| Part One Effect of different management of C7 nerve root on corticospinal neurons: an experimental studyObjective: To study the distribution of the corticospinal neurons of C7 nerve root in the rat motor cortex, and the effect of different management of C7 nerve root on corticospinal neurons, to provide foundation for further research about the cortex plasticity following C7 nerve transfer.Methods: Neuronal tracing technique was used, and the 4%WGA-HRP tracer was injected at the C5,C6,C7,C8,T1 and C5,6,7,8,T1 cervical spinal cord segment respectively. The animals survived 48-72 hours, and were killed by transcardial perfusion of 1.25% glutaraldehyde and 1.0% paraformaldehyde in phosphate buffer (PH=7.4), then the brain and spinal cord were sectioned coronally at 50-jam thickness on a freezing microtome serially. The sections were reacted for presence of HRP by using TMB kit, and counterstained with 1% neutral red, then under the microscope to observe the distribution range and the morphology properties of corticospinal neurons of C7 nerve root in the motor cortex. And the model of the C7 transected was established with different style: anterior division, posterior division and middle trunk, then subdivided into 5 time groups, 1, 2, 4, 12, 24weeks. The grasping test was used to estimate the effect of different management of C7 root on the function of the forelimb. The tracer of 4% WGA-HRP was injected at the C7 spinal cord segment, After survived 48-72 hours, the animals were killed by transcardial perfusion, after perfusion, brain and spinal cord were immediately removed and immersed in 30% phosphate-buffer sucrose overnight at 4癈. The brains were then sectioned coronally at 50-um thickness on a freezing microtome serially. The sections were reacted for presence of HRP by using TMB kit, and counterstained with 1% neutral red, and then observe the changes of the distribution, counts, soma cross area, principal apical dendrite extension angle of 6 and basal dendrites of the corticospinal neurons with the image analysis system.Results The distribution of the corticospinal neurons of C5-T1 cervical spinal cord segment was segmental pattern, and the neurons of C7 nerve root are coniform or triangular and distributed at rostral of bregma of contralateral cortex from 2.5 to 1.5mm, that are situated in layer V of motor cortex (25%< Z<51%) Z = 39.69?.09; mean soma cross area was 1278?13um2, They had a principal apical dendrite and the angle of 9 was 6.8氨4.3? and several type of basal dendrites that mainly were first grade furcation, 446?8. Contrast with the normal group, there wasno significant difference (P>0.05) in the distribution, counts, soma cross area, principal apical dendrite extension angle of 0 of the corticospinal neurons after the different management of C7 nerve root, but the counts of the first grade furcation and multiple grade furcation were changed differently. Contrasted with the normal group there was significant difference (P<0.05)in the counts of the first grade furcation, but among them the counts were decreased at 2 weeks and stabled at 12 weeks after the posterior division and middle trunk transected; and decreased at 4 weeks and stabled at 24 weeks after anterior transected. Contrasted with the normal group there was significant difference (P<0.05)in the counts of the multiple grade furcation, but among them the counts were increased at 2 weeks and stabled at 12 weeks after the posterior division and middle trunk transected; and increased at 4 weeks and stabled at 24 weeks after anterior transected. Contrasted with the normal group, there was no significant difference (P>0.05) in the counts of the none furcation. And the ultrastructures of corticospinal neurons of C7 nerve root in the motor cortex were normal after the different management of C7 nerve root. Conclusion:1. The distribution pattern of the corticospinal neurons of C5-T1 cervical spinal cord segment was segmental.2. The neurons of C7 nerve root distributed at rostral of bregma of contralateral cortex from 2.5 to... |
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