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Metz K, Matos IC, Hari K, Bseis O, Afsharipour B, Lin S, Singla R, Fenrich KK, Li Y, Bennett DJ, Gorassini MA. Post-activation depression from primary afferent depolarization (PAD) produces extensor H-reflex suppression following flexor afferent conditioning. J Physiol 2023; 601:1925-1956. [PMID: 36928599 PMCID: PMC11064783 DOI: 10.1113/jp283706] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 03/09/2023] [Indexed: 03/18/2023] Open
Abstract
Suppression of the extensor H-reflex by flexor afferent conditioning is thought to be produced by a long-lasting inhibition of extensor Ia afferent terminals via GABAA receptor-activated primary afferent depolarization (PAD). Given the recent finding that PAD does not produce presynaptic inhibition of Ia afferent terminals, we examined in 28 participants if H-reflex suppression is instead mediated by post-activation depression of the extensor Ia afferents triggered by PAD-evoked spikes and/or by a long-lasting inhibition of the extensor motoneurons. A brief conditioning vibration of the flexor tendon suppressed both the extensor soleus H-reflex and the tonic discharge of soleus motor units out to 150 ms following the vibration, suggesting that part of the H-reflex suppression during this period was mediated by postsynaptic inhibition of the extensor motoneurons. When activating the flexor afferents electrically to produce conditioning, the soleus H-reflex was also suppressed but only when a short-latency reflex was evoked in the soleus muscle by the conditioning input itself. In mice, a similar short-latency reflex was evoked when optogenetic or afferent activation of GABAergic (GAD2+ ) neurons produced a large enough PAD to evoke orthodromic spikes in the test Ia afferents, causing post-activation depression of subsequent monosynaptic EPSPs. The long duration of this post-activation depression and related H-reflex suppression (seconds) was similar to rate-dependent depression that is also due to post-activation depression. We conclude that extensor H-reflex inhibition by brief flexor afferent conditioning is produced by both post-activation depression of extensor Ia afferents and long-lasting inhibition of extensor motoneurons, rather than from PAD inhibiting Ia afferent terminals. KEY POINTS: Suppression of extensor H-reflexes by flexor afferent conditioning was thought to be mediated by GABAA receptor-mediated primary afferent depolarization (PAD) shunting action potentials in the Ia afferent terminal. In line with recent findings that PAD has a facilitatory role in Ia afferent conduction, we show here that when large enough, PAD can evoke orthodromic spikes that travel to the Ia afferent terminal to evoke EPSPs in the motoneuron. These PAD-evoked spikes also produce post-activation depression of Ia afferent terminals and may mediate the short- and long-lasting suppression of extensor H-reflexes in response to flexor afferent conditioning. Our findings highlight that we must re-examine how changes in the activation of GABAergic interneurons and PAD following nervous system injury or disease affects the regulation of Ia afferent transmission to spinal neurons and ultimately motor dysfunction in these disorders.
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Affiliation(s)
- Krista Metz
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Isabel Concha Matos
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Krishnapriya Hari
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Omayma Bseis
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Babak Afsharipour
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Shihao Lin
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Rahul Singla
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Keith K Fenrich
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Yaqing Li
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - David J Bennett
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
| | - Monica A Gorassini
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
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Metz K, Matos IC, Li Y, Afsharipour B, Thompson CK, Negro F, Quinlan KA, Bennett DJ, Gorassini MA. Facilitation of sensory transmission to motoneurons during cortical or sensory-evoked primary afferent depolarization (PAD) in humans. J Physiol 2023; 601:1897-1924. [PMID: 36916205 PMCID: PMC11037101 DOI: 10.1113/jp284275] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Accepted: 03/09/2023] [Indexed: 03/16/2023] Open
Abstract
