Abstract: AIM: To investigate the protective effects and the mechanism of low dose aspirin on focal cerebral ischemia-reperfusion rats.Methods: Right middle cerebral artery was occluded by inserting a thread through internal carotid artery for 2 h, and then reperfused for 24 h.6 mg·kg^-1 dose of aspirin was intragastric administered at reperfusion 0 and 6 h.The brain injuried area, the neuronal density, the numbers of apoptotic cells and the ratio of Bcl-2 protein and Bax protein from occluded brain were estimated.The ratio of prostacyclin (PGI₂) and thromboxane (TXA₂) in plasma, the contents of malondialdehyde (MDA), adenosion 5'-triphosphate (ATP) and myeloperoxidase(MPO) in brain tissue from the occluded side were assayed.Apoptosis was measured in paraffin sections with TUNEL method.Bcl-2 and Bax were detected by immunohistochemical staining method.Adjacent sections were stained with hematoxylin and eosin, and neuronal density subfield was counted.The contents of PGI₂ and TXA₂ in plasma were measured by ¹²⁵I radioimmunoassay method.The content of MDA and MPO in brain tissue was determined by biochemical method.The content of ATP in brain tissue was separated by capillary electrophoresis.Results: The injuried area of brain occluded side was dramatically reduced after 6 mg·kg^-1 dose of aspirin was intragastric administrated.Most of neurons in the injuried regions survived ischemia-reperfusion result when 6 mg·kg^-1 dose of aspirin was given, where as most of vehicle group neurons were lost without aspirin treatment.The numbers of apoptotic cells were dramatically reduced by 6 mg·kg^-1 dose of aspirin.The ratio of Bcl-2 and Bax was increased by aspirin.The ratio of PGI₂/TXA₂ in plasma was increased by aspirin.In brain tissue of occluded side, no significant change between 6 mg·kg^-1 and vehicle groups in MDA content, ATP level, and MPO content were discovered.Conclusion: The neuroprotective effects of low dose of aspirin on focal cerebral ischemia-reperfusion rats might be attributed to its effects by increasing the ratio of PGI₂/TXA₂, inhibiting apoptosis and improving the ratio of Bcl-2 Bax.

Key words: aspirin, low dose, focal cerebral ischemia-reperfusion, prostacyclin thromboxane, apoptosis, Bcl-2 Bax