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Lin S, Hari K, Black S, Khatmi A, Fouad K, Gorassini MA, Li Y, Lucas-Osma AM, Fenrich KK, Bennett DJ. Locomotor-related propriospinal V3 neurons produce primary afferent depolarization and modulate sensory transmission to motoneurons. J Neurophysiol 2023; 130:799-823. [PMID: 37609680 PMCID: PMC10650670 DOI: 10.1152/jn.00482.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 08/21/2023] [Accepted: 08/22/2023] [Indexed: 08/24/2023] Open
Abstract
When a muscle is stretched, sensory feedback not only causes reflexes but also leads to a depolarization of sensory afferents throughout the spinal cord (primary afferent depolarization, PAD), readying the whole limb for further disturbances. This sensory-evoked PAD is thought to be mediated by a trisynaptic circuit, where sensory input activates first-order excitatory neurons that activate GABAergic neurons that in turn activate GABAA receptors on afferents to cause PAD, though the identity of these first-order neurons is unclear. Here, we show that these first-order neurons include propriospinal V3 neurons, as they receive extensive sensory input and in turn innervate GABAergic neurons that cause PAD, because optogenetic activation or inhibition of V3 neurons in mice mimics or inhibits sensory-evoked PAD, respectively. Furthermore, persistent inward sodium currents intrinsic to V3 neurons prolong their activity, explaining the prolonged duration of PAD. Also, local optogenetic activation of V3 neurons at one segment causes PAD in other segments, due to the long propriospinal tracts of these neurons, helping to explain the radiating nature of PAD. This in turn facilitates monosynaptic reflex transmission to motoneurons across the spinal cord. In addition, V3 neurons directly innervate proprioceptive afferents (including Ia), causing a glutamate receptor-mediated PAD (glutamate PAD). Finally, increasing the spinal cord excitability with either GABAA receptor blockers or chronic spinal cord injury causes an increase in the glutamate PAD. Overall, we show the V3 neuron has a prominent role in modulating sensory transmission, in addition to its previously described role in locomotion.NEW & NOTEWORTHY Locomotor-related propriospinal neurons depolarize sensory axons throughout the spinal cord by either direct glutamatergic axoaxonic contacts or indirect innervation of GABAergic neurons that themselves form axoaxonic contacts on sensory axons. This depolarization (PAD) increases sensory transmission to motoneurons throughout the spinal cord, readying the sensorimotor system for external disturbances. The glutamate-mediated PAD is particularly adaptable, increasing with either an acute block of GABA receptors or chronic spinal cord injury, suggesting a role in motor recovery.
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Affiliation(s)
- Shihao Lin
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Krishnapriya Hari
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Sophie Black
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Aysan Khatmi
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Karim Fouad
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Monica A Gorassini
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Department of Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Ana M Lucas-Osma
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada
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Domínguez-Oliva A, Mota-Rojas D, Hernández-Avalos I, Mora-Medina P, Olmos-Hernández A, Verduzco-Mendoza A, Casas-Alvarado A, Whittaker AL. The neurobiology of pain and facial movements in rodents: Clinical applications and current research. Front Vet Sci 2022; 9:1016720. [PMID: 36246319 PMCID: PMC9556725 DOI: 10.3389/fvets.2022.1016720] [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: 08/11/2022] [Accepted: 09/12/2022] [Indexed: 11/30/2022] Open
Abstract
One of the most controversial aspects of the use of animals in science is the production of pain. Pain is a central ethical concern. The activation of neural pathways involved in the pain response has physiological, endocrine, and behavioral consequences, that can affect both the health and welfare of the animals, as well as the validity of research. The strategy to prevent these consequences requires understanding of the nociception process, pain itself, and how assessment can be performed using validated, non-invasive methods. The study of facial expressions related to pain has undergone considerable study with the finding that certain movements of the facial muscles (called facial action units) are associated with the presence and intensity of pain. This review, focused on rodents, discusses the neurobiology of facial expressions, clinical applications, and current research designed to better understand pain and the nociceptive pathway as a strategy for implementing refinement in biomedical research.
