Neurotropism following end-to-side neurorrhaphy by neuron retrograde tracing technique

Objective To detect whether there is neurotropism following end-to-side neurorrhaphy by means of the neuron retrograde tracing technique. Methods Forty female Sprague-Dawley rats were randomly divided into 4 groups: tracing main branch of musculcutaneous nerve(MC) of end-to-side group, tracing MC main branch of normal group, tracing MC motor branch of end-to-side group and tracing MC motor branch of normal group.In two end-to-side groups, the MC was transeeted, then an 1 mm epineukral window was created on the ulnar nerve. Distal end of MC nerve was sutured to the windowed ulnar nerve by means of end-to-side neurorrhaphy.In two normal control groups, MC and ulnar nerves were just exposed. Five months post operation, by means of retrograde Fluoro-Gold neuron tracing technique,the number of C5～ T1 anterior horn motoneurons and dorsal root ganglion sensory neurons of all groups were counted. Results In two tracing MC main branch groups: the motor neuron counts in end-to-side group was 245.2 ± 93.8, the motor neuron counts in normal group was 846.7 ± 264.8, and counts of end-to-side group was 30.0% of the normal control group (P＜ 0.01). The sensory neuron counts in end-to-side was 434.7 ± 160.4, the sensory neuron counts in normal group was 1545.2 ± 287.4, and counts of end-to-side group was 28.1% of the normal control group (P ＜ 0.01). The per-centage of motor neuron in end-to-side group was 0.36 ± 0.09, there was no difference between end-to-side group and normal control group(P＞ 0.05). In two tracing MC motor branch groups: the motor neuron counts in end-to-side group was 72.3 ± 35.3, the motor neuron counts in normal group was 189.7 ± 57.0, and counts of end-to-side group was 38.1% of the normal control group (P ＜ 0.01). The sensory neuron counts in end-to-side was 110.8 ± 52.5, the sensory neuron counts in normal group was 157.9 ± 50.0, and counts of end-to-side group was 70.2% of the normal control group (P ＞ 0.05). The percentage of motor neuron in end-to-side group was 0.40 ± 0.14, the difference between end-to-side group and normal control group was signifieant(P ＜ 0.01 ). Conclusion Neurotropism in collateral spouting after end-to-side neurorrhaphy is not significant. Key words: Peripheral nerve;  End-to-side neuroraphy;  Neurons;  Neurotropisn ;  Spinal cord;  Dorsal root ganglion