Fig. 3: Electrophysiological characterization of functional properties in autaptic glutamatergic neurons overexpressing haSyn.

A Representative whole-cell patch clamp recordings traces of evoked EPSC amplitudes stimulated at 0.2 Hz from neurons infected with eGFP (A1) or haSyn lentivirus (A2). B Quantification of eEPSC amplitudes in neurons expressing eGFP alone (n = 69) or haSyn (n = 70). C Quantifications of miniature EPSC amplitudes (C) and frequency (D) recorded in the presence of 300 nM TTX for neurons expressing eGFP (n = 53) or haSyn (n = 52). E–J Normalised eEPSC amplitudes from whole-cell patch clamp recordings of neurons stimulated with trains of either 50 APs at 10 Hz (E) or 100 APs at 40 Hz (H) stimulation. Note that the presynaptic plasticity from neurons expressing eGFP or haSyn appeared highly similar, resulting in depression of the eEPSC before reaching a depressed steady state. F, I Quantification of the paired pulse ratio (PPR) as the ratio of the first two eEPSCs of each stimulation condition. No differences in PPR were observed between neurons expressing eGFP or haSyn when stimulated at 10 Hz (F) or 40 Hz (I). G, J Quantification of the steady-state depression during the stimulation trains, as the average normalised amplitude over the last 10 eEPSCs. For 10 Hz (G), n = 61 for eGFP, n = 67 for haSyn. For 40 Hz (J), n = 59 for eGFP, n = 65 for haSyn. K–N Estimation of readily-releasable pool (RRP) size in autaptic glutamatergic neurons overexpressing haSyn. K Sample traces showing the current elicited by the application of 500 mM sucrose, representing fusion of SVs in the RRP in neurons expressing eGFP (K1) or haSyn (K2). L Quantification of RRP size using the sucrose application method in neurons expressing eGFP or haSyn. M Quantification of the RRP estimation based on extrapolating from cumulative eEPSCs evoked by stimulating neurons at 40 Hz. N Release probability from neurons expressing eGFP or haSyn. n = 45 for eGFP, n = 48 for haSyn. Data collected from 12 independent cultures with three different lentivirus batches. Data are expressed as mean ± SEM; Student’s t-test or Mann-Whitney test, for normally and not-normally distributed data, respectively.