons using the pilocarpine-induced status epilepticus (SE) model of epilepsy. Our data showed that, while the overall density of the VIP/CR-co-expressing interneurons remained preserved, the number of axonal boutons made by these cells within the CA1 O/A was significantly lower after SE. Furthermore, VIP/CR interneurons exhibited significant alterations in their dendritic morphology and passive membrane properties. Subsequently, while all O/A interneuron types, including oriens-lacunosum moleculare (OLM), bistratified (Bis) and basket cells, exhibited decrease in spontaneous inhibitory drive, Bis and basket cells showed a smaller amplitude of light-evoked IPSCs mediated by the selective activation of VIP-positive interneurons. These data point to the target cell-specific changes in the inhibitory tone provided by the VIP cells to O/A interneurons following SE. Given that basket, Bis and OLM cells coordinate different subcellular domains of pyramidal neurons, significant disinhibition of basket and Bis cells along with a previously reported loss of the OLMs may result in a redistribution of inhibition converging onto pyramidal neurons, with a direct impact onto their recruitment to epileptiform network activity and seizure propagation.
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Affiliation(s)
- Linda Suzanne David
- Neuroscience Axis, CHU de Québec Research Center, Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada
| | - Lisa Topolnik
- Neuroscience Axis, CHU de Québec Research Center, Department of Biochemistry, Microbiology and Bio-informatics, Laval University, Québec, PQ, Canada.
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13
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Khaspekov LG, Frumkina LE. Molecular mechanisms mediating involvement of glial cells in brain plastic remodeling in epilepsy. BIOCHEMISTRY (MOSCOW) 2017; 82:380-391. [DOI: 10.1134/s0006297917030178] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Jiang X, Lachance M, Rossignol E. Involvement of cortical fast-spiking parvalbumin-positive basket cells in epilepsy. PROGRESS IN BRAIN RESEARCH 2016; 226:81-126. [PMID: 27323940 DOI: 10.1016/bs.pbr.2016.04.012] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABAergic interneurons of the parvalbumin-positive fast-spiking basket cells subtype (PV INs) are important regulators of cortical network excitability and of gamma oscillations, involved in signal processing and cognition. Impaired development or function of PV INs has been associated with epilepsy in various animal models of epilepsy, as well as in some genetic forms of epilepsy in humans. In this review, we provide an overview of some of the experimental data linking PV INs dysfunction with epilepsy, focusing on disorders of the specification, migration, maturation, synaptic function, or connectivity of PV INs. Furthermore, we reflect on the potential therapeutic use of cell-type specific stimulation of PV INs within active networks and on the transplantation of PV INs precursors in the treatment of epilepsy and its comorbidities.
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Affiliation(s)
- X Jiang
- Université de Montréal, Montréal, QC, Canada; CHU Ste-Justine Research Center, Montréal, QC, Canada
| | - M Lachance
- CHU Ste-Justine Research Center, Montréal, QC, Canada
| | - E Rossignol
- Université de Montréal, Montréal, QC, Canada; CHU Ste-Justine Research Center, Montréal, QC, Canada.
