Quantitative assessment of the motor-sensory specificity of the motor and primary sensory neurons after the end-to-side neurorrhaphy

Abstract

We sought to evaluate the motor-sensory specificity of the motor and primary sensory neurons after the end-to-side neurorrhaphy. We divided 90 rats into three groups: (1) end-to-side neurorrhaphy using the ulnar nerve as donor nerve and the musculocutaneous nerve as recipient nerve; (2) normal control; and (3) transected nerve with the stumps buried. At 5 months, we monitored the grooming test, the electromyographic recordings, the histologic changes in the nerve, and quantitatively evaluated motoneurons and dorsal root ganglion (DRG) neurons following their retrograde labeling by Fluoro-Gold (Sigma, St. Louis, MO) applied to the musculocutaneous nerve and its biceps brachii branch. Grooming and electrophysiological investigations recovered successfully in the end-to-side group. The implanted musculocutaneous nerve contained varying but satisfactory numbers of axons. In the end-to-side group, the proportion of motoneurons for the biceps brachii branch of musculocutaneous nerve was very similar to the musculocutaneous nerve sections proximal to this branch (17.3% ± 2.7% and 21.7% ± 3.7%, respectively), but it did not correspond with the proportion of the biceps brachii branch of musculocutaneous nerve in the normal group (28.3% ± 3.5%). The present study confirms that limited but functional reinnervation can occur after the end-to-side neurorrhaphy, and the motor-sensory specificity is not important.