Fig. 2.

Summary of HFS- and photolysis-induced MF long-lasting potentiation. A: HFS-induced MF LTP in 20 neurons, 9 of which were filled with nitrophenyl-EGTA (NPE) or dimethoxy-nitrophenyl-EGTA-4 (DM-NPE-4). Data showed no significant difference in EPSC slope or PPF (data not shown) and were therefore grouped together for analysis. B: average responses of 5 experiments in which photolysis induced long-lasting MF potentiation (●). Average responses in 7 cells containing no caged Ca²⁺ show that light alone has no effect on transmission (○). C: cumulative probability plots summarize results: each point represents the average magnitude of change relative to baseline for a single experiment measured 20–25 min after HFS (○) or photolysis (●). *HFS experiments on cells containing no caged Ca²⁺. D: HFS- and photolysis-induced MF potentiation differ in PPF. Facilitation was persistently reduced in LTP after HFS, but not after photolysis-induced potentiation. Each bar represents a 5-min average of the 2nd EPSC slope divided by average of the 1st. *Significant differences (P < 0.05) compared with 10 min before stimulation. E: cumulative probability graphs of PPF induced by HFS (○) and photolysis (●) and measured 20–25 min after stimulation. *Experiments showing significant changes in PPF.