Establish Of A New Model For Spinal Cord Injury In Rats And Effects Of Salvianolic Acid B On The Injury

Objective:Establishing new model of spinal cord injury without damage of vertebrate; Based on the model to investigate the effect of Salvianolic acid B, a major components of the traditional Chinese medicine Salvia miltiorrhiza on the intracellular signal protein after spinal cord injury. Method:1. Model establishment of lumbar spinal cord injury: under general anesthesia and asepsis environment, make a longitudinal incision just along the spine. Locate the spinous process of T9 & T10 by position the L3-L4 gap like what normal done clinically, insert the needle, which had been reshaped as a injury instrument, between T9 & T10 at the left of spinal processes into the spinal cavity and spinal cord. Make the needle swing only to left direction and lift up and down several times at the same time. By the above, model of a unilateral(left) lumbar spinal cord dissociative injury was established. The success of the model establishment was evaluated by observation of paralysis of the left hindlimb and the measurement of the grasp power and thermal sensitivity. 2. The effect of local injection of Salvianolic acid B on the expression of Pir B and Erk1/2 were investigated by indirect immunofluoresence and western-blot methods. The male SD rats were used in this study and were divided into three groups, 5~6 SD rat/each group. Group A: normal rats without any treatment including surgery; Group B: unilateral(left) lumbar spinal cord dissociative injury only, with local injection 0.9% saline, 30ml/rat; Group C: unilateral(left) lumbar spinal cord dissociative injury only with local injection Salvianolic acid B solution prepared by saline, 5mg/kg, 30ml in volume. After 24 h, 1week and 2 weeks of spinal cord injury, the grasp power was measured and the spinal cord samples were collected after 2 weeks of injury. The expression of Pir B and Erk1/2 were examined by immunofluorescence and western-blot. Results:The rats after unilateral( left) lumbar spinal cord dissociative injury showed obvious dysfunction in motor function. They couldn’t walk normally while the left hindlimb appeared paralyzed and drag-and-walk. However, there were no complications of gatism and infection, the general situation like drinking and eating looked was in good condition. The grasp power and thermal; sensitivity of left hindlimb were significantly abate/lost( p<0.05). The skin incision site looked swelling at 24 h of surgery, the incision healed around 1 week after surgery and completely recovered after 4 weeks of surgery. When opening the vertebrate at 2 weeks of injury, the injury site was found in the lumbar area. Injury spinal cord appeared obvious swelling with congestion, local soften and liquefaction. Under microscope with HE staining, the injury area lost the normal spinal morphology. The grey and white matter couldn’t be recognized and some longitudinal nerve bundles were breakdown. In those rats with Salvianolic acid B local injection while injury model established, the grasp power for their left hindlimbs after 2 weeks of injury were improved somewhat compared to those with unilateral(left) lumbar spinal cord dissociative injury only(p <0.05). The immunofluorescence for Pir B indicated that there was no obvious Pir B expression in normal rat spinal cord. The immunofluorescent staining was increased in the ipsilateral(injury side) after 2 weeks of left lumbar spinal cord dissociative injury. The expression of Pir B was down-regulated after the treatment of Salvianolic acid B local injection for two weeks(p <0.05). Meanwhile, the expression of Erk1/2 was detected increased after Salvianolic acid B treatment(p <0.05). Conclusion:1. the rat model of unilateral( left) lumbar spinal cord dissociative injury established in this study showed many advantages than some others, for example, very simply in operation, precise in the position of injury, no damage to vertebrate, no need to open the spinal cavity, the less probability for infection, low incidence of complications. The model offered a tool for exploring some new medicines/ therapeutics preclinically. The long term efficacy of some new medicine/ pharmaceutics could be realized based on the longer survival of model animals. The special injury instrument from modified syringe needle offered a privilege the possibility of applying some preparation locally. In one word, the model was successful with many advantages. 2. the intraspinal medication with Salvianolic acid B intraspinal might decrease the Pir B expression and increase Erk1/2 expression. Salvianolic acid B might play some role in improving the recovery of spinal cord injury.