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Affiliation(s)
- Adriana Domínguez-Oliva
- Master in Science Program “Maestría en Ciencias Agropecuarias”, Universidad Autónoma Metropolitana, Mexico City, Mexico
| | - Daniel Mota-Rojas
- Neurophysiology, Behavior and Animal Welfare Assesment, DPAA, Universidad Autónoma Metropolitana, Mexico City, Mexico
- *Correspondence: Daniel Mota-Rojas
| | - Ismael Hernández-Avalos
- Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico
| | - Patricia Mora-Medina
- Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Mexico
| | - Adriana Olmos-Hernández
- Division of Biotechnology-Bioterio and Experimental Surgery, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, Mexico City, Mexico
| | - Antonio Verduzco-Mendoza
- Division of Biotechnology-Bioterio and Experimental Surgery, Instituto Nacional de Rehabilitación Luis Guillermo Ibarra Ibarra, Mexico City, Mexico
| | - Alejandro Casas-Alvarado
- Neurophysiology, Behavior and Animal Welfare Assesment, DPAA, Universidad Autónoma Metropolitana, Mexico City, Mexico
| | - Alexandra L. Whittaker
- School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia
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Le Ray D, Bertrand SS, Dubuc R. Cholinergic Modulation of Locomotor Circuits in Vertebrates. Int J Mol Sci 2022; 23:ijms231810738. [PMID: 36142651 PMCID: PMC9501616 DOI: 10.3390/ijms231810738] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 11/24/2022] Open
Abstract
Locomotion is a basic motor act essential for survival. Amongst other things, it allows animals to move in their environment to seek food, escape predators, or seek mates for reproduction. The neural mechanisms involved in the control of locomotion have been examined in many vertebrate species and a clearer picture is progressively emerging. The basic muscle synergies responsible for propulsion are generated by neural networks located in the spinal cord. In turn, descending supraspinal inputs are responsible for starting, maintaining, and stopping locomotion as well as for steering and controlling speed. Several neurotransmitter systems play a crucial role in modulating the neural activity during locomotion. For instance, cholinergic inputs act both at the spinal and supraspinal levels and the underlying mechanisms are the focus of the present review. Much information gained on supraspinal cholinergic modulation of locomotion was obtained from the lamprey model. Nicotinic cholinergic inputs increase the level of excitation of brainstem descending command neurons, the reticulospinal neurons (RSNs), whereas muscarinic inputs activate a select group of hindbrain neurons that project to the RSNs to boost their level of excitation. Muscarinic inputs also reduce the transmission of sensory inputs in the brainstem, a phenomenon that could help in sustaining goal directed locomotion. In the spinal cord, intrinsic cholinergic inputs strongly modulate the activity of interneurons and motoneurons to control the locomotor output. Altogether, the present review underlines the importance of the cholinergic inputs in the modulation of locomotor activity in vertebrates.
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Affiliation(s)
- Didier Le Ray
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
- Correspondence: (D.L.R.); (R.D.)
| | - Sandrine S. Bertrand
- Institut des Neurosciences Cognitives et Intégratives d’Aquitaine (INCIA), UMR 5287, Université de Bordeaux-CNRS, F-33076 Bordeaux, France
| | - Réjean Dubuc
- Department of Neurosciences, Université de Montréal, Montréal, QC H3C 3J7, Canada
- Department of Physical Activity Sciences and Research Group in Adapted Physical Activity, Université du Québec à Montréal, Montréal, QC H3C 3P8, Canada
- Correspondence: (D.L.R.); (R.D.)
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Moreno-Lopez Y, Bichara C, Delbecq G, Isope P, Cordero-Erausquin M. The corticospinal tract primarily modulates sensory inputs in the mouse lumbar cord. eLife 2021; 10:65304. [PMID: 34497004 PMCID: PMC8439650 DOI: 10.7554/elife.65304] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Accepted: 07/27/2021] [Indexed: 01/01/2023] Open
Abstract
It is generally assumed that the main function of the corticospinal tract (CST) is to convey motor commands to bulbar or spinal motoneurons. Yet the CST has also been shown to modulate sensory signals at their entry point in the spinal cord through primary afferent depolarization (PAD). By sequentially investigating different routes of corticofugal pathways through electrophysiological recordings and an intersectional viral strategy, we here demonstrate that motor and sensory modulation commands in mice belong to segregated paths within the CST. Sensory modulation is executed exclusively by the CST via a population of lumbar interneurons located in the deep dorsal horn. In contrast, the cortex conveys the motor command via a relay in the upper spinal cord or supraspinal motor centers. At lumbar level, the main role of the CST is thus the modulation of sensory inputs, which is an essential component of the selective tuning of sensory feedback used to ensure well-coordinated and skilled movement.
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Affiliation(s)
- Yunuen Moreno-Lopez
- Institut des Neurosciences Cellulaires et Intégrées, CNRS - Université de Strasbourg, Strasbourg, France
| | - Charlotte Bichara
- Institut des Neurosciences Cellulaires et Intégrées, CNRS - Université de Strasbourg, Strasbourg, France
| | - Gilles Delbecq
- Institut des Neurosciences Cellulaires et Intégrées, CNRS - Université de Strasbourg, Strasbourg, France
| | - Philippe Isope
- Institut des Neurosciences Cellulaires et Intégrées, CNRS - Université de Strasbourg, Strasbourg, France
| | - Matilde Cordero-Erausquin
- Institut des Neurosciences Cellulaires et Intégrées, CNRS - Université de Strasbourg, Strasbourg, France
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