BACKGROUND: Focal cerebral ischemia model in rats should be established under drugged state by surgery operation, but anaesthetic drug may influence the outcome of focal cerebral ischemia.OBJECTIVE: To observe the effects of ketamine anesthesia on the pathological outcome of focal cerebral ischemia model in rats, and perform control with pentobarbital.DESIGN: Randomized controlled animal experiment.SETTING: Center of Experimental Animal and Department of Pathology of Second Affiliated Hospital, School of Medicine, Xi'an Jiaotong University.MATERIALS: The experiment was performed in the Center of Experimental Animal and Department of Pathology of Second Affiliated Hospital,School of Medicine, Xi'an Jiaotong University from May 2004 to March 2005. Thirty male SD rats were randomly assigned into pentobarbital group and ketamine group with 15 rats in each group.METHODS: The rats in the pentobarbital group and ketamine group were subjected to 40 mg/kg pentobarbital and 60 mg/kg ketamine by abdominal anaesthesia, respectively. The permanent middle cerebral artery occlusion (MCAO) was performed in rats by thread embolism in cavity in order to induce cerebral ischemia after abolition of righting reflex.MAIN OUTCOME MEASURES: ①A modified Bederson's scoring system was adopted to determine the neurological functional deficit at hour 4 after the MCAO. ②Five rats from each group were selected at hour 24 after MCAO. They were killed and their brain was stained with 20 g/L 2,-3,-5-triphenyltetrazolium hydrochloride (TTC). The infarct volume was determined. ③ MCAO was performed for 72 hours and mortality rate of two groups were recorded. Four rats in each group were re-anesthetized. They were killed and their brain was gained. Survival neurons were detected with toluidine blue staining.RESULTS: Totally 30 rats were involved in the result analysis. ①There was no significant difference in neurological score 4 hours after MCAO between pentobarbital group and ketamine group (1.46±0.98,1.38±0.68 ,P＞0.05). ②The infarct volume in the ketamine group was less than that in the pentobarbital group at hour 24 after MCAO [(28.1±4.11)%,37.8±4.95]%, P＜0.05]. ③The mortality rate 72 hours after ischemia was not significantly different between pentobarbital group and ketamine group (42% vs 33%,P＞0.05). But neuron density in penumbra in the ketamine group was higher than that in the pentobarbital group [(836±15),(740±24) numbers/mm2, P＜0.05].CONCLUSION: ①The ketamine anesthesia induces minor brain injury in setting of the focal cerebral ischemia model in rats. ②When neuroprotective effects of procedures or drugs being studied are evaluated in this focal cerebral ischemia model, they might provide no additional advantage to cerebral ischemia.