Abstract: BACKGROUND: Hemorheological changes following spinal cord injury can cause microcirculation disorder, induce tissue ischemia and hypoxia, and aggravate the secondary injury to spinal cord tissue.
OBJECTIVE: To observe the changes in hemorheological indexes at different time points after tetramethylpyrazine intervention in rats with complete spinal cord transection.
METHODS: Fifty-four 8-week-old female Sprague-Dawley rats were randomly divided into three groups (n=18 per group): sham operation group, model group, and tetramethylpyrazine group. Only laminectomy was performed in the sham operation group, while the T10 segment was completely transected with a 2 mm defect gap in the model and tetramethylpyrazine groups by a self-made double-edge microshear. After model preparation, tetramethylpyrazine group was given intraperitoneal injection of tetramethylpyrazine hydrochloride, 200 mg/kg per day, for 5 consecutive days. Abdominal aorta blood samples were taken 7, 14, and 28 days after operation for measuring whole blood viscosity (low, high and medium shear rates), plasma viscosity, hematocrit, erythrocyte aggregation index, erythrocyte deformability index, erythrocyte rigidity index, and erythrocyte electrophoresis index.
RESULTS AND CONCLUSION: The whole blood viscosity (low, high, and medium shear rates) and plasma viscosity in the model group were significantly higher than those in the sham group at 7, 14, and 28 days after spinal cord injury (P < 0.05). Hematocrit was significantly higher but erythrocyte rigidity index and erythrocyte electrophoresis index were significantly lower in the model group than the sham group at 14 days after spinal cord injury (P < 0.05). Tetramethylpyrazine significantly reduced whole blood viscosity (low, high, and medium shear rates) and plasma viscosity at 7 days after spinal cord injury (P < 0.05). Tetramethylpyrazine significantly increased erythrocyte deformability index (P < 0.05) and certainly but not significantly improved blood viscosity at 14 days after spinal cord injury (P > 0.05). Tetramethylpyrazine significantly improved whole blood viscosity (hyposhear) and plasma viscosity at 28 days after spinal cord injury (P < 0.05). To conclude, after spinal cord injury, the whole blood viscosity and plasma viscosity can increase and erythrocyte indexes can also change to varying degrees. The use of tetramethylpyrazine can improve the deterioration of early hemorheological indexes and improve microcirculation disorders.

Key words: tetramethylpyrazine, spinal cord injury, hemorheology, microcirculation disorder, angiogenesis, endothelial cell