Background:Water dropwort (Oenanthejavanica) as a popular traditional medicine in Asia shows various biological properties including antioxidant activity.In this study,we firstly examined the neuroprotective effect of Oenanthejavanica extract (OJE) in the hippocampal cus ammonis 1 region (CA1 region) of the gerbil subjected to transient cerebral ischemia.Methods:Gerbils were established by the occlusion of common carotid arteries for 5 min.The neuroprotective effect of OJE was estimated by cresyl violet staining.In addition,4 antioxidants (copper,zinc superoxide dismutase [SOD],manganese SOD,catalase,and glutathione peroxidase) immunoreactivities were investigated by immunohistochemistry.Results:Pyramidal neurons in the CA1 region showed neuronal death at 5 days postischemia;at this point in time,all antioxidants immunoreactivities disappeared in CA1 pyramidal neurons and showed in many nonpyramidal cells.Treatment with 200 mg/kg,not 100 mg/kg,OJE protected CA1 pyramidal neurons from ischemic damage.In addition,200 mg/kg OJE treatment increased or maintained antioxidants immunoreactivities.Especially,among the antioxidants,glutathione peroxidase immunoreactivity was effectively increased in the CA1 pyramidal neurons of the OJE-treated sham-operated and ischemia-operated groups.Conclusion:Our present results indicate that treatment with OJE can protect neurons from transient ischemic damage and that the neuroprotective effect may be closely associated with increased or maintained intracellular antioxidant enzymes by OJE.