Fig. 3

Enhancement of the activity-dependent increment of SpH fluorescence (ΔSpH) by β-phorbol esters (BPE). a The fEPSP was monitored at 0.033 Hz using a two-pulse protocol (insets left, before and right, after PDAc); the peak amplitude of the first fEPSP (filled circles, mean ± SEM, n = 8 slices) and the fiber volley amplitude (open diamonds, mean ± SEM, n = 3 slices). Each data was normalized to the mean of five values preceding the sampling 1. The numbered red double lines indicate image sampling 1 and 2 when repetitive stimulations were applied at 10 Hz for 10 s. Drugs were bath-applied for the indicated periods. b The difference images of the same region before (left, sampling 1) and after PDAc (10 μM) (right, sampling 2). c The sample ΔSpH traces during MF stimulation of three LMFBs in b (indicated by white arrows) are compared before (sampling 1, black) and after PDAc (sampling 2, blue). d In some LMFBs, the negligibly small ΔSpH before (sampling 1, black) became obvious after PDAc (sampling 2, blue). e Each LMFB was plotted two-dimensionally to the sampling-1 (control) and the sampling-2 (test) values of ΔSpH; vehicle alone (open circles, n = 31 boutons, 5 slices), 4α-phorbol (yellow squares, n = 30 boutons, 6 slices) and PDAc (blue diamonds, n = 65 boutons, 10 slices). The magenta line shows that both are equal. f Cumulative probability plots of the ratio value of the ΔSpH at sampling 2 divided by that at sampling 1 (ratio-2/1 of ΔSpH); vehicle alone (black line), 4α-phorbol (gray line) and PDAc (blue line)