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. 2017 Dec;56(6):1149-1154.
doi: 10.1002/mus.25590. Epub 2017 Mar 21.

Median and ulnar nerve injuries reduce volitional forelimb strength in rats

Eric C Meyers  1   2 , Rafael Granja  1   2 , Bleyda R Solorzano  1 , Mario Romero-Ortega  1   2 , Michael P Kilgard  1   3 , Robert L Rennaker 2nd  1   2   3 , Seth Hays  1   2
Affiliations

Median and ulnar nerve injuries reduce volitional forelimb strength in rats

Eric C Meyers et al. Muscle Nerve. 2017 Dec.

Abstract

Introduction: Peripheral nerve injuries (PNI) are among the leading causes of physical disability in the United States. The majority of injuries occur in the upper extremities, and functional recovery is often limited. Robust animal models are critical first steps for developing effective therapies to restore function after PNI.

Methods: We developed an automated behavioral assay that provides quantitative measurements of volitional forelimb strength in rats. Multiple forelimb PNI models involving the median and ulnar nerves were used to assess forelimb function for up to 13 weeks postinjury.

Results: Despite multiple weeks of task-oriented training following injury, rats exhibit significant reductions in multiple quantitative parameters of forelimb function, including maximal pull force and speed of force generation.

Discussion: This study demonstrates that the isometric pull task is an effective method of evaluating forelimb function following PNI and may aid in development of therapeutic interventions to restore function. Muscle Nerve 56: 1149-1154, 2017.

Keywords: behavior; forelimb; nerve transection; peripheral nerve injury; rat; volitional strength.

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Conflict of interest statement

Conflicts of Interest: R.L.R. own shares in Vulintus, Inc., which is developing products based on this research. Vulintus, Inc., did not have any role in data collection, analysis, or the decision to publish. The remaining authors have no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Isometric pull task and experimental design. (A) An animal performing the isometric pull task by firmly grasping and pulling on the handle. (B) Maximal pull force of individual trials taken from a behavioral session. Each point represents the maximal pull force of a single trial, with dark gray points indicating successful trials and light gray ones indicating unsuccessful trials. The black line indicates the adaptive threshold, and the dashed black line indicates the maximum threshold (120 grams). (C) Timeline of experiment.
FIGURE 2
FIGURE 2
Multiple PNI models resulted in varying degrees of transient and chronic impairments in metrics of forelimb function. Maximal pull force (A), success rate (B), and maximal pull speed (C) each show varying degrees of impairment dependent on lesion. (D) Animals performed several hundred trials per day across groups, with no reduction in trials performed following lesion. All plots show group averages, and error bars indicate ± SEM. *P < 0.0083 for the distal group, †P < 0.0083 for the proximal group, ◆P < 0.0071 for the proximal gap group for each time point compared with prelesion levels in panels A–C.
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