Effect of radix salviae miltiorrhizae on EAA and IAA during cerebral ischemia in gerbils: a microdialysis study

The concentrations of amino acids (AA), stroke index and infarct area were determined in 26 gerbils which were divided into 3 groups: RSM-treated (n = 8), Saline-treated (n = 10) and sham-operated (n = 8). The levels of AA were measured with microdialysis technique in cerebral cortex. The concentrations of neurotransmitter AA, as Glu and GABA and Asp, were significantly increased during the first 60 min after CCA ligation, while the concentrations of non-neurotransmitter AA, as Thr and Ser, had no significant changes. In RSM-treated gerbils, the level of Glu was significantly lower than that of the saline-treated, but the GABA in RSM-treated was significantly higher than that of the saline-treated. The ratio of Glu/GABA was significantly decreased after ischemia. The RSM could improve the reduction of ratio of Glu/GABA during 0-30 min and 91-120 min after cerebral ischemia. There were statistically significant decrease in terms of stroke index in RSM-treated group when compared with saline-treated group at 24 h and 16 h after CCA ligation respectively. The RSM has a tendency to decrease the size of infarct area, but no statistical difference. The results suggest that the neurotransmitter AA involve in the pathophysiological procedures of cerebral ischemia and the RSM can attenuate dysfunctions of EAA and IAA. Furthermore, the results also imply that there may be an alternate way to treat cerebral ischemia by inhibiting the presynaptic releasing of Glu and stimulating the releasing of GABA.