The Study On The Applied Anatomy And Electrophysiology Of Canine Corticospinal Tract

Part I The Anatomical Observations and Measurements of Canine Spinal CordObjective: To observe the morphologic features and measure the applied anatomy data.Methods: Cross sections of canine spinal cord at each segment were prepared for histological evaluation using Nissl stain. The morphologic features of the spinal cord and its segments were observed. The transverse and sagittal diameters, cross-sectional area, gray and white area at each section were measured. The compression ratio, the ratio of the gray matter area to the cross-sectional area, and the ratio of the gray matter area to the white matter were calculated.Results: The canine spinal cord lies in the spinal tube, whose length is inconsistent with the spinal tube. The spinal cord are divided into approximately 36 segments, including 8 cervical (C), 13 thoracic (T), 7 lumbar (L), 3 sacral (S), and 5 coccygeal segments (Co). The anatomic relationship between spinal cord and vertebral body were as follows: C1-7 was at the same level of correlated vertebrae; C8 was at the level between C7-8 vertebrae; T1-6 level was one vertebra higher than the correlated vertebrae; T7-8 level was half vertebra higher than the correlated vertebrae; T9-L3 was at the same level of correlated vertebrae; L4-7 was at the level of L5-6 vertebrae; S1-Co5 was at the level of L6-7 vertebrae. In canine's spinal cord, there are two enlargements: cervical enlargement (C5-T1) and lumbar enlargement (L4-7). The variation tendency in spinal cord segments such as the transverse, sagittal diameters, grey and white matter areas were similar. There were more variations in transverse diameters than that of sagittal diameters at each segment. The largest transverse diameter segment of the spinal cord was C1, while the largest sagittal diameters segment was C6. Cross-sectional morphologic features, such as the ratio of grey matter area to white matter area, the ratio of the gray matter area to the cross-sectional area, the compression ratio, changed obviously at the different spinal cord levels, especially at the level of cervical and lumbar enlargements.Conclusions: Through measuring and calculating the characteristic parameters of spinal cord, such as the transverse and sagittal diameters, cross-sectional area, gray and white areas, the compression ratio, the ratio of the gray matter area to the cross-sectional area, and the ratio of the gray matter area to the white matter of each spinal cord segment, we provide the morphologic basis for the research on regeneration after spinal cord injury of canine.Part II Study on BDA Anterograde tracing and the Three Dimensional Reconstruction of Corticospinal Tract in Spinal Cord of CanineObjective: To provide the localization of corticospinal tract (CST) in spinal cord of canine with three-dimensional (3D) reconstruction technique. Methods: CST on the serial cross sections of the canine's spinal cord was located with BDA immune fluorescent anterograde tracing technique. The two-dimensional images were taken, registered, segmented and changed into gray-scale images under the Photoshop 7.0 circumstance. 3D-DOCTOR4.0 software was used to make 3D reconstruction of spinal cord, gray matter and bilateral CSTs.Results: 1. The pyramidal neuron and its axons were labeled with green fluorescence, and the green stripe-shaped pyramidal tract was observed. At the level of pyramid of medulla oblongata, green fluorescence labeled regions were distinct from the peripheral structures obviously. The signals labeled with green fluorescence crossed to the opposite side from central canal ventralis in decussation of pyramid, entered into the lateral funiculus, and then passed in the posterior part of lateral funiculus, accompanying with the posterior horn in cervical, thoracic, lumbar and sacral segments. At the level of T4 segment, the green labeled tracts were found in the posterior horn zone, and became smaller gradually. At the level of sacral segments, there were only little positive labeled tracts left. 2. The spinal cord and the CSTs can be reconstructed , observed and measured with 3D-DOCTOR software.Conclusions: 1. Through BDA-Streptavidin- FITC anterograde tracing technique, the canine CST can be located. 2. The canine CST originates from motor cortex, passing into the opposite lateral funiculus in spinal cord through pyramid decussation, and then accompanied with the posterior horn of gray matter downwards to sacral segment. 3. The spinal cord and the CSTs of canine can be reconstructed, observed and measured using 3D-DOCTOR software. Part III Preliminary Analysis on Electrophysiological Signals of Canine Cerebral Cortex and Corticospinal TractsObjective: To provide neuroelectrophysiological information for the research of spinal cord injury rehabilitation of canine. To record and analyze the physiological signals of canine cerebral cortex and CSTs.Methods: The single microelectrode was plugged into the cerebral cortex and spinal cord of canine. The neuro-electrical signals were recorded from motor cortex and CSTs with Cerebus System. The characteristics of the recorded signals including wave length, amplitude, and discharge frequency etc, were analyzed with Off-line Sorter and Neuroexplorer softwares.Results: 1. Continuously and steadily spontaneous electrophysiological signals were recorded from the motor cortex and spinal cord of canine. 2. The waveform of the signals was independent bidirectional and the wave amplitudes were at a grade of hundred microvoltage. 3. The spontaneous electrophysiological signals were paroxysmal in motor cortex and spinal cord of canine as revealed by Neuroexplorer.Conclusions: 1. Platinum-glass microelectrode can be used to record the neuroelectrophysiological signals from the motor cortex and spinal cord of canine. 2. The characteristics of the recorded signals and the regions single microelectrode plugged into in spinal cord of canine indicate that CST detected with the electro-signals in spinal cord originates from motor cortex.