Effect of tetramethylpyrazine on function of spatial learning and memory in rat after focal cerebral ischemia

Objective: To investigate the effects of tetramethylpyrazine on function of spatial learning and memory in rat after focal cerebral ischemia. Methods: The focal cerebral ischemic model was established by introducing an intraluminal filament into the left middle cerebral artery of the rat, then tetramethylpyrazine was administered introperitoneally after the operation and afterward once a day for 2 weeks. The spatial learning and memory function was studied by Morris water maze test. Niss1 staining technique was conducted for observing the morphology of neurons in cortex and hippocampus. Results: The ischemia-control group exhibited seriously spatial learning and memory deficits in both place navigation trail and spatial probe trial. In place navigation trial, the mean values of escape latency of lower-dose, middle-dose and higher-dose tetramethylpyrazine groups were shorter than those of ischemia-control group(P<0.01). In spatial probe trial, there were significant difference in the time percentage of spending in the former platform quadrant and frequency of crossing the former platform site between lower, middle and higher-dose tetramethylpyrazine groups and ischemia-control group(P<0.01). Compared with ischemia-control group, lower, middle and higher-dose tetramethylpyrazine groups had more neurons of niss1 staining in ipsilateral parietal cortex(P<0.01). The cell numbers of total neurons of hippocampus had no significant difference between lower, middle and higher-dose tetramethylpyrazine groups and ischemia-control group. Conclusion: Tetramethylpyrazine improves the rat spatial learning and memory ability after focal cerebral ischemia, and the neuroprotective role of the drug in new cortex may be involved in its mechanism.