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15
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Kim SY, Porter BE, Friedman A, Kaufer D. A potential role for glia-derived extracellular matrix remodeling in postinjury epilepsy. J Neurosci Res 2016; 94:794-803. [PMID: 27265805 DOI: 10.1002/jnr.23758] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Revised: 04/07/2016] [Accepted: 04/07/2016] [Indexed: 01/04/2023]
Abstract
Head trauma and vascular injuries are known risk factors for acquired epilepsy. The sequence of events that lead from the initial injury to the development of epilepsy involves complex plastic changes and circuit rewiring. In-depth, comprehensive understanding of the epileptogenic process is critical for the identification of disease-modifying targets. Here we review the complex interactions of cellular and extracellular components that may promote epileptogenesis, with an emphasis on the role of astrocytes. Emerging evidence demonstrates that astrocytes promptly respond to brain damage and play a critical role in the development of postinjury epilepsy. Astrocytes have been shown to regulate extracellular matrix (ECM) remodeling, which can affect plasticity and stability of synapses and, in turn, contribute to the epileptogenic process. From these separate lines of evidence, we present a hypothesis suggesting a possible role for astrocyte-regulated remodeling of ECM and perineuronal nets, a specialized ECM structure around fast-spiking inhibitory interneurons, in the development and progression of posttraumatic epilepsies. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Soo Young Kim
- Department of Integrative Biology, University of California, Berkeley, Berkeley, California.,Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California
| | - Brenda E Porter
- Department of Neurology, Stanford University School of Medicine, Palo Alto, California
| | - Alon Friedman
- Departments of Physiology and Cell Biology, Cognitive and Brain Sciences, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Department of Medical Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Daniela Kaufer
- Department of Integrative Biology, University of California, Berkeley, Berkeley, California.,Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California.,Canadian Institute for Advanced Research Program in Child and Brain Development, Toronto, Ontario, Canada
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16
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Dulla CG, Coulter DA, Ziburkus J. From Molecular Circuit Dysfunction to Disease: Case Studies in Epilepsy, Traumatic Brain Injury, and Alzheimer's Disease. Neuroscientist 2016; 22:295-312. [PMID: 25948650 PMCID: PMC4641826 DOI: 10.1177/1073858415585108] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Complex circuitry with feed-forward and feed-back systems regulate neuronal activity throughout the brain. Cell biological, electrical, and neurotransmitter systems enable neural networks to process and drive the entire spectrum of cognitive, behavioral, and motor functions. Simultaneous orchestration of distinct cells and interconnected neural circuits relies on hundreds, if not thousands, of unique molecular interactions. Even single molecule dysfunctions can be disrupting to neural circuit activity, leading to neurological pathology. Here, we sample our current understanding of how molecular aberrations lead to disruptions in networks using three neurological pathologies as exemplars: epilepsy, traumatic brain injury (TBI), and Alzheimer's disease (AD). Epilepsy provides a window into how total destabilization of network balance can occur. TBI is an abrupt physical disruption that manifests in both acute and chronic neurological deficits. Last, in AD progressive cell loss leads to devastating cognitive consequences. Interestingly, all three of these neurological diseases are interrelated. The goal of this review, therefore, is to identify molecular changes that may lead to network dysfunction, elaborate on how altered network activity and circuit structure can contribute to neurological disease, and suggest common threads that may lie at the heart of molecular circuit dysfunction.
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Affiliation(s)
- Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, USA
| | - Douglas A Coulter
- Department of Pediatrics and Neuroscience, University of Pennsylvania Perleman School of Medicine, Philadelphia, PA, USA Division of Neurology and the Research Institute of Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Jokubas Ziburkus
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
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Buckmaster PS, Yamawaki R, Thind K. More Docked Vesicles and Larger Active Zones at Basket Cell-to-Granule Cell Synapses in a Rat Model of Temporal Lobe Epilepsy. J Neurosci 2016; 36:3295-308. [PMID: 26985038 PMCID: PMC4792940 DOI: 10.1523/jneurosci.4049-15.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/20/2016] [Accepted: 02/04/2016] [Indexed: 11/21/2022] Open
Abstract
