1
|
Zhang Y, Heylen L, Partoens M, Mills JD, Kaminski RM, Godard P, Gillard M, de Witte PAM, Siekierska A. Connectivity Mapping Using a Novel sv2a Loss-of-Function Zebrafish Epilepsy Model as a Powerful Strategy for Anti-epileptic Drug Discovery. Front Mol Neurosci 2022; 15:881933. [PMID: 35686059 PMCID: PMC9172968 DOI: 10.3389/fnmol.2022.881933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 04/08/2022] [Indexed: 12/03/2022] Open
Abstract
Synaptic vesicle glycoprotein 2A (SV2A) regulates action potential-dependent neurotransmitter release and is commonly known as the primary binding site of an approved anti-epileptic drug, levetiracetam. Although several rodent knockout models have demonstrated the importance of SV2A for functional neurotransmission, its precise physiological function and role in epilepsy pathophysiology remains to be elucidated. Here, we present a novel sv2a knockout model in zebrafish, a vertebrate with complementary advantages to rodents. We demonstrated that 6 days post fertilization homozygous sv2a–/– mutant zebrafish larvae, but not sv2a+/– and sv2a+/+ larvae, displayed locomotor hyperactivity and spontaneous epileptiform discharges, however, no major brain malformations could be observed. A partial rescue of this epileptiform brain activity could be observed after treatment with two commonly used anti-epileptic drugs, valproic acid and, surprisingly, levetiracetam. This observation indicated that additional targets, besides Sv2a, maybe are involved in the protective effects of levetiracetam against epileptic seizures. Furthermore, a transcriptome analysis provided insights into the neuropathological processes underlying the observed epileptic phenotype. While gene expression profiling revealed only one differentially expressed gene (DEG) between wildtype and sv2a+/– larvae, there were 4386 and 3535 DEGs between wildtype and sv2a–/–, and sv2a+/– and sv2a–/– larvae, respectively. Pathway and gene ontology (GO) enrichment analysis between wildtype and sv2a–/– larvae revealed several pathways and GO terms enriched amongst up- and down-regulated genes, including MAPK signaling, synaptic vesicle cycle, and extracellular matrix organization, all known to be involved in epileptogenesis and epilepsy. Importantly, we used the Connectivity map database to identify compounds with opposing gene signatures compared to the one observed in sv2a–/– larvae, to finally rescue the epileptic phenotype. Two out of three selected compounds rescued electrographic discharges in sv2a–/– larvae, while negative controls did not. Taken together, our results demonstrate that sv2a deficiency leads to increased seizure vulnerability and provide valuable insight into the functional importance of sv2a in the brain in general. Furthermore, we provided evidence that the concept of connectivity mapping represents an attractive and powerful approach in the discovery of novel compounds against epilepsy.
Collapse
Affiliation(s)
- Yifan Zhang
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
| | - Lise Heylen
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
| | - Michèle Partoens
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
| | - James D. Mills
- Department of Neuropathology, Amsterdam Neuroscience, Amsterdam UMC, University of Amsterdam, Amsterdam, Netherlands
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom
- Chalfont Centre for Epilepsy, Chalfont St Peter, United Kingdom
| | - Rafal M. Kaminski
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Kraków, Poland
- UCB Pharma, Braine-l’Alleud, Belgium
| | | | | | - Peter A. M. de Witte
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
- *Correspondence: Peter A. M. de Witte,
| | - Aleksandra Siekierska
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
- Aleksandra Siekierska,
| |
Collapse
|
2
|
Momose-Sato Y, Sato K. Prenatal exposure to nicotine disrupts synaptic network formation by inhibiting spontaneous correlated wave activity. IBRO Rep 2020; 9:14-23. [PMID: 32642591 PMCID: PMC7334560 DOI: 10.1016/j.ibror.2020.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 06/20/2020] [Indexed: 11/28/2022] Open
Abstract
Correlated spontaneous activity propagating over a wide region of the central nervous system is expressed during a specific period of embryonic development. We previously demonstrated using an optical imaging technique with a voltage-sensitive dye that this wave-like activity, which we referred to as the depolarization wave, is fundamentally involved in the early process of synaptic network formation. We found that the in ovo application of bicuculline/strychnine or d-tubocurarine, which blocked the neurotransmitters mediating the wave, significantly reduced functional synaptic expression in the brainstem sensory nucleus. This result, particularly for d-tubocurarine, an antagonist of nicotinic acetylcholine receptors, suggested that prenatal nicotine exposure associated with maternal smoking affects the development of neural circuit formation by interfering with the correlated wave. In the present study, we tested this hypothesis by examining the effects of nicotine on the correlated activity and assessing the chronic action of nicotine in ovo on functional synaptic expression along the vagal sensory pathway. In ovo observations of chick embryo behavior and electrical recording using in vitro preparations showed that the application of nicotine transiently increased embryonic movements and electrical bursts associated with the wave, but subsequently inhibited these activities, suggesting that the dominant action of the drug was to inhibit the wave. Optical imaging with the voltage-sensitive dye showed that the chronic exposure to nicotine in ovo markedly reduced functional synaptic expression in the higher-order sensory nucleus of the vagus nerve, the parabrachial nucleus. The results suggest that prenatal nicotine exposure disrupts the initial formation of the neural circuitry by inhibiting correlated spontaneous wave activity.
