Fig. 2. Increased AMPA receptor unitary conductance (γ) during sLTP, but not cLTP.
a A representative LTP experiment with sample traces for baseline and post TBS – the mean of selected records for analysis, superimposed with peak-scaled individual traces (10 successive sweeps, thin lines; baseline = grey, LTP = black). Scaled trace is from the baseline normalized to the LTP. Scale bars: 20 pA and 10 ms. Two inputs were stimulated alternately and cTBS (3 x TBS with an inter-episode interval of 10 s; blue arrows) delivered to one input (filled symbols) with the second input (open symbols) serving as a control (Con). b Levels of cTBS-induced LTP (cLTP) for control and test inputs, quantified during the 10 min epoch after the induction (mean ± SEM, n = 22 neurons from 15 animals; t21 = 8.545, p < 0.0001, two-sided paired Student’s t test). c Corresponding current–variance relationship of the EPSCs for the test input. The unitary channel conductance (γ) of AMPA receptors was estimated during baseline (grey) and after the induction of LTP (LTP10’; black). d Grouped comparison of control and test input γ estimates for baseline and the initial 10 min epoch (LTP10’) and the subsequent 10 min epoch (LTP20’). n = 22 neurons from 15 animals. e, f Summary plot for the γ at baseline (left) and LTP10’ (right) for control (e) and test (f) inputs. Individual values from each neuron are connected by lines. Circles indicate mean values. g Cumulative distribution of the same data set for LTP10’. Dotted lines indicate the mean values for each input. h, i Analysis of the relationships of γ with LTP (p = 0.6517, F(1,20) = 0.2101, F-test) (h) and EPSC decay time (p = 0.9521, F(1,20) = 0.0037, F-test) (i). Linear regression with 95% confidence intervals (shaded) for the amount of cLTP and the corresponding level of γ. j–r Equivalent analysis for the LTP induced by sTBS (3 x TBS at inter-episode interval of 10 min; see arrows). The whole-cell recordings were obtained after the second TBS. This was necessary due to the lability of LTP washout. k Levels of sTBS-induced LTP (sLTP) for control and test inputs, quantified during the 10 min epoch after the induction (n = 23 neurons from 17 animals; t22 = 5.238, p < 0.0001, two-sided paired Student’s t test). m–o Statistical analysis between control and test pathways (t22 = 3.220, p = 0.0039 for baseline and t22 = 6.123, p < 0.0001 for LTP10’, two-sided paired Student’s t test) (m) and within pathway analysis for control (t22 = 1.065, p = 0.2986, two-sided paired Student’s t test) (n) and test (t22 = 3.753, p = 0.0011, two-sided paired Student’s t test) (o) pathway reveals a time- and pathway-dependent increase in γ. Note that higher conductance was observed in the test input (o) compared to the control (n) under the “baseline” state, suggesting that the first + second TBS were sufficient to increase γ. The third TBS triggered a small but discernible further increase in γ. q, r Analysis of the relationships of γ with LTP (p = 0.0225, F(1, 21) = 6.066, F-test) (q) and decay time of EPSCs (p = 0.0712, F(1,21) = 3.612, F-test) (r). Data are presented as mean ± SEM. Source data are provided as a Source Data file.