Neuronal brain injury after cerebral ischemic stroke is ameliorated after subsequent administration of (R)-ketamine, but not (S)-ketamine.

Although stroke is the most common acute cerebrovascular disease, there are no currently effective therapeutic drugs for ischemic stroke. (R,S)-ketamine has been shown to protect against brain injury in rodents after middle cerebral artery occlusion (MCAO). Interestingly, we reported that (R)-ketamine has greater beneficial effects than (S)-ketamine in animal models of depression and Parkinson's disease. This study was undertaken whether two enantiomers of ketamine show neuroprotective effects in MCAO model. MCAO-induced brain injury and behavioral abnormalities in mice was attenuated by subsequent administration of (R)-ketamine (10 mg/kg, twice, 1 and 24 h after MCAO), but not (S)-ketamine (10 mg/kg, twice, 1 and 24 h after MCAO). Furthermore, the treatment with (R)-ketamine (10 mg/kg, twice, 30 min before and 24 h after MCAO) significantly protected against brain injury and behavioral abnormalities in mice after MCAO. These findings suggest that (R)-ketamine can protect against neuronal injury and behavioral abnormalities in mice after MCAO. Therefore, it is likely that (R)-ketamine could represent a therapeutic drug for ischemic stroke.