Collapse
Key Words
- APV, DL-2-amino-5-phosphonovaleric acid
- CNQX, 6-cyano-7-nitroquinoxaline-2,3-dione
- E, embryonic day (days of incubation in avians and days of pregnancy in mammals)
- EPSP, excitatory postsynaptic potential
- GABA, γ-aminobutyric acid
- In ovo
- NMDA, N-methyl-D-aspartate
- NTS, nucleus of the tractus solitarius
- Nicotine
- Optical recording
- PBN, parabrachial nucleus
- Spontaneous activity
- Synaptic network formation
- Voltage-sensitive dye
- nAChR, nicotinic acetylcholine receptor
Collapse
Affiliation(s)
- Yoko Momose-Sato
- Department of Nutrition and Dietetics, College of Nutrition, Kanto Gakuin University, Kanazawa-ku, Yokohama, 236-8501, Japan
| | - Katsushige Sato
- Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women’s University, Inagi-shi, Tokyo, 206-8511, Japan
| |
Collapse
|
3
|
Cregg JM, Chu KA, Hager LE, Maggard RSJ, Stoltz DR, Edmond M, Alilain WJ, Philippidou P, Landmesser LT, Silver J. A Latent Propriospinal Network Can Restore Diaphragm Function after High Cervical Spinal Cord Injury. Cell Rep 2017; 21:654-665. [PMID: 29045834 PMCID: PMC5687843 DOI: 10.1016/j.celrep.2017.09.076] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 08/08/2017] [Accepted: 09/24/2017] [Indexed: 10/18/2022] Open
Abstract
Spinal cord injury (SCI) above cervical level 4 disrupts descending axons from the medulla that innervate phrenic motor neurons, causing permanent paralysis of the diaphragm. Using an ex vivo preparation in neonatal mice, we have identified an excitatory spinal network that can direct phrenic motor bursting in the absence of medullary input. After complete cervical SCI, blockade of fast inhibitory synaptic transmission caused spontaneous, bilaterally coordinated phrenic bursting. Here, spinal cord glutamatergic neurons were both sufficient and necessary for the induction of phrenic bursts. Direct stimulation of phrenic motor neurons was insufficient to evoke burst activity. Transection and pharmacological manipulations showed that this spinal network acts independently of medullary circuits that normally generate inspiration, suggesting a distinct non-respiratory function. We further show that this "latent" network can be harnessed to restore diaphragm function after high cervical SCI in adult mice and rats.
