A, summary of experiments showing that treatment of slices with the GABA transport inhibitor SKF89976A (50 μm) permitted persistent LFS-DEP of four trains of 100 Hz LTP (n = 6; •) but had no effect on the induction of LTP (n = 6; ○). B, summary of experiments showing that a 5 min application of DCG-IV (3 μm) at 10 min after four trains of 100 Hz HFS failed to elicit a persistent depotentiation in control slices (n = 6; ○). In contrast, treatment of slices with SKF89976A (50 μm) permitted persistent DCG-IV-DEP of four trains of 100 Hz LTP (n = 6; •). C, summary of experiments showing that treatment of slices with another GABA transport inhibitor, nipecotic acid (500 μm), permitted persistent LFS-DEP of four trains of 100 Hz LTP (n = 6; •). Field EPSPs in slices that received HFS without LFS exhibited persistent potentiation (n = 6; ○). D, summary of experiments showing that treatment of slices with nipecotic acid (500 μm) also permitted persistent DCG-IV-DEP of four trains of 100 Hz LTP (n = 6).