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BACKGROUND: Recent studies have shown that the selective inhibitor of c-Jun N-terminal kinases (JNKs) signaling pathway, SP600125, exhibits neuronal protective effects in a rat model of brain ischemia/reperfusion.OBJECTIVE: To determine the mechanisms of neuroprotective effects of SP600125 in a rat model of brain ischemia/reperfusion, and determine the role of the JNK signaling pathway in SP600125-induced effects.DESIGN, TIME AND SETTING: A randomized, controlled, animal experiment was performed at the Animal Experiment Center, Medical School of Xi'an Jiaotong University from June 2007 to September 2008.MATERIALS: SP600125 was provided by Biosource, USA; rabbit anti-phospho-JNK (Thr183/Tyr185) polyclonal antibody from Cell Signaling Technology, USA; rabbit anti-X-ray repair cross-complementing protein 1 (XRCC1) and anti-Ku70 polyclonal antibodies from Santa Cruz Biotechnology, USA; and TUNEL kit from Beijing Huamei Biology, China.METHODS: A total of 108 male, 4-month-old, Sprague Dawley rats were randomly assigned to three groups, with 36 rats per group. The sham operation group and ischemia/reperfusion group (I/R group) were intracerebroventricularly injected with 10 μL 1% DMSO. The SP600125-treated group (pre-SP group) was given 10 μL SP600125 (3 μg/μL). Thirty minutes later, brain ischemia was induced in the I/R and pre-SP groups using the four-vessel occlusion method. Specifically, whole brain ischemia was induced for 6 minutes, and the clips were released to restore carotid artery blood flow. Rats from each group were observed at 2, 6, 12, 24, 48, and 72 hours, with 6 rats for each time point. The sham operation group was treated with the same surgical exposure procedures, with exception of occlusion of the carotid artery.MAIN OUTCOME MEASURES: Hematoxylin-eosin staining was used to observe neuronal survival in the hippocampal CA1 region, TUNEL was used to detect apoptosis in the hippocampal CA1 region, and immunohistochemistry was used to detect expression of phospho-JNK, XRCC1, and Ku70.RESULTS: Following brain ischemia/reperfusion, neuronal survival significantly decreased, and the number of apoptotic cells significantly increased (P