Inhibition of excitatory amino acid efflux contributes to protective effects of puerarin against cerebral ischemia in rats.

OBJECTIVE To investigate whether the protective effects of puerarine (Pur) against cerebral ischemia is associated with depressing the extracellular levels of amino acid transmitters in brain of rats. METHODS Male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) for 60 min followed by 24 h reperfusion. Pur (50, 100 mg/kg, i.p.) was administered at the onset of MCAO. The infarct rate and edema rate were detected on TTC (2,3,5-triphenyltetrazolium chloride)-stained coronal sections. The extracellular levels of amino acid transmitters were monitored in striatum of rats with ischemic/reperfusion injury using in vivo microdialysis technique. Furthermore, the protective effects of Pur against glutamate-induced neurotoxicity were detected. Glutamate-induced apoptotic and necrotic cells in hippocampus were estimated by flow cytometric analysis of Annexin-V and PI labeling cells. RESULTS Pur (100 mg/kg) significantly decreased infarct size by 31.6% (P<0.05), reduced edema volume (P<0.05), and improved neurological functions (P<0.05) following MCAO. In these rats, the ischemia-induced extracellular levels of aspartate (Asp), glutamate (Glu), y-aminobutyric acid (GABA), and taurine (Tau) were significantly reduced in striatum of vehicle-treated animals by 54.7%, 56.7%, 75.8%, and 68.1% (P<0.01 and P<0.05). Pur reduced the peak values of Glu and Asp more obviously than those of GABA and Tau, and the rate of Glu/GABA during MCAO markedly decreased in Pur-treated MCAO rats, compared with the vehicle-treated MCAO rats. Meanwhile, apoptosis and necrosis induced by Glu in cultured hippocampal neurons were significantly reduced after Pur treatment. CONCLUSION Acute treatment with Pur at the onset of occlusion significantly depresses ischemia-induced efflux of amino acids, especially, excitotoxicity in the striatum, a mechanism underlying the neuroprotective effect on cellular survival.