Temporal lobe epilepsy is a common and challenging clinical problem, and its pathophysiological mechanisms remain unclear. One possibility is insufficient inhibition in the hippocampal formation where seizures tend to initiate. Normally, hippocampal basket cells provide strong and reliable synaptic inhibition at principal cell somata. In a rat model of temporal lobe epilepsy, basket cell-to-granule cell (BC→GC) synaptic transmission is more likely to fail, but the underlying cause is unknown. At some synapses, probability of release correlates with bouton size, active zone area, and number of docked vesicles. The present study tested the hypothesis that impaired GABAergic transmission at BC→GC synapses is attributable to ultrastructural changes. Boutons making axosomatic symmetric synapses in the granule cell layer were reconstructed from serial electron micrographs. BC→GC boutons were predicted to be smaller in volume, have fewer and smaller active zones, and contain fewer vesicles, including fewer docked vesicles. Results revealed the opposite. Compared with controls, epileptic pilocarpine-treated rats displayed boutons with over twice the average volume, active zone area, total vesicles, and docked vesicles and with more vesicles closer to active zones. Larger active zones in epileptic rats are consistent with previous reports of larger amplitude miniature IPSCs and larger BC→GC quantal size. Results of this study indicate that transmission failures at BC→GC synapses in epileptic pilocarpine-treated rats are not attributable to smaller boutons or fewer docked vesicles. Instead, processes following vesicle docking, including priming, Ca(2+) entry, or Ca(2+) coupling with exocytosis, might be responsible. SIGNIFICANCE STATEMENT One in 26 people develops epilepsy, and temporal lobe epilepsy is a common form. Up to one-third of patients are resistant to currently available treatments. This study tested a potential underlying mechanism for previously reported impaired inhibition in epileptic animals at basket cell-to-granule cell (BC→GC) synapses, which normally are reliable and strong. Electron microscopy was used to evaluate 3D ultrastructure of BC→GC synapses in a rat model of temporal lobe epilepsy. The hypothesis was that impaired synaptic transmission is attributable to smaller boutons, smaller synapses, and abnormally low numbers of synaptic vesicles. Results revealed the opposite. These findings suggest that impaired transmission at BC→GC synapses in epileptic rats is attributable to later steps in exocytosis following vesicle docking.
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Affiliation(s)
- Paul S Buckmaster
- Departments of Comparative Medicine and Neurology and Neurological Sciences, Stanford University, Stanford, California 94305
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18
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Takahashi DK, Gu F, Parada I, Vyas S, Prince DA. Aberrant excitatory rewiring of layer V pyramidal neurons early after neocortical trauma. Neurobiol Dis 2016; 91:166-81. [PMID: 26956396 DOI: 10.1016/j.nbd.2016.03.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 02/24/2016] [Accepted: 03/02/2016] [Indexed: 12/27/2022] Open
Abstract
Lesioned neuronal circuits form new functional connections after a traumatic brain injury (TBI). In humans and animal models, aberrant excitatory connections that form after TBI may contribute to the pathogenesis of post-traumatic epilepsy. Partial neocortical isolation ("undercut" or "UC") leads to altered neuronal circuitry and network hyperexcitability recorded in vivo and in brain slices from chronically lesioned neocortex. Recent data suggest a critical period for maladaptive excitatory circuit formation within the first 3days post UC injury (Graber and Prince 1999, 2004; Li et al. 2011, 2012b). The present study focuses on alterations in excitatory connectivity within this critical period. Immunoreactivity (IR) for growth-associated protein (GAP)-43 was increased in the UC cortex 3days after injury. Some GAP-43-expressing excitatory terminals targeted the somata of layer V pyramidal (Pyr) neurons, a domain usually innervated predominantly by inhibitory terminals. Immunocytochemical analysis of pre- and postsynaptic markers showed that putative excitatory synapses were present on somata of these neurons in UC neocortex. Excitatory postsynaptic currents from UC layer V Pyr cells displayed properties consistent with perisomatic inputs and also reflected an increase in the number of synaptic contacts. Laser scanning photostimulation (LSPS) experiments demonstrated reorganized excitatory connectivity after injury within the UC. Concurrent with these changes, spontaneous epileptiform bursts developed in UC slices. Results suggest that aberrant reorganization of excitatory connectivity contributes to early neocortical hyperexcitability in this model. The findings are relevant for understanding the pathophysiology of neocortical post-traumatic epileptogenesis and are important in terms of the timing of potential prophylactic treatments.
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Affiliation(s)
- D Koji Takahashi
- Epilepsy Research Laboratories, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - Feng Gu
- Epilepsy Research Laboratories, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - Isabel Parada
- Epilepsy Research Laboratories, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - Shri Vyas
- Epilepsy Research Laboratories, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, United States
| | - David A Prince
- Epilepsy Research Laboratories, Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, United States.
