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Functional organization of locomotor interneurons in the ventral lumbar spinal cord of the newborn rat.

Antri M, Mellen N, Cazalets JR - PLoS ONE (2011)

Bottom Line: Moreover, L1 segment lesioning induced the most important changes in the locomotor activity in comparison with lesions at the T13 or L2 segments.However, no lesions led to selective disruption of either flexor or extensor output.In addition, this study found no evidence of functional parcellation of locomotor interneurons into flexor and extensor pools at the dorsal-ventral midline of the lumbar spinal cord of the rat.

View Article: PubMed Central - PubMed

Affiliation: Université de Bordeaux, Centre National de la Recherche Scientifique, Institut des Neurosciences Cognitives et Intégratives d'Aquitaine, Unité Mixte de Recherche 5287, Bordeaux, France. myriam.antri@gmail.com

ABSTRACT
Although the mammalian locomotor CPG has been localized to the lumbar spinal cord, the functional-anatomical organization of flexor and extensor interneurons has not been characterized. Here, we tested the hypothesis that flexor and extensor interneuronal networks for walking are physically segregated in the lumbar spinal cord. For this purpose, we performed optical recordings and lesion experiments from a horizontally sectioned lumbar spinal cord isolated from neonate rats. This ventral hemi spinal cord preparation produces well-organized fictive locomotion when superfused with 5-HT/NMDA. The dorsal surface of the preparation was visualized using the Ca(2+) indicator fluo-4 AM, while simultaneously monitoring motor output at ventral roots L2 and L5. Using calcium imaging, we provided a general mapping view of the interneurons that maintained a stable phase relationship with motor output. We showed that the dorsal surface of L1 segment contains a higher density of locomotor rhythmic cells than the other segments. Moreover, L1 segment lesioning induced the most important changes in the locomotor activity in comparison with lesions at the T13 or L2 segments. However, no lesions led to selective disruption of either flexor or extensor output. In addition, this study found no evidence of functional parcellation of locomotor interneurons into flexor and extensor pools at the dorsal-ventral midline of the lumbar spinal cord of the rat.

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Experimental setup.A, Schematic drawing of the in vitro ventral SC preparation with VRs recording electrodes positioned at L2 and L5 (r = right; l = left). B, Transverse section of an intact SC (B1) and of two SC preparations with a horizontal cut at different dorso-ventral levels (B2, B3). Scale bars = 300 µm. The bottom panels show the motor activity recorded in VRs. F = Flexor activity, E = Extensor activity. C, Schematic drawing of transverse sections of the SC illustrating horizontal cuts at different levels (light grey bar and dark grey bar). The histogram plots the data of the mean period ± SEM of the different horizontal cuts.
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pone-0020529-g001: Experimental setup.A, Schematic drawing of the in vitro ventral SC preparation with VRs recording electrodes positioned at L2 and L5 (r = right; l = left). B, Transverse section of an intact SC (B1) and of two SC preparations with a horizontal cut at different dorso-ventral levels (B2, B3). Scale bars = 300 µm. The bottom panels show the motor activity recorded in VRs. F = Flexor activity, E = Extensor activity. C, Schematic drawing of transverse sections of the SC illustrating horizontal cuts at different levels (light grey bar and dark grey bar). The histogram plots the data of the mean period ± SEM of the different horizontal cuts.

Mentions: All procedures were approved by the Animal Care and Use Committee at the University of Bordeaux and conform to the guidelines of the European Community Council (86/609/EEC). Experiments were carried out on P1 to P4 Wistar rats of both sexes (n = 88). Animals were anaesthetized by hypothermia, decapitated, eviscerated and transferred to a solution of oxygenated cold artificial cerebrospinal fluid (aCSF; pH: 7.4) of the following composition (in mM): NaCl:130, NAH2PO4:0.58, MgSO4:1.3, CaCl2:2.5, NaHCO3:25, D-Glucose:10, KCl:3. The experimental procedure has previously been described [22], [23]. Briefly, SCs with ventral roots (VRs) were dissected, affixed dorsal side up to a block of Sylgard (Dow-Corning, USA) and transferred to the stage of a vibratome. The cords were sectioned horizontally up to the central canal (Figure 1A). The preparation was then placed dorsal side up in the recording chamber.