Sensory and corticospinal tract (CST) pathways activate spinal GABAergic interneurons that have axoaxonic connections onto proprioceptive (Ia) afferents that cause long-lasting depolarizations (termed primary afferent depolarization, PAD). In rodents, sensory-evoked PAD is produced by GABAA receptors at nodes of Ranvier in Ia afferents, rather than at presynaptic terminals, and facilitates spike propagation to motoneurons by preventing branch-point failures, rather than causing presynaptic inhibition. We examined in 40 human participants whether putative activation of Ia-PAD by sensory or CST pathways can also facilitate Ia afferent activation of motoneurons via the H-reflex. H-reflexes in several leg muscles were facilitated by prior conditioning from low-threshold proprioceptive, cutaneous or CST pathways, with a similar long-lasting time course (∼200 ms) to phasic PAD measured in rodent Ia afferents. Long trains of cutaneous or proprioceptive afferent conditioning produced longer-lasting facilitation of the H-reflex for up to 2 min, consistent with tonic PAD in rodent Ia afferents mediated by nodal α5-GABAA receptors for similar stimulation trains. Facilitation of H-reflexes by this conditioning was likely not mediated by direct facilitation of the motoneurons because isolated stimulation of sensory or CST pathways did not alone facilitate the tonic firing rate of motor units. Furthermore, cutaneous conditioning increased the firing probability of single motor units (motoneurons) during the H-reflex without increasing their firing rate at this time, indicating that the underlying excitatory postsynaptic potential was more probable, but not larger. These results are consistent with sensory and CST pathways activating nodal GABAA receptors that reduce intermittent failure of action potentials propagating into Ia afferent branches. KEY POINTS: Controlled execution of posture and movement requires continually adjusted feedback from peripheral sensory pathways, especially those that carry proprioceptive information about body position, movement and effort. It was previously thought that the flow of proprioceptive feedback from Ia afferents was only reduced by GABAergic neurons in the spinal cord that sent axoaxonic projections to the terminal endings of sensory axons (termed GABAaxo neurons). Based on new findings in rodents, we provide complementary evidence in humans to suggest that sensory and corticospinal pathways known to activate GABAaxo neurons that project to dorsal parts of the Ia afferent also increase the flow of proprioceptive feedback to motoneurons in the spinal cord. These findings support a new role for spinal GABAaxo neurons in facilitating afferent feedback to the spinal cord during voluntary or reflexive movements.
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Affiliation(s)
- Krista Metz
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Isabel Concha Matos
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Yaqing Li
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Babak Afsharipour
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | | | - Francesco Negro
- Clinical and Experimental Sciences, Universita degli Studi di Brescia, Brescia, Italy
| | - Katharina A Quinlan
- George and Anne Ryan Institute for Neuroscience, Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, USA
| | - David J Bennett
- Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
| | - Monica A Gorassini
- Biomedical Engineering, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Canada
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Pethő B, Szilágyi GB, Mengyel B, Nagy T, Farkas F, Kátai-Fadgyas K, Volk B. Development and Process Intensification of an Efficient Flow–Cascade Reaction Sequence in the Synthesis of Afizagabar. Org Process Res Dev 2022. [DOI: 10.1021/acs.oprd.1c00481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Bálint Pethő
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Gábor B. Szilágyi
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Béla Mengyel
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Tamás Nagy
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Ferenc Farkas
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Katalin Kátai-Fadgyas
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
| | - Balázs Volk
- Directorate of Drug Substance Development, Egis Pharmaceuticals Plc., P.O. Box 100, H-1475 Budapest, Hungary
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Lebrun F, Violle N, Letourneur A, Muller C, Fischer N, Levilly A, Orset C, Sors A, Vivien D. Post-acute delivery of α5-GABAA antagonist, S 44819, improves functional recovery in juvenile rats following stroke. Exp Neurol 2021; 347:113881. [PMID: 34597681 DOI: 10.1016/j.expneurol.2021.113881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 09/21/2021] [Accepted: 09/24/2021] [Indexed: 11/04/2022]
Abstract
Hypo-excitability was reported in the peri-infarct tissue following stroke, an effect counteracted by a blockage of α5-GABAA receptors in adult rodents. Our present study aims to evaluate the effect of a selective α5-GABAA receptor antagonist, S 44819, in stroke in juvenile animals. We have set up and characterized an original model of transient ischemic stroke in 28 day-old Sprague-Dawley rats (45-min occlusion of the middle cerebral artery by intraluminal suture). In this model, S 44819 (1, 3 and 10 mg/kg, b.i.d) was orally administered from day 3 to day 16 after stroke onset. Sensorimotor recovery was assessed on day 1, day 9 and day 16 after stroke onset. Results show that rats treated with S 44819 at the doses of 3 and 10 mg/kg displayed a significant improvement of the neurological deficits (neuroscore) on day 9 and day 16, when compared with animals treated with vehicle. Grip-test data analysis reveals that rats treated with S 44819 at the dose of 3 mg/kg displayed a better recovery on day 9 and day 16. These results are in agreement with those previously observed in adult rats, demonstrating that targeting α5-GABAA receptors improves neurological recovery after stroke in juvenile rats.