Collapse
Affiliation(s)
- Jared M Cregg
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Kevin A Chu
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Lydia E Hager
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Rachel S J Maggard
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Daimen R Stoltz
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Michaela Edmond
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Warren J Alilain
- Spinal Cord and Brain Injury Research Center, Department of Neuroscience, University of Kentucky College of Medicine, Lexington, KY 40536, USA
| | - Polyxeni Philippidou
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Lynn T Landmesser
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Jerry Silver
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106, USA.
| |
Collapse
|
4
|
Momose-Sato Y, Sato K. Developmental roles of the spontaneous depolarization wave in synaptic network formation in the embryonic brainstem. Neuroscience 2017; 365:33-47. [PMID: 28951326 DOI: 10.1016/j.neuroscience.2017.09.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 08/29/2017] [Accepted: 09/18/2017] [Indexed: 01/25/2023]
Abstract
One of the earliest activities expressed within the developing central nervous system is a widely propagating wave-like activity, which we referred to as the depolarization wave. Despite considerable consensus concerning the global features of the activity, its physiological role is yet to be clarified. The depolarization wave is expressed during a specific period of functional synaptogenesis, and this developmental profile has led to the hypothesis that the wave plays some roles in synaptic network organization. In the present study, we tested this hypothesis by inhibiting the depolarization wave in ovo and examining its effects on the development of functional synapses in vagus nerve-related brainstem nuclei of the chick embryo. Chronic inhibition of the depolarization wave had no significant effect on the developmental time course, amplitude, and spatial distribution of monosynaptic excitatory postsynaptic potentials in the first-order nuclei of the vagal sensory pathway (the nucleus of the tractus solitarius (NTS) and the contralateral non-NTS region), but reduced polysynaptic responses in the higher-order nucleus (the parabrachial nucleus). These results suggest that the depolarization wave plays an important role in the initial process of functional synaptic expression in the brainstem, especially in the higher-order nucleus of the cranial sensory pathway.
Collapse
Affiliation(s)
- Yoko Momose-Sato
- Department of Nutrition and Dietetics, College of Nutrition, Kanto Gakuin University, Kanazawa-ku, Yokohama 236-8503, Japan.
| | - Katsushige Sato
- Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women's University, Inagi-shi, Tokyo 206-8511, Japan
| |
Collapse
|
5
|
Sato K, Momose-Sato Y. Functiogenesis of the embryonic central nervous system revealed by optical recording with a voltage-sensitive dye. J Physiol Sci 2017; 67:107-119. [PMID: 27623687 PMCID: PMC10717437 DOI: 10.1007/s12576-016-0482-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 08/28/2016] [Indexed: 10/21/2022]
Abstract
Clarification of the functiogenesis of the embryonic central nervous system (CNS) has long been problematic, because conventional electrophysiological techniques have several limitations. First, early embryonic neurons are small and fragile, and the application of microelectrodes is challenging. Second, the simultaneous monitoring of electrical activity from multiple sites is limited, and as a consequence, spatiotemporal response patterns of neural networks cannot be assessed. We have applied multiple-site optical recording with a voltage-sensitive dye to the embryonic CNS and paved a new way to analyze the functiogenesis of the CNS. In this review, we discuss key points of optical recording in the embryonic CNS and introduce recent progress in optical investigations on the embryonic CNS with special emphasis on the development of the chick olfactory system. The studies clearly demonstrate the usefulness of voltage-sensitive dye recording as a powerful tool for elucidating the functional organization of the vertebrate embryonic CNS.
Collapse
Affiliation(s)
- Katsushige Sato
- Department of Health and Nutrition Sciences, Komazawa Women's University Faculty of Human Health, 238 Sakahama, Inagi-shi, Tokyo, 206-8511, Japan.
| | - Yoko Momose-Sato
- Department of Nutrition and Dietetics, College of Nutrition, Kanto Gakuin University, Yokohama, 236-8501, Japan
| |
Collapse
|
6
|
Momose-Sato Y, Sato K. Development of Spontaneous Activity in the Avian Hindbrain. Front Neural Circuits 2016; 10:63. [PMID: 27570506 PMCID: PMC4981603 DOI: 10.3389/fncir.2016.00063] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 07/29/2016] [Indexed: 11/13/2022] Open
Abstract
Spontaneous activity in the developing central nervous system occurs before the brain responds to external sensory inputs, and appears in the hindbrain and spinal cord as rhythmic electrical discharges of cranial and spinal nerves. This spontaneous activity recruits a large population of neurons and propagates like a wave over a wide region of the central nervous system. Here, we review spontaneous activity in the chick hindbrain by focusing on this large-scale synchronized activity. Asynchronous activity that is expressed earlier than the above mentioned synchronized activity and activity originating in midline serotonergic neurons are also briefly mentioned.
