Vigabatrin enhanced heteroexchange GABA release.A, Comparison of the response to 10 mm NPA of a neuron on a dish treated overnight with vigabatrin (100 μm) with that of a control neuron from a sister dish.B, Composite average of the responses to 10 mm NPA for neurons treated with 100 μmvigabatrin overnight (n = 32) as compared with the responses for control neurons (n = 31). Baseline was leak-subtracted in A and B.C, NPA response versus [vigabatrin] at <1 d. The AUC (i.e., total charge transfer) of the response to 10 mm NPA was plotted as the percentage of control. Neurons were treated with different concentrations of vigabatrin for 12–24 hr. D, NPA response versus [vigabatrin] at 3–4 d. Plotted is the AUC (as percentage of control) of the mean responses to 1 mm NPA for neurons that were treated with different concentrations of vigabatrin for 3–4 d. Neurons in D are the same as those in Figure 4B (*p < 0.05; **p < 0.01; ***p < 0.001).