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Hari K, Lucas-Osma AM, Metz K, Lin S, Pardell N, Roszko DA, Black S, Minarik A, Singla R, Stephens MJ, Pearce RA, Fouad K, Jones KE, Gorassini MA, Fenrich KK, Li Y, Bennett DJ. GABA facilitates spike propagation through branch points of sensory axons in the spinal cord. Nat Neurosci 2022; 25:1288-1299. [PMID: 36163283 PMCID: PMC10042549 DOI: 10.1038/s41593-022-01162-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Accepted: 08/11/2022] [Indexed: 11/09/2022]
Abstract
Movement and posture depend on sensory feedback that is regulated by specialized GABAergic neurons (GAD2+) that form axo-axonic contacts onto myelinated proprioceptive sensory axons and are thought to be inhibitory. However, we report here that activating GAD2+ neurons directly with optogenetics or indirectly by cutaneous stimulation actually facilitates sensory feedback to motor neurons in rodents and humans. GABAA receptors located at or near nodes of Ranvier of sensory axons cause this facilitation by preventing spike propagation failure at the many axon branch points, which is otherwise common without GABA. In contrast, GABAA receptors are generally lacking from axon terminals and so cannot inhibit transmitter release onto motor neurons, unlike GABAB receptors that cause presynaptic inhibition. GABAergic innervation near nodes and branch points allows individual branches to function autonomously, with GAD2+ neurons regulating which branches conduct, adding a computational layer to the neuronal networks generating movement and likely generalizing to other central nervous system axons.
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Affiliation(s)
- Krishnapriya Hari
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Ana M Lucas-Osma
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - Krista Metz
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Shihao Lin
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Noah Pardell
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - David A Roszko
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Sophie Black
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Anna Minarik
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Marilee J Stephens
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Robert A Pearce
- Department of Anesthesiology, University of Wisconsin-Madison, Madison, WI, USA
| | - Karim Fouad
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - Kelvin E Jones
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Monica A Gorassini
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.,Department of Cell Biology, Emory University, Atlanta, GA, USA
| | - David J Bennett
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada. .,Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada.
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2
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Wälchli T, Bisschop J, Miettinen A, Ulmann-Schuler A, Hintermüller C, Meyer EP, Krucker T, Wälchli R, Monnier PP, Carmeliet P, Vogel J, Stampanoni M. Hierarchical imaging and computational analysis of three-dimensional vascular network architecture in the entire postnatal and adult mouse brain. Nat Protoc 2021; 16:4564-4610. [PMID: 34480130 DOI: 10.1038/s41596-021-00587-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Accepted: 06/08/2021] [Indexed: 02/08/2023]
Abstract
The formation of new blood vessels and the establishment of vascular networks are crucial during brain development, in the adult healthy brain, as well as in various diseases of the central nervous system. Here, we describe a step-by-step protocol for our recently developed method that enables hierarchical imaging and computational analysis of vascular networks in postnatal and adult mouse brains. The different stages of the procedure include resin-based vascular corrosion casting, scanning electron microscopy, synchrotron radiation and desktop microcomputed tomography imaging, and computational network analysis. Combining these methods enables detailed visualization and quantification of the 3D brain vasculature. Network features such as vascular volume fraction, branch point density, vessel diameter, length, tortuosity and directionality as well as extravascular distance can be obtained at any developmental stage from the early postnatal to the adult brain. This approach can be used to provide a detailed morphological atlas of the entire mouse brain vasculature at both the postnatal and the adult stage of development. Our protocol allows the characterization of brain vascular networks separately for capillaries and noncapillaries. The entire protocol, from mouse perfusion to vessel network analysis, takes ~10 d.
