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. 2024 Nov 18;22(11):e3002879. doi: 10.1371/journal.pbio.3002879

Fig 1. Forskolin-induced chemical potentiation is primarily mediated by an increase in RRP size.

Fig 1

(A) Left panel: schematic illustration of the paired recording. Single MFBs were stimulated in the tight-seal, cell-attached configuration, while postsynaptic CA3-PNs were simultaneously recorded in the whole-cell voltage-clamp configuration. Right top panel: 50-Hz train of 10 stimuli. Right bottom panel: overlay of average EPSCs before (“Ctrl,” gray) and in the presence of 50 μM forskolin (“FSK,” red). (B) Normalized EPSC1 peak amplitude plotted against experimental time. Red horizontal line indicates the application of forskolin (“FSK”). Dashed line indicates 100% baseline. Note that the onset of forskolin application is the time point of switching solutions from forskolin-free ACSF to forskolin-containing ACSF. Forskolin-containing ACSF reached the recording chamber about 60–90 s after the onset of forskolin application. Data from 8 pairs (8 rats). (C) Summary bar graph of EPSC1 peak amplitudes before (“Ctrl,” gray) and in the presence of 50 μM forskolin (“FSK,” red). Bars and whiskers show mean + SEM; P = 0.0078, Wilcoxon signed-rank test. (D) Summary bar graph of PPR (EPSC2/EPSC1) before (“Ctrl,” gray) and in the presence of 50 μM forskolin (“FSK,” red). Bars and whiskers show mean + SEM; P = 0.0156, Wilcoxon signed-rank test. (E) Cumulative plot of EPSC peak amplitudes during a 50-Hz train with 10 stimuli before (“Ctrl,” gray) and in the presence of 50 μM forskolin (“FSK,” red). Data points during the last 4 stimuli (at time points ≥120 ms) were fit by linear regression and back-extrapolated to time point 0. (F–H) Summary bar graphs of RRP (F; P = 0.0078), Pr (G; P = 0.0391), and refilling rate (H; P = 0.7422, Wilcoxon signed-rank tests), estimated from the cumulative EPSC plot (E), before (“Ctrl,” gray) and in the presence of 50 μM forskolin (“FSK,” red). Bars and whiskers show mean + SEM. See S1 and S2 Figs. Numerical values for this figure are detailed at https://doi.org/10.15479/AT:ISTA:18296. ACSF, artificial cerebrospinal fluid; EPSC, excitatory postsynaptic current; MFB, mossy fiber bouton; PN, pyramidal neuron; PPR, paired-pulse ratio; RRP, readily releasable pool; SEM, standard error of the mean.