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19
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Nejad GG, Vastyanov RS, Shahabi P, Alipoor MR, Pakdel FG. Abnormalities in the GABAergic Inhibitory System Leading to the Development of Spike-Wave Discharges in the Somatosensory Cortex of Wag/Rij Rats. NEUROPHYSIOLOGY+ 2016. [DOI: 10.1007/s11062-016-9555-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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20
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Prince D, Gu F, Parada I. Antiepileptogenic repair of excitatory and inhibitory synaptic connectivity after neocortical trauma. PROGRESS IN BRAIN RESEARCH 2016; 226:209-27. [DOI: 10.1016/bs.pbr.2016.03.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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21
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Yu J, Proddutur A, Swietek B, Elgammal FS, Santhakumar V. Functional Reduction in Cannabinoid-Sensitive Heterotypic Inhibition of Dentate Basket Cells in Epilepsy: Impact on Network Rhythms. Cereb Cortex 2015; 26:4229-4314. [PMID: 26400918 DOI: 10.1093/cercor/bhv199] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Strong perisomatic inhibition by fast-spiking basket cells (FS-BCs) regulates dentate throughput. Homotypic FS-BC interconnections that support gamma oscillations, and heterotypic inputs from diverse groups of interneurons that receive extensive neurochemical regulation, together, shape FS-BC activity patterns. However, whether seizures precipitate functional changes in inhibitory networks and contribute to abnormal network activity in epilepsy is not known. In the first recordings from dentate interneuronal pairs in a model of temporal lobe epilepsy, we demonstrate that status epilepticus (SE) selectively compromises GABA release at synapses from dentate accommodating interneurons (AC-INs) to FS-BCs, while efficacy of homotypic FS-BC synapses is unaltered. The functional decrease in heterotypic cannabinoid receptor type 1 (CB1R)-sensitive inhibition of FS-BCs resulted from enhanced baseline GABAB-mediated suppression of synaptic release after SE. The frequency of CB1R-sensitive inhibitory synaptic events in FS-BCs was depressed early after SE induction and remained reduced in epileptic rats. In biologically based simulations of heterogeneous inhibitory networks and excitatory-inhibitory cell networks, experimentally identified decrease in reliability of AC-IN to FS-BCs synaptic release reduced theta power and theta-gamma coupling and enhanced gamma coherence. Thus, the experimentally identified functional reduction in heterotypic inhibition of FS-BCs can contribute to compromised network oscillations in epilepsy and could precipitate memory and cognitive co-morbidities.
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Affiliation(s)
- Jiandong Yu
- Center for Neuropsychiatric Diseases, Institute of Life Science, Nanchang University, Nanchang 330031, China Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Archana Proddutur
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Bogumila Swietek
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Fatima S Elgammal
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
| | - Vijayalakshmi Santhakumar
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers New Jersey Medical School, Newark, NJ 07103, USA
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22
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Martens MA, Boesmans W, Vanden Berghe P. Calcium imaging at kHz frame rates resolves millisecond timing in neuronal circuits and varicosities. BIOMEDICAL OPTICS EXPRESS 2014; 5:2648-2661. [PMID: 25136492 PMCID: PMC4132995 DOI: 10.1364/boe.5.002648] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/10/2014] [Accepted: 07/11/2014] [Indexed: 06/03/2023]
Abstract
We have configured a widefield fast imaging system that allows imaging at 1000 frames per second (512x512 pixels). The system was extended with custom processing tools including a time correlation method to facilitate the analysis of static subcellular compartments (e.g. neuronal varicosities) with enhanced contrast, as well as a dynamic intensity processing (DIP) algorithm that aids in data size reduction and fast visualization and interpretation of timing and directionality in neuronal circuits. This system, together with our custom developed processing tools enables efficient detection of fast physiological events, such as action potential dependent calcium steps. We show, using a specific blocker of nerve communication, that with this setup it is possible to discriminate between a pre and post synaptic event in an all optical way.
