Abstract: AIM: To study theProtective effect and mechanism of melatonin onlearning and memory in mice with repeated cerebral ischemia and reperfusion and its mechanism.METHODS: The models of repeated cere-bral ischemia-reperfusion were established in mice.The function oflearning and memory was tested by the electric mare method,and the concentrations of MDA and NO were measured by colorimetric method and nitric-reduction method in brain tissue.RESULTS: MT could obviously improve the function oflearning and memory of model mice,inhibit cerebral dropsy,andlower the content of MDA and NO in cerebral tissue.CONCLUSION: MT shows significantlyProtective effect against repeated isch-emia-reperfusion injury in mice,and the mechanism might be related to inhibit the rise of MDA and NO in brain tissue.

Key words: pharmacology, melotonin, cerebral ischemia-reperfusion, malonydialdehyde, nitrogen monox-ide