Previous reports have indicated that isosteviol sodium (STVNa) has neuroprotective effects against acute focal cerebral ischemia in rats; however, the exact underlying mechanisms and ideal treatment paradigm are not known. To find a reasonable method for STVNa administration and to determine its possible therapeutic mechanisms, we characterized the protective effects of single-dose and multiple-dose STVNa in cerebral ischemic/reperfusion (I/R) injury in rats. Single and multiple treatments with 10 mg/kg STVNa were administered intraperitoneally after injury to investigate its neuroprotective effects. Neurobehavioral deficits and infarct volume were assessed 7 d after ischemia. Both STVNa treatments reduced infarct volumes, improved neurological behaviors, preserved cellular morphology, enhanced neuronal survival, and suppressed cell apoptosis. Multiple treatments performed better than single treatment. Reactive astrogliosis was apparent at 7 d after injury and was significantly inhibited by multiple STVNa treatments but not single treatment. These results indicate that STVNa exerts neuroprotection by different mechanisms in the acute and delayed phases of I/R. Specifically, STVNa neuroprotection in the delayed phase of injury was found to be accompanied with the inhibition of astrogliosis.
Keywords: astrogliosis; cerebral ischemic/reperfusion injury; isosteviol sodium; rat.