The Ex vivo Preparation of Spinal Cord Slice for the Whole-Cell Patch-Clamp Recording in Motor Neurons During Spinal Cord Stimulation

Summary

This protocol describes a method using a patch-clamp to study the electrical responses of motor neurons to spinal cord stimulation (SCS) with high spatiotemporal resolution, which can help researchers improve their skills in separating the spinal cord and maintaining cell viability simultaneously.

Abstract

Spinal cord stimulation (SCS) can effectively restore locomotor function after spinal cord injury (SCI). Because the motor neurons are the final unit to execute sensorimotor behaviors, directly studying the electrical responses of motor neurons with SCS can help us understand the underlying logic of spinal motor modulation. To simultaneously record diverse stimulus characteristics and cellular responses, a patch-clamp is a good method to study the electrophysiological characteristics at a single-cell scale. However, there are still some complex difficulties in achieving this goal, including maintaining cell viability, quickly separating the spinal cord from the bony structure, and using the SCS to successfully induce action potentials. Here, we present a detailed protocol using patch-clamp to study the electrical responses of motor neurons to SCS with high spatiotemporal resolution, which can help researcher improve their skills in separating the spinal cord and maintaining the cell viability at the same time to smoothly study the electrical mechanism of SCS on motor neuron and avoid unnecessary trial and mistake.

Introduction

Spinal cord stimulation (SCS) can effectively restore locomotor function after spinal cord injury (SCI). Andreas Rowald et al. reported that SCS enables lower limb locomotor and trunk function within a single day¹. Exploring the biological mechanism of SCS for locomotor recovery is a critical and trending research field for developing a more precise SCS strategy. For example, Grégoire Courtine's team demonstrated that excitatory Vsx2 interneuron and Hoxa10 neurons in the spinal cord are the key neurons to response to SCS, and cell-specific neuromodulation is feasible to restore the rat walking ability after SCI²....

Protocol

The Institutional Animal Care and Use Committee approved all animal experiments and the studies were conducted in accordance with relevant animal welfare regulations.

1. Animals preparation

1. Animals
   1. Housing information: House male Sprague-Dawley rats (Postnatal 10-14 days, P10-P14) in a specific pathogen-free environment.
      NOTE: Room conditions were maintained at 20 °C ± 2 °C, humidity: 50%-60%, with a 12-h light/ dark cycle. Animals had free access to food and water.
   2. Label the motor neurons retrogradely: Inject Fluoro-Gold (FG) into the bilateral tibialis anterio....

Results

Thanks to the rigorous low-temperature maintenance during the fine operation (Supplementary Figure 1, Supplementary Figure 2, and Figure 1), the cell viability was good enough to perform subsequent electrophysiological recordings. To simulate the clinical scenario as much as possible, we used micromanipulation to place the SCS cathode and anode near the dorsal midline and DREZ, respectively (Figure 2), which could initiate neural signal in .......

Discussion

The movement information modulated by SCS is finally converged to the motor neurons. Therefore, taking the motor neurons as the research target may simplify the study design and reveal the neuromodulation mechanism of SCS more directly. To simultaneously record diverse stimulus characteristics and cellular responses, a patch-clamp is a good method to study the electrophysiological characteristics at a single-cell scale. However, there are still some difficulties, including how to maintain cell viability, how to quickly s.......

Materials

Name	Company	Catalog Number	Comments
Adenosine 5’-triphosphate magnesium salt	Sigma	A9187
Ascorbic Acid	Sigma	A4034
CaCl2·2H2O	Sigma	C5080
Choline Chloride	Sigma	C7527
Cover slide tweezers	VETUS	36A-SA	Clip a slice
D-Glucose	Sigma	G8270
EGTA	Sigma	E4378
Fine scissors	RWD Life Science	S12006-10	Cut the diaphragm
Fluorescence Light Source	Olympus	U-HGLGPS
Fluoro-Gold	Fluorochrome	Fluorochrome	Label the motor neuron
Guanosine 5′-triphosphate sodium salt hydrate	Sigma	G8877
HEPES	Sigma	H3375
infrared CCD camera	Dage-MTI	IR-1000E
KCl	Sigma	P5405
K-gluconate	Sigma	P1847
Low melting point agarose	Sigma	A9414
MgSO4·7H2O	Sigma	M2773
Micromanipulator	Sutter Instrument	MP-200
Micropipette puller	Sutter instrument	P1000
Micro-scissors	Jinzhong	wa1020	Laminectomy
Microscope for anatomy	Olympus	SZX10
Microscope for ecletrophysiology	Olympus	BX51WI
Micro-toothed tweezers	RWD Life Science	F11008-09	Lift the cut vertebral body
NaCl	Sigma	S5886
NaH2PO4	Sigma	S8282
NaHCO3	Sigma	V900182
Na-Phosphocreatine	Sigma	P7936
Objective lens for ecletrophysiology	Olympus	LUMPLFLN60XW	working distance 2 mm
Osmometer	Advanced	FISKE 210
Patch-clamp amplifier	Axon	Multiclamp 700B
Patch-clamp digitizer	Axon	Digidata 1550B
pH meter	Mettler Toledo	FE28
Slice Anchor	Multichannel system	SHD-27H
Spinal cord stimulatior	PINS	T901
Toothed tweezer	RWD Life Science	F13030-10	Lift the xiphoid
Vibratome	Leica	VT1200S
Wide band ultraviolet excitation filter	Olympus	U-MF2