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Affiliation(s)
- Florent Lebrun
- ETAP-Lab, STROK@LLIANCE, 13 Rue du Bois de la Champelle, 54500 Vandoeuvre-les-Nancy, France; Normandie Univ, UNICAEN, INSERM, GIP Cyceron, Institut Blood and Brain @Caen-Normandie (BB@C), UMR-S U1237, Physiopathology and Imaging of Neurological Disorders (PhIND), Caen, France
| | - Nicolas Violle
- ETAP-Lab, STROK@LLIANCE, 13 Rue du Bois de la Champelle, 54500 Vandoeuvre-les-Nancy, France
| | - Annelise Letourneur
- ETAP-Lab, STROK@LLIANCE, 13 Rue du Bois de la Champelle, 54500 Vandoeuvre-les-Nancy, France
| | - Christophe Muller
- ETAP-Lab, STROK@LLIANCE, 13 Rue du Bois de la Champelle, 54500 Vandoeuvre-les-Nancy, France
| | - Nicolas Fischer
- ETAP-Lab, STROK@LLIANCE, 13 Rue du Bois de la Champelle, 54500 Vandoeuvre-les-Nancy, France
| | - Anthony Levilly
- ESRP (European Stroke Research Platform), Centre Universitaire de Ressources Biologiques (CURB), Université Caen Basse Normandie, Caen, France
| | - Cyrille Orset
- Normandie Univ, UNICAEN, INSERM, GIP Cyceron, Institut Blood and Brain @Caen-Normandie (BB@C), UMR-S U1237, Physiopathology and Imaging of Neurological Disorders (PhIND), Caen, France; ESRP (European Stroke Research Platform), Centre Universitaire de Ressources Biologiques (CURB), Université Caen Basse Normandie, Caen, France
| | - Aurore Sors
- Institut de Recherches Internationales Servier, Suresnes, France
| | - Denis Vivien
- Normandie Univ, UNICAEN, INSERM, GIP Cyceron, Institut Blood and Brain @Caen-Normandie (BB@C), UMR-S U1237, Physiopathology and Imaging of Neurological Disorders (PhIND), Caen, France; Department of Clinical Research, CHU Caen-Normandie, Caen, France.
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Regenhardt RW, Takase H, Lo EH, Lin DJ. Translating concepts of neural repair after stroke: Structural and functional targets for recovery. Restor Neurol Neurosci 2020; 38:67-92. [PMID: 31929129 PMCID: PMC7442117 DOI: 10.3233/rnn-190978] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Stroke is among the most common causes of adult disability worldwide, and its disease burden is shifting towards that of a long-term condition. Therefore, the development of approaches to enhance recovery and augment neural repair after stroke will be critical. Recovery after stroke involves complex interrelated systems of neural repair. There are changes in both structure (at the molecular, cellular, and tissue levels) and function (in terms of excitability, cortical maps, and networks) that occur spontaneously within the brain. Several approaches to augment neural repair through enhancing these changes are under study. These include identifying novel drug targets, implementing rehabilitation strategies, and developing new neurotechnologies. Each of these approaches has its own array of different proposed mechanisms. Current investigation has emphasized both cellular and circuit-based targets in both gray and white matter, including axon sprouting, dendritic branching, neurogenesis, axon preservation, remyelination, blood brain barrier integrity, blockade of extracellular inhibitory signals, alteration of excitability, and promotion of new brain cortical maps and networks. Herein, we review for clinicians recovery after stroke, basic elements of spontaneous neural repair, and ongoing work to augment neural repair. Future study requires alignment of basic, translational, and clinical research. The field continues to grow while becoming more clearly defined. As thrombolysis changed stroke care in the 1990 s and thrombectomy in the 2010 s, the augmentation of neural repair and recovery after stroke may revolutionize care for these patients in the coming decade.
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Affiliation(s)
- Robert W Regenhardt
- Department of Neurology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
| | - Hajime Takase
- Department of Neurology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
- Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
| | - Eng H Lo
- Department of Neurology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
- Department of Radiology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
| | - David J Lin
- Department of Neurology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
- Center for Neurotechnology and Neurorecovery, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114
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