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Affiliation(s)
- Thomas Wälchli
- Group of CNS Angiogenesis and Neurovascular Link, Neuroscience Center Zurich, and Division of Neurosurgery, University and University Hospital Zurich, Zurich, Switzerland. .,Division of Neurosurgery, University Hospital Zurich, Zurich, Switzerland. .,Group Brain Vasculature and Perivascular Niche, Division of Experimental and Translational Neuroscience, Krembil Brain Institute, Krembil Research Institute, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada. .,Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
| | - Jeroen Bisschop
- Group of CNS Angiogenesis and Neurovascular Link, Neuroscience Center Zurich, and Division of Neurosurgery, University and University Hospital Zurich, Zurich, Switzerland.,Division of Neurosurgery, University Hospital Zurich, Zurich, Switzerland.,Group Brain Vasculature and Perivascular Niche, Division of Experimental and Translational Neuroscience, Krembil Brain Institute, Krembil Research Institute, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada.,Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Arttu Miettinen
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland.,Department of Physics, University of Jyväskylä, Jyväskylä, Finland
| | | | | | - Eric P Meyer
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Thomas Krucker
- Novartis Institutes for BioMedical Research Inc, Emeryville, CA, USA
| | - Regula Wälchli
- Department of Dermatology, Pediatric Skin Center, University Children's Hospital Zurich, Zurich, Switzerland
| | - Philippe P Monnier
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.,Krembil Research Institute, Vision Division, Krembil Discovery Tower, Toronto, Ontario, Canada.,Department of Ophthalmology and Vision Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Peter Carmeliet
- Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology, KU Leuven, Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, VIB Center for Cancer Biology, VIB, Leuven, Belgium
| | - Johannes Vogel
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Marco Stampanoni
- Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.,Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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Lucas-Osma AM, Li Y, Lin S, Black S, Singla R, Fouad K, Fenrich KK, Bennett DJ. Extrasynaptic α 5GABA A receptors on proprioceptive afferents produce a tonic depolarization that modulates sodium channel function in the rat spinal cord. J Neurophysiol 2018; 120:2953-2974. [PMID: 30256739 DOI: 10.1152/jn.00499.2018] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Activation of GABAA receptors on sensory axons produces a primary afferent depolarization (PAD) that modulates sensory transmission in the spinal cord. While axoaxonic synaptic contacts of GABAergic interneurons onto afferent terminals have been extensively studied, less is known about the function of extrasynaptic GABA receptors on afferents. Thus, we examined extrasynaptic α5GABAA receptors on low-threshold proprioceptive (group Ia) and cutaneous afferents. Afferents were impaled with intracellular electrodes and filled with neurobiotin in the sacrocaudal spinal cord of rats. Confocal microscopy was used to reconstruct the afferents and locate immunolabelled α5GABAA receptors. In all afferents α5GABAA receptors were found throughout the extensive central axon arbors. They were most densely located at branch points near sodium channel nodes, including in the dorsal horn. Unexpectedly, proprioceptive afferent terminals on motoneurons had a relative lack of α5GABAA receptors. When recording intracellularly from these afferents, blocking α5GABAA receptors (with L655708, gabazine, or bicuculline) hyperpolarized the afferents, as did blocking neuronal activity with tetrodotoxin, indicating a tonic GABA tone and tonic PAD. This tonic PAD was increased by repeatedly stimulating the dorsal root at low rates and remained elevated for many seconds after the stimulation. It is puzzling that tonic PAD arises from α5GABAA receptors located far from the afferent terminal where they can have relatively little effect on terminal presynaptic inhibition. However, consistent with the nodal location of α5GABAA receptors, we find tonic PAD helps produce sodium spikes that propagate antidromically out the dorsal roots, and we suggest that it may well be involved in assisting spike transmission in general. NEW & NOTEWORTHY GABAergic neurons are well known to form synaptic contacts on proprioceptive afferent terminals innervating motoneurons and to cause presynaptic inhibition. However, the particular GABA receptors involved are unknown. Here, we examined the distribution of extrasynaptic α5GABAA receptors on proprioceptive Ia afferents. Unexpectedly, these receptors were found preferentially near nodal sodium channels throughout the afferent and were largely absent from afferent terminals. These receptors produced a tonic afferent depolarization that modulated sodium spikes, consistent with their location.
