Figure 1.

System X_AG and x_c- glutamate uptake in crude (mixed) synaptosomes from striatum and hippocampus of gp120 and wild-type (WT) mice. The maximal velocity of X_AG (i.e., sodium-dependent) and x_c- (i.e., sodium-independent) glutamate uptake (pmol/mg protein/time) was plotted as a function of the external unlabeled glutamate concentration. Saturation analysis was performed using 100 nM of L-[³H]-glutamate in the absence or presence of unlabeled L-glutamate (0-100 μM) to give the final concentrations shown (x-axis). The maximal velocity (V_max) and the affinity (K_m) constants were determined by nonlinear regression analysis by applying the Michaelis Menten Equation to the data. Significant differences in the estimated V_max and K_m values were determined by analysis of variance (ANOVA). A significant (p<0.05) reduction in the V_max of both systems X_AG and x_c- glutamate uptake was observed in striatum (A) but not hippocampus (B) of gp120 mice compared to WT. There were no significant group differences in the K_m (affinity) for glutamate in either glutamate uptake systems in striatum and hippocampus. Data are expressed as mean ± SEM (n=4/group).