Collapse
Affiliation(s)
- Yoko Momose-Sato
- Department of Nutrition and Dietetics, College of Nutrition, Kanto Gakuin University Yokohama, Japan
| | - Katsushige Sato
- Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women's University Tokyo, Japan
| |
Collapse
|
7
|
Gonzalez-Islas C, Garcia-Bereguiain MA, O'Flaherty B, Wenner P. Tonic nicotinic transmission enhances spinal GABAergic presynaptic release and the frequency of spontaneous network activity. Dev Neurobiol 2015; 76:298-312. [PMID: 26061781 DOI: 10.1002/dneu.22315] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 05/26/2015] [Accepted: 06/05/2015] [Indexed: 01/16/2023]
Abstract
Synaptically driven spontaneous network activity (SNA) is observed in virtually all developing networks. Recurrently connected spinal circuits express SNA, which drives fetal movements during a period of development when GABA is depolarizing and excitatory. Blockade of nicotinic acetylcholine receptor (nAChR) activation impairs the expression of SNA and the development of the motor system. It is mechanistically unclear how nicotinic transmission influences SNA, and in this study we tested several mechanisms that could underlie the regulation of SNA by nAChRs. We find evidence that is consistent with our previous work suggesting that cholinergically driven Renshaw cells can initiate episodes of SNA. While Renshaw cells receive strong nicotinic synaptic input, we see very little evidence suggesting other spinal interneurons or motoneurons receive nicotinic input. Rather, we found that nAChR activation tonically enhanced evoked and spontaneous presynaptic release of GABA in the embryonic spinal cord. Enhanced spontaneous and/or evoked release could contribute to increased SNA frequency. Finally, our study suggests that blockade of nAChRs can reduce the frequency of SNA by reducing probability of GABAergic release. This result suggests that the baseline frequency of SNA is maintained through elevated GABA release driven by tonically active nAChRs. Nicotinic receptors regulate GABAergic transmission and SNA, which are critically important for the proper development of the embryonic network. Therefore, our results provide a better mechanistic framework for understanding the motor consequences of fetal nicotine exposure.
Collapse
Affiliation(s)
- Carlos Gonzalez-Islas
- Department of Physiology, Emory University, School of Medicine, Whitehead Bldg, Room 601, Atlanta, Georgia, 30322
| | | | - Brendan O'Flaherty
- Department of Physiology, Emory University, School of Medicine, Whitehead Bldg, Room 601, Atlanta, Georgia, 30322
| | - Peter Wenner
- Department of Physiology, Emory University, School of Medicine, Whitehead Bldg, Room 601, Atlanta, Georgia, 30322
| |
Collapse
|
8
|
Momose-Sato Y, Sato K, Kamino K. Monitoring Population Membrane Potential Signals During Development of the Vertebrate Nervous System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:213-42. [DOI: 10.1007/978-3-319-17641-3_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
|
9
|
Connexin hemichannels contribute to spontaneous electrical activity in the human fetal cortex. Proc Natl Acad Sci U S A 2014; 111:E3919-28. [PMID: 25197082 DOI: 10.1073/pnas.1405253111] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Before the human cortex is able to process sensory information, young postmitotic neurons must maintain occasional bursts of action-potential firing to attract and keep synaptic contacts, to drive gene expression, and to transition to mature membrane properties. Before birth, human subplate (SP) neurons are spontaneously active, displaying bursts of electrical activity (plateau depolarizations with action potentials). Using whole-cell recordings in acute cortical slices, we investigated the source of this early activity. The spontaneous depolarizations in human SP neurons at midgestation (17-23 gestational weeks) were not completely eliminated by tetrodotoxin--a drug that blocks action potential firing and network activity--or by antagonists of glutamatergic, GABAergic, or glycinergic synaptic transmission. We then turned our focus away from standard chemical synapses to connexin-based gap junctions and hemichannels. PCR and immunohistochemical analysis identified the presence of connexins (Cx26/Cx32/Cx36) in the human fetal cortex. However, the connexin-positive cells were not found in clusters but, rather, were dispersed in the SP zone. Also, gap junction-permeable dyes did not diffuse to neighboring cells, suggesting that SP neurons were not strongly coupled to other cells at this age. Application of the gap junction and hemichannel inhibitors octanol, flufenamic acid, and carbenoxolone significantly blocked spontaneous activity. The putative hemichannel antagonist lanthanum alone was a potent inhibitor of the spontaneous activity. Together, these data suggest that connexin hemichannels contribute to spontaneous depolarizations in the human fetal cortex during the second trimester of gestation.