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Affiliation(s)
- Michiel A. Martens
- Laboratory for Enteric Neuroscience (LENS),TARGID, University of Leuven, O&N 1 Herestraat 49-box 701, Leuven 3000, Belgium
| | - Werend Boesmans
- Laboratory for Enteric Neuroscience (LENS),TARGID, University of Leuven, O&N 1 Herestraat 49-box 701, Leuven 3000, Belgium
| | - Pieter Vanden Berghe
- Laboratory for Enteric Neuroscience (LENS),TARGID, University of Leuven, O&N 1 Herestraat 49-box 701, Leuven 3000, Belgium
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23
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Jin X, Jiang K, Prince DA. Excitatory and inhibitory synaptic connectivity to layer V fast-spiking interneurons in the freeze lesion model of cortical microgyria. J Neurophysiol 2014; 112:1703-13. [PMID: 24990567 DOI: 10.1152/jn.00854.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A variety of major developmental cortical malformations are closely associated with clinically intractable epilepsy. Pathophysiological aspects of one such disorder, human polymicrogyria, can be modeled by making neocortical freeze lesions (FL) in neonatal rodents, resulting in the formation of microgyri. Previous studies showed enhanced excitatory and inhibitory synaptic transmission and connectivity in cortical layer V pyramidal neurons in the paramicrogyral cortex. In young adult transgenic mice that express green fluorescent protein (GFP) specifically in parvalbumin positive fast-spiking (FS) interneurons, we used laser scanning photostimulation (LSPS) of caged glutamate to map excitatory and inhibitory synaptic connectivity onto FS interneurons in layer V of paramicrogyral cortex in control and FL groups. The proportion of uncaging sites from which excitatory postsynaptic currents (EPSCs) could be evoked (hotspot ratio) increased slightly but significantly in FS cells of the FL vs. control cortex, while the mean amplitude of LSPS-evoked EPSCs at hotspots did not change. In contrast, the hotspot ratio of inhibitory postsynaptic currents (IPSCs) was significantly decreased in FS neurons of the FL cortex. These alterations in synaptic inputs onto FS interneurons may result in an enhanced inhibitory output. We conclude that alterations in synaptic connectivity to cortical layer V FS interneurons do not contribute to hyperexcitability of the FL model. Instead, the enhanced inhibitory output from these neurons may partially offset an earlier demonstrated increase in synaptic excitation of pyramidal cells and thereby maintain a relative balance between excitation and inhibition in the affected cortical circuitry.
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Affiliation(s)
- Xiaoming Jin
- Stark Neurosciences Research Institute, Indiana Spinal Cord and Brain Injury Research Group, Indiana University School of Medicine, Indianapolis, Indiana; Departments of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana; Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California
| | - Kewen Jiang
- Stark Neurosciences Research Institute, Indiana Spinal Cord and Brain Injury Research Group, Indiana University School of Medicine, Indianapolis, Indiana; Department of Neurology, Children's Hospital of the Zhejiang University School of Medicine, Hangzhou, Zhejiang, China; and
| | - David A Prince
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California
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24
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Zhou FW, Roper SN. Reduced chemical and electrical connections of fast-spiking interneurons in experimental cortical dysplasia. J Neurophysiol 2014; 112:1277-90. [PMID: 24944214 DOI: 10.1152/jn.00126.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Aberrant neural connections are regarded as a principal factor contributing to epileptogenesis. This study examined chemical and electrical connections between fast-spiking (FS), parvalbumin (PV)-immunoreactive (FS-PV) interneurons and regular-spiking (RS) neurons (pyramidal neurons or spiny stellate neurons) in a rat model of prenatal irradiation-induced cortical dysplasia. Presynaptic action potentials were evoked by current injection and the elicited unitary inhibitory or excitatory postsynaptic potentials (uIPSPs or uEPSPs) were recorded in the postsynaptic cell. In dysplastic cortex, connection rates between presynaptic FS-PV interneurons and postsynaptic RS neurons and FS-PV interneurons, and uIPSP amplitudes were significantly smaller than controls, but both failure rates and coefficient of variation of uIPSP amplitudes were larger than controls. In contrast, connection rates from RS neurons to FS-PV interneurons and uEPSPs amplitude were similar in the two groups. Assessment of the paired pulse ratio showed a significant decrease in synaptic release probability at FS-PV interneuronal terminals, and the density of terminal boutons on axons of biocytin-filled FS-PV interneurons was also decreased, suggesting presynaptic dysfunction in chemical synapses formed by FS-PV interneurons. Electrical connections were observed between FS-PV interneurons, and the connection rates and coupling coefficients were smaller in dysplastic cortex than controls. In dysplastic cortex, we found a reduced synaptic efficiency for uIPSPs originating from FS-PV interneurons regardless of the type of target cell, and impaired electrical connections between FS-PV interneurons. This expands our understanding of the fundamental impairment of inhibition in this model and may have relevance for certain types of human cortical dysplasia.
