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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

The clinical evaluation of spasticity based on the Hoffmann reflex (H-reflex) and using electrical stimulation of peripheral nerves is an established method. Here, we provide a protocol for a terminal and direct nerve stimulation for H-reflex quantification in the mouse forepaw.

Abstract

The Hoffmann reflex (H-reflex), as an electrical analog to the stretch reflex, allows electrophysiological validation of the integrity of neural circuits after injuries such as spinal cord damage or stroke. An increase of the H-reflex response, together with symptoms like non-voluntary muscle contractions, pathologically augmented stretch reflex, and hypertonia in the corresponding muscle, is an indicator of post-stroke spasticity (PSS).

In contrast to rather nerve-unspecific transcutaneous measurements, here, we present a protocol to quantify the H-reflex directly at the ulnar and median nerves of the forepaw, which is applicable, with minor modifications, to the tibial and sciatic nerve of the hindpaw. Based on the direct stimulation and the adaptation to different nerves, the method represents a reliable and versatile tool to validate electrophysiological changes in spasticity-related disease models.

Introduction

The Hoffmann reflex (H-reflex), named after the physiologist Paul Hoffmann, can be evoked by electrical stimulation of peripheral nerves, which carry axons of sensory and motor neurons arising from and leading to the same muscles. It is the electrically induced analog of the monosynaptic stretch reflex, and shares the same pathway1. Unlike the muscle stretch, the H-reflex results from electrical stimulation. When peripheral nerves are electrically stimulated at low current intensity, the Ia afferent fibers are typically depolarized first due to their large axon diameter2. Their action potentials excite alpha motorne....

Protocol

All experiments were conducted in compliance with European and National animal care laws and institutional guidelines, and were approved by the Landesamt für Natur-, Umwelt-, und Verbraucherschutz North Rhine-Westphalia (Az: 81-02.04.2019.A309). The protocol is optimized for adult mice (approx. 8-16 weeks old C57Bl/6J mice) and the forelimb recording. It can be easily adapted by stimulating the respective nerves of the hindlimb and recording hindpaw muscles (Figure 1B). A descripti.......

Representative Results

From the n = 15 stimulation trials per stimulation frequency and paw, select at least n = 10 successful recordings for the analysis. Trials with measurement errors (e.g., missing M-wave) are excluded from the analysis. Analyze each trial separately and generate an average for group/time comparisons later on. The latency between stimulation and appearance of the M-wave and H-wave is recorded for each trial. In our experience, the M-wave occurs approximately 2 ms after stimulation, and the H-wave after 6-8 ms, due to the l.......

Discussion

In contrast to previously described transcutaneous H-reflex measurements in the mouse6, we provide a more direct and nerve-specific measurement. This new approach can be applied to the nerves of the fore- and hindlimb (e.g., the median, ulnar, and radial nerves, and the tibial, and sciatic nerves, respectively), rendering this method adaptable as a diagnostic tool to many disease models (e.g., stroke, multiple sclerosis, amyotrophic lateral sclerosis, traumatic brain injury, and spinal cord injury.......

Acknowledgements

The authors gratefully acknowledge support by T. Akay, Dalhousie University, during a visit of MG to his lab. This work was supported by funding from the Friebe Foundation (T0498/28960/16) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Project-ID 431549029 - SFB 1451.

....

Materials

NameCompanyCatalog NumberComments
Absorbent underpadVWR115-0684
AD converterCambridge Electronic Design, UKCED 1401micro
AmplifierWorkshop Zoological Institute, UoC-
Digital stimulatorWorkshop Zoological Institute, UoCMS 501
EMG electrodesWorkshop Zoological Institute, UoCTwo twisted, insulated copper wires (50 µm outer diameter) were soldered to a male plug and connected to a differential amplifier.
Eye ointmentBayerBepanthen
Glass pipetteWorkshop Zoological Institute, UoC-Prepare a glass pipette bent into a simple glass hook in the flame of a Bunsen burner.
Heating boxMediHeatMediHeat V1200
Heating padWPI61840 Heating pad
Hook electrodesWorkshop Zoological Institute, UoC-To produce the electrodes, bend stainless steel miniature pins into hooks at one end and insert into blunt cannulas to create direct mechanical contact. Solder the end of the cannula to copper wires (length approx. 50 cm), which are connected to either stimulation or recording device.
KetaminePfizerKetavet
Rectal probeWPIRET-3
Stimulator isolation unitWorkshop Zoological Institute, UoCMI 401
SterilizerCellPoint ScientificGerminator 500Routine pre- and post-operative disinfection of the surgical equipment should be done by heat sterilization. Decontaminate instruments for 15 s in the heated glass bead bath (260°C).
Temperature controllerWPIATC200
VaselineBayer-
XylazineBayerRompun

References

  1. Palmieri, R. M., Ingersoll, C. D., Hoffman, M. A. The Hoffmann reflex: methodologic considerations and applications for use in sports medicine and athletic training research. Journal of Athletic Training. 39 (3), 268-277 (2004).
  2. Henneman, E., Somjen, G., Carpenter, D. O.

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