Collapse
|
10
|
Momose-Sato Y, Sato K. Maintenance of the large-scale depolarization wave in the embryonic chick brain against deprivation of the rhythm generator. Neuroscience 2014; 266:186-96. [PMID: 24568731 DOI: 10.1016/j.neuroscience.2014.02.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/11/2014] [Accepted: 02/12/2014] [Indexed: 11/24/2022]
Abstract
Widely correlated spontaneous activity in the developing nervous system is transiently expressed and is considered to play a fundamental role in neural circuit formation. The depolarization wave, which spreads over a long distance along the neuraxis, maximally extending to the lumbosacral cord and forebrain, is an example of this spontaneous activity. Although the depolarization wave is typically initiated in the spinal cord in intact preparations, spontaneous discharges have also been detected in the isolated brainstem. Although this suggests that the brainstem has the ability to generate spontaneous activity, but is paced by a caudal rhythm generator of higher excitability, a number of questions remains. Does brainstem activity simply appear as a passive consequence, or does any active change occur in the brainstem network to compensate for this activity? If the latter is the case, does this compensation occur equally at different developmental stages? Where is the new rhythm generator in the isolated brainstem? To answer these questions, we optically analyzed spatio-temporal patterns of activity detected from the chick brainstem before and after transection at the obex. The results revealed that the depolarization wave was homeostatically maintained, which was characterized by an increase in excitability and/or the number of neurons recruited to the wave. The wave was more easily maintained in younger embryos. Furthermore, we demonstrated that the ability of brainstem neurons to perform such an active compensation was not lost even at the stage when the depolarization wave was no longer observed in the intact brainstem.
Collapse
Affiliation(s)
- Y Momose-Sato
- Department of Health and Nutrition, College of Human Environmental Studies, Kanto Gakuin University, Kanazawa-ku, Yokohama 236-8503, Japan.
| | - K Sato
- Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women's University, Inagi-shi, Tokyo 206-8511, Japan.
| |
Collapse
|
11
|
Stein PSG. Molecular, genetic, cellular, and network functions in the spinal cord and brainstem. Ann N Y Acad Sci 2013; 1279:1-12. [PMID: 23530997 DOI: 10.1111/nyas.12083] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies of the model systems of spinal cord and brainstem reveal molecular, genetic, and cellular mechanisms that are critical for network and behavioral functions in the nervous system. Recent experiments establish the importance of neurogenetics in revealing cellular and network properties. Breakthroughs that utilize direct visualization of neuronal activity and network structure provide new insights. Major discoveries of plasticity in the spinal cord and brainstem contribute to basic neuroscience and, in addition, have promising therapeutic implications.
Collapse
Affiliation(s)
- Paul S G Stein
- Biology Department, Washington University, St. Louis, MO 63130, USA.
| |
Collapse
|
12
|
Momose-Sato Y, Sato K. Large-scale synchronized activity in the embryonic brainstem and spinal cord. Front Cell Neurosci 2013; 7:36. [PMID: 23596392 PMCID: PMC3625830 DOI: 10.3389/fncel.2013.00036] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 03/20/2013] [Indexed: 01/09/2023] Open
Abstract
In the developing central nervous system, spontaneous activity appears well before the brain responds to external sensory inputs. One of the earliest activities is observed in the hindbrain and spinal cord, which is detected as rhythmic electrical discharges of cranial and spinal motoneurons or oscillations of Ca(2+)- and voltage-related optical signals. Shortly after the initial expression, the spontaneous activity appearing in the hindbrain and spinal cord exhibits a large-scale correlated wave that propagates over a wide region of the central nervous system, maximally extending to the lumbosacral cord and to the forebrain. In this review, we describe several aspects of this synchronized activity by focusing on the basic properties, development, origin, propagation pattern, pharmacological characteristics, and possible mechanisms underlying the generation of the activity. These profiles differ from those of the respiratory and locomotion pattern generators observed in the mature brainstem and spinal cord, suggesting that the wave is primordial activity that appears during a specific period of embryonic development and plays some important roles in the development of the central nervous system.
Collapse
Affiliation(s)
- Yoko Momose-Sato
- Department of Health and Nutrition, College of Human Environmental Studies, Kanto Gakuin UniversityYokohama, Japan
| | - Katsushige Sato
- Department of Health and Nutrition Sciences, Faculty of Human Health, Komazawa Women's UniversityTokyo, Japan
| |
Collapse
|
13
|
Watari H, Tose AJ, Bosma MM. Hyperpolarization of resting membrane potential causes retraction of spontaneous Ca(i)²⁺ transients during mouse embryonic circuit development. J Physiol 2012; 591:973-83. [PMID: 23165771 DOI: 10.1113/jphysiol.2012.244954] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Abstract Spontaneous activity supports developmental processes in many brain regions during embryogenesis, and the spatial extent and frequency of the spontaneous activity are tightly regulated by stage. In the developing mouse hindbrain, spontaneous activity propagates widely and the waves can cover the entire hindbrain at E11.5. The activity then retracts to waves that are spatially restricted to the rostral midline at E13.5, before disappearing altogether by E15.5. However, the mechanism of retraction is unknown. We studied passive membrane properties of cells that are spatiotemporally relevant to the pattern of retraction in mouse embryonic hindbrain using whole-cell patch clamp and imaging techniques. We find that membrane excitability progressively decreases due to hyperpolarization of resting membrane potential and increased resting conductance density between E11.5 and E15.5, in a spatiotemporal pattern correlated with the retraction sequence. Retraction can be acutely reversed by membrane depolarization at E15.5, and the induced events propagate similarly to spontaneous activity at earlier stages, though without involving gap junctional coupling. Manipulation of [K(+)](o) or [Cl(-)](o) reveals that membrane potential follows E(K) more closely than E(Cl), suggesting a dominant role for K(+) conductance in the membrane hyperpolarization. Reducing membrane excitability by hyperpolarization of the resting membrane potential and increasing resting conductance are effective mechanisms to desynchronize spontaneous activity in a spatiotemporal manner, while allowing information processing to occur at the synaptic and cellular level.
Collapse
Affiliation(s)
- Hirofumi Watari
- Graduate Program in Neurobiology & Behavior, University of Washington, Seattle, WA 98195, USA
| | | | | |
Collapse
|
14
|
Momose-Sato Y, Nakamori T, Sato K. Spontaneous depolarization wave in the mouse embryo: origin and large-scale propagation over the CNS identified with voltage-sensitive dye imaging. Eur J Neurosci 2012; 35:1230-41. [PMID: 22339904 DOI: 10.1111/j.1460-9568.2012.07997.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spontaneous embryonic movements, called embryonic motility, are produced by correlated spontaneous activity in the cranial and spinal nerves, which is driven by brainstem and spinal networks. Using optical imaging with a voltage-sensitive dye, we have revealed previously that this correlated activity is a widely propagating wave of neural depolarization, which we termed the depolarization wave. We have observed in the chick and rat embryos that the activity spread over an extensive region of the CNS, including the spinal cord, hindbrain, cerebellum, midbrain and forebrain. One important consideration is whether a depolarization wave with similar characteristics occurs in other species, especially in different mammals. Here, we provide evidence for the existence of the depolarization wave in the mouse embryo by showing that the widely propagating wave appeared independently of the localized spontaneous activity detected previously with Ca(2+) imaging. Furthermore, we mapped the origin of the depolarization wave and revealed that the wave generator moved from the rostral spinal cord to the caudal cord as development proceeded, and was later replaced with mature rhythmogenerators. The present study, together with an accompanying paper that describes pharmacological properties of the mouse depolarization wave, shows that a synchronized wave with common characteristics is expressed in different species, suggesting fundamental roles in neural development.
Collapse
Affiliation(s)
- Yoko Momose-Sato
- Department of Health and Nutrition, College of Human Environmental Studies, Kanto Gakuin University, Yokohama 236-8503, Japan.
| | | | | |
Collapse
|