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Affiliation(s)
- Fu-Wen Zhou
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida
| | - Steven N Roper
- Department of Neurosurgery and the McKnight Brain Institute, University of Florida, Gainesville, Florida
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25
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Gonzalez-Burgos G, Miyamae T, Pafundo DE, Yoshino H, Rotaru DC, Hoftman G, Datta D, Zhang Y, Hammond M, Sampson AR, Fish KN, Ermentrout GB, Lewis DA. Functional Maturation of GABA Synapses During Postnatal Development of the Monkey Dorsolateral Prefrontal Cortex. Cereb Cortex 2014; 25:4076-93. [PMID: 24904071 DOI: 10.1093/cercor/bhu122] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Development of inhibition onto pyramidal cells may be crucial for the emergence of cortical network activity, including gamma oscillations. In primate dorsolateral prefrontal cortex (DLPFC), inhibitory synaptogenesis starts in utero and inhibitory synapse density reaches adult levels before birth. However, in DLPFC, the expression levels of γ-aminobutyric acid (GABA) synapse-related gene products changes markedly during development until young adult age, suggesting a highly protracted maturation of GABA synapse function. Therefore, we examined the development of GABA synapses by recording GABAAR-mediated inhibitory postsynaptic currents (GABAAR-IPSCs) from pyramidal cells in the DLPFC of neonatal, prepubertal, peripubertal, and adult macaque monkeys. We found that the decay of GABAAR-IPSCs, possibly including those from parvalbumin-positive GABA neurons, shortened by prepubertal age, while their amplitude increased until the peripubertal period. Interestingly, both GABAAR-mediated quantal response size, estimated by miniature GABAAR-IPSCs, and the density of GABAAR synaptic appositions, measured with immunofluorescence microscopy, were stable with age. Simulations in a computational model network with constant GABA synapse density showed that the developmental changes in GABAAR-IPSC properties had a significant impact on oscillatory activity and predicted that, whereas DLPFC circuits can generate gamma frequency oscillations by prepubertal age, mature levels of gamma band power are attained at late stages of development.