Functional organization of locomotor interneurons in the ventral lumbar spinal cord of the newborn rat.

Antri M, Mellen N, Cazalets JR - PLoS ONE (2011)

Experimental setup.A, Schematic drawing of the in vitro ventral SC preparation with VRs recording electrodes positioned at L2 and L5 (r = right; l = left). B, Transverse section of an intact SC (B1) and of two SC preparations with a horizontal cut at different dorso-ventral levels (B2, B3). Scale bars = 300 µm. The bottom panels show the motor activity recorded in VRs. F = Flexor activity, E = Extensor activity. C, Schematic drawing of transverse sections of the SC illustrating horizontal cuts at different levels (light grey bar and dark grey bar). The histogram plots the data of the mean period ± SEM of the different horizontal cuts.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3117791&req=5

pone-0020529-g001: Experimental setup.A, Schematic drawing of the in vitro ventral SC preparation with VRs recording electrodes positioned at L2 and L5 (r = right; l = left). B, Transverse section of an intact SC (B1) and of two SC preparations with a horizontal cut at different dorso-ventral levels (B2, B3). Scale bars = 300 µm. The bottom panels show the motor activity recorded in VRs. F = Flexor activity, E = Extensor activity. C, Schematic drawing of transverse sections of the SC illustrating horizontal cuts at different levels (light grey bar and dark grey bar). The histogram plots the data of the mean period ± SEM of the different horizontal cuts.
Mentions: All procedures were approved by the Animal Care and Use Committee at the University of Bordeaux and conform to the guidelines of the European Community Council (86/609/EEC). Experiments were carried out on P1 to P4 Wistar rats of both sexes (n = 88). Animals were anaesthetized by hypothermia, decapitated, eviscerated and transferred to a solution of oxygenated cold artificial cerebrospinal fluid (aCSF; pH: 7.4) of the following composition (in mM): NaCl:130, NAH2PO4:0.58, MgSO4:1.3, CaCl2:2.5, NaHCO3:25, D-Glucose:10, KCl:3. The experimental procedure has previously been described [22], [23]. Briefly, SCs with ventral roots (VRs) were dissected, affixed dorsal side up to a block of Sylgard (Dow-Corning, USA) and transferred to the stage of a vibratome. The cords were sectioned horizontally up to the central canal (Figure 1A). The preparation was then placed dorsal side up in the recording chamber.

Bottom Line: Moreover, L1 segment lesioning induced the most important changes in the locomotor activity in comparison with lesions at the T13 or L2 segments.However, no lesions led to selective disruption of either flexor or extensor output.In addition, this study found no evidence of functional parcellation of locomotor interneurons into flexor and extensor pools at the dorsal-ventral midline of the lumbar spinal cord of the rat.

View Article: PubMed Central - PubMed

Affiliation: Université de Bordeaux, Centre National de la Recherche Scientifique, Institut des Neurosciences Cognitives et Intégratives d'Aquitaine, Unité Mixte de Recherche 5287, Bordeaux, France. myriam.antri@gmail.com

ABSTRACT
Although the mammalian locomotor CPG has been localized to the lumbar spinal cord, the functional-anatomical organization of flexor and extensor interneurons has not been characterized. Here, we tested the hypothesis that flexor and extensor interneuronal networks for walking are physically segregated in the lumbar spinal cord. For this purpose, we performed optical recordings and lesion experiments from a horizontally sectioned lumbar spinal cord isolated from neonate rats. This ventral hemi spinal cord preparation produces well-organized fictive locomotion when superfused with 5-HT/NMDA. The dorsal surface of the preparation was visualized using the Ca(2+) indicator fluo-4 AM, while simultaneously monitoring motor output at ventral roots L2 and L5. Using calcium imaging, we provided a general mapping view of the interneurons that maintained a stable phase relationship with motor output. We showed that the dorsal surface of L1 segment contains a higher density of locomotor rhythmic cells than the other segments. Moreover, L1 segment lesioning induced the most important changes in the locomotor activity in comparison with lesions at the T13 or L2 segments. However, no lesions led to selective disruption of either flexor or extensor output. In addition, this study found no evidence of functional parcellation of locomotor interneurons into flexor and extensor pools at the dorsal-ventral midline of the lumbar spinal cord of the rat.

Show MeSH
Related in: MedlinePlus