Fig. 4: Multivesicular release increases the gain and the signal to noise ratio of synapses.
From: Vesicular release probability sets the strength of individual Schaffer collateral synapses
a EPSCs were measured by dual patch-clamp recordings from connected CA3-CA1 pyramidal cell pairs. Perfusion was switched from 1 mM to 4 mM [Ca2+]e, leading to increased EPSC amplitudes. Traces show EPSCs (average of ~40 trials) from the CA1 pyramidal cell. b Traces show the evoked change in fluorescence (average of