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Affiliation(s)
- Guillermo Gonzalez-Burgos
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Takeaki Miyamae
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Diego E Pafundo
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, USA
| | - Hiroki Yoshino
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Psychiatry, Nara Medical University, Japan
| | - Diana C Rotaru
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA Current address: Department of Integrative Neurophysiology, Vrije Universiteit, Amsterdam, Netherlands
| | - Gil Hoftman
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Dibyadeep Datta
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Yun Zhang
- Department of Statistics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Mahjub Hammond
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Allan R Sampson
- Department of Statistics, University of Pittsburgh, Pittsburgh, PA, USA
| | - Kenneth N Fish
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - G Bard Ermentrout
- Department of Mathematics, University of Pittsburgh, Pittsburgh, PA, USA
| | - David A Lewis
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Cantu D, Walker K, Andresen L, Taylor-Weiner A, Hampton D, Tesco G, Dulla CG. Traumatic Brain Injury Increases Cortical Glutamate Network Activity by Compromising GABAergic Control. Cereb Cortex 2014; 25:2306-20. [PMID: 24610117 DOI: 10.1093/cercor/bhu041] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Traumatic brain injury (TBI) is a major risk factor for developing pharmaco-resistant epilepsy. Although disruptions in brain circuitry are associated with TBI, the precise mechanisms by which brain injury leads to epileptiform network activity is unknown. Using controlled cortical impact (CCI) as a model of TBI, we examined how cortical excitability and glutamatergic signaling was altered following injury. We optically mapped cortical glutamate signaling using FRET-based glutamate biosensors, while simultaneously recording cortical field potentials in acute brain slices 2-4 weeks following CCI. Cortical electrical stimulation evoked polyphasic, epileptiform field potentials and disrupted the input-output relationship in deep layers of CCI-injured cortex. High-speed glutamate biosensor imaging showed that glutamate signaling was significantly increased in the injured cortex. Elevated glutamate responses correlated with epileptiform activity, were highest directly adjacent to the injury, and spread via deep cortical layers. Immunoreactivity for markers of GABAergic interneurons were significantly decreased throughout CCI cortex. Lastly, spontaneous inhibitory postsynaptic current frequency decreased and spontaneous excitatory postsynaptic current increased after CCI injury. Our results suggest that specific cortical neuronal microcircuits may initiate and facilitate the spread of epileptiform activity following TBI. Increased glutamatergic signaling due to loss of GABAergic control may provide a mechanism by which TBI can give rise to post-traumatic epilepsy.
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Affiliation(s)
- David Cantu
- Department of Neuroscience, Tufts University School of Medicine, SC201, Boston, MA 02111, USA
| | - Kendall Walker
- Department of Neuroscience, Alzheimer's Disease Research Laboratory, Tufts University School of Medicine, A305, Boston, MA 02111, USA
| | - Lauren Andresen
- Department of Neuroscience, Tufts University School of Medicine, SC201, Boston, MA 02111, USA Program in Neuroscience at the Sackler School of Biomedical Sciences, Tufts University
| | - Amaro Taylor-Weiner
- Department of Neuroscience, Tufts University School of Medicine, SC201, Boston, MA 02111, USA Current address: Broad Institute, Cambridge, MA 02142, USA
| | - David Hampton
- Department of Neuroscience, Tufts University School of Medicine, SC201, Boston, MA 02111, USA
| | - Giuseppina Tesco
- Department of Neuroscience, Alzheimer's Disease Research Laboratory, Tufts University School of Medicine, A305, Boston, MA 02111, USA
| | - Chris G Dulla
- Department of Neuroscience, Tufts University School of Medicine, SC201, Boston, MA 02111, USA
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Jiang M, Yang M, Yin L, Zhang X, Shu Y. Developmental reduction of asynchronous GABA release from neocortical fast-spiking neurons. ACTA ACUST UNITED AC 2013; 25:258-70. [PMID: 23968835 DOI: 10.1093/cercor/bht236] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Delayed asynchronous release (AR) evoked by bursts of presynaptic action potentials (APs) occurs in certain types of hippocampal and neocortical inhibitory interneurons. Previous studies showed that AR provides long-lasting inhibition and desynchronizes the activity in postsynaptic cells. However, whether AR undergoes developmental change remains unknown. In this study, we performed whole-cell recording from fast-spiking (FS) interneurons and pyramidal cells (PCs) in prefrontal cortical slices obtained from juvenile and adult rats. In response to AP trains in FS neurons, AR occurred at their output synapses during both age periods, including FS autapses and FS-PC synapses; however, the AR strength was significantly weaker in adults than that in juveniles. Further experiments suggested that the reduction of AR in adult animals could be attributable to the rapid clearance of residual Ca(2+) from presynaptic terminals. Together, our results revealed that the AR strength was stronger at juvenile but weaker in adult, possibly resulting from changes in presynaptic Ca(2+) dynamics. AR changes may meet the needs of the neural network to generate different types of oscillations for cortical processing at distinct behavioral states.
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Affiliation(s)
- Man Jiang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Mingpo Yang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Luping Yin
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Xiaohui Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
| | - Yousheng Shu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, P. R. China
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