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* These authors contributed equally
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.
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.
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....
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.......
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.......
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.......
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.
....Name | Company | Catalog Number | Comments |
Absorbent underpad | VWR | 115-0684 | |
AD converter | Cambridge Electronic Design, UK | CED 1401micro | |
Amplifier | Workshop Zoological Institute, UoC | - | |
Digital stimulator | Workshop Zoological Institute, UoC | MS 501 | |
EMG electrodes | Workshop Zoological Institute, UoC | Two twisted, insulated copper wires (50 µm outer diameter) were soldered to a male plug and connected to a differential amplifier. | |
Eye ointment | Bayer | Bepanthen | |
Glass pipette | Workshop Zoological Institute, UoC | - | Prepare a glass pipette bent into a simple glass hook in the flame of a Bunsen burner. |
Heating box | MediHeat | MediHeat V1200 | |
Heating pad | WPI | 61840 Heating pad | |
Hook electrodes | Workshop 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. |
Ketamine | Pfizer | Ketavet | |
Rectal probe | WPI | RET-3 | |
Stimulator isolation unit | Workshop Zoological Institute, UoC | MI 401 | |
Sterilizer | CellPoint Scientific | Germinator 500 | Routine 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 controller | WPI | ATC200 | |
Vaseline | Bayer | - | |
Xylazine | Bayer | Rompun |
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