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Affiliation(s)
- Ana M Lucas-Osma
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Shihao Lin
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Sophie Black
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Karim Fouad
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute and Faculty of Rehabilitation Medicine, University of Alberta , Edmonton, AB , Canada
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Wälchli T, Ulmann-Schuler A, Hintermüller C, Meyer E, Stampanoni M, Carmeliet P, Emmert MY, Bozinov O, Regli L, Schwab ME, Vogel J, Hoerstrup SP. Nogo-A regulates vascular network architecture in the postnatal brain. J Cereb Blood Flow Metab 2017; 37:614-631. [PMID: 27927704 PMCID: PMC5381465 DOI: 10.1177/0271678x16675182] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Recently, we discovered a new role for the well-known axonal growth inhibitory molecule Nogo-A as a negative regulator of angiogenesis in the developing central nervous system. However, how Nogo-A affected the three-dimensional (3D) central nervous system (CNS) vascular network architecture remained unknown. Here, using vascular corrosion casting, hierarchical, synchrotron radiation μCT-based network imaging and computer-aided network analysis, we found that genetic ablation of Nogo-A significantly increased the three-dimensional vascular volume fraction in the postnatal day 10 (P10) mouse brain. More detailed analysis of the cerebral cortex revealed that this effect was mainly due to an increased number of capillaries and capillary branchpoints. Interestingly, other vascular parameters such as vessel diameter, -length, -tortuosity, and -volume were comparable between both genotypes for non-capillary vessels and capillaries. Taken together, our three-dimensional data showing more vessel segments and branchpoints at unchanged vessel morphology suggest that stimulated angiogenesis upon Nogo-A gene deletion results in the insertion of complete capillary micro-networks and not just single vessels into existing vascular networks. These findings significantly enhance our understanding of how angiogenesis, vascular remodeling, and three-dimensional vessel network architecture are regulated during central nervous system development. Nogo-A may therefore be a potential novel target for angiogenesis-dependent central nervous system pathologies such as brain tumors or stroke.
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Affiliation(s)
- Thomas Wälchli
- 1 Group of CNS Angiogenesis and Neurovascular Link, and Physician-Scientist Program, Institute for Regenerative Medicine, Neuroscience Center Zurich, and Division of Neurosurgery, University and University Hospital Zurich, Switzerland, and Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland.,2 Division of Neurosurgery and Laboratory of Molecular Neuro-Oncology, University Hospital Zurich, Zurich, Switzerland.,3 Brain Research Institute, University of Zurich and Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | | | | | - Eric Meyer
- 3 Brain Research Institute, University of Zurich and Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Marco Stampanoni
- 6 Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.,7 Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Peter Carmeliet
- 8 Laboratory of Angiogenesis and Vascular Metabolism, Vesalius Research Center, Leuven, Belgium.,9 Department of Oncology, Laboratory of Angiogenesis and Neurovascular Link, Leuven, Belgium
| | - Maximilian Y Emmert
- 10 Institute for Regenerative Medicine and Clinic for Cardiovascular Surgery, University Hospital Zurich.,11 Wyss Translational Center Zurich, University of Zurich and Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Oliver Bozinov
- 2 Division of Neurosurgery and Laboratory of Molecular Neuro-Oncology, University Hospital Zurich, Zurich, Switzerland
| | - Luca Regli
- 2 Division of Neurosurgery and Laboratory of Molecular Neuro-Oncology, University Hospital Zurich, Zurich, Switzerland
| | - Martin E Schwab
- 3 Brain Research Institute, University of Zurich and Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Johannes Vogel
- 12 Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Simon P Hoerstrup
- 10 Institute for Regenerative Medicine and Clinic for Cardiovascular Surgery, University Hospital Zurich.,11 Wyss Translational Center Zurich, University of Zurich and Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
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