| Injured axons have limited capacity to regenerate after spinal cord injury in adult mammals. However, they can show remarkable spontaneous functional recovery of locomotion following incomplete spinal cord injury, and the recovery is greatly related to the amounts of spared fibers. Although the correlation between the functional recovery and the amounts of spared fibers has been well studied, very little has been achieved for such correlation after incomplete spinal cord transection.To establish an ideal animal SCI model is the fundmentalpremise to study spinal cord injury and regeneration. The model of spinal cord complete transection is commonly used in the study of spinal cord regeneration recent years, but there still exist some problems. The first is how to confirm the completeness of spinal cord transection. Despite different transecting methods which have been used in many laboratories, no one ideal method, which is easy, reliable and less damageable, could be accepted. Secondly, following moderate or severe spinal cord contusion, 50-70% rats would die within 30 days and there was even a higher mortality after spinal cord complete transection. Therefore, taking steps to raise survival rate became a key point to put the experiment into practice successfully.In the first part of this study, at the level of the T9 segment, the spinal cord was transected conventionally with a sharp blade made from a razor in 12 male SD adult rats. Following operation, 42 % animals showed different degrees of locomotor recovery in all 3 joints of the hindlimbs, from extensive movements (BBB scores: 7) to almost normal stepping with only a few of defects (BBB scores of 19). Sagittal sections of the spinal cord lesion site in the rats with locomotor recovery showed different quantities of neurofilement-imunoreactive residual fibers that were located in the ventral or ventrolateral part of the spinal cord. With the help of a computer, cross sections of lesioned spinal cords were reconstructed in these fibers-spared animals and the percentages of the spared fibers were obtained. Correlational analysis of locomotor recovery as measured by BBB scores and the percentage of spared fibers suggested a notable positeve linear relationship between them (^=0.973), and lessthan 4% spared fibers could result in the movements of all hindlimb joints.During the past two years, we tested different methods, trying to find an easy method of complete spinal cord transection with minor damage to the spinal cord. In the second part of the study, 4 spinal cord transecting methods were used in 32 adult rats. The completeness of transection and the degree of damage were compared. The results approved that a method founded in this study was an ideal one, by which the spinal cord was severed completely and the least degree of damage was caused. The procedure is described as fellows: a laminectomy was performed to expose the T9 segment of the spinal cord. The dura was openned and removed over a length of 2 mm rostracaudally. From the left side to the midline, the dorsal part of the piamater and cord was severed swiftly with a blade made from a razor. Then the right dorsal, the left and right ventral parts were severed in the same plane. Both stumps of the spinal cord were liftedfinally to ensure a complete transection.We improved and modified a whole set of post-operative treatments to raise the survival rate of the animals following complete spinal cord transection, aiming mainly at the problems such as uroschesis, infection, and pressing wound in the body or limb. The mortality dropped from 75% to less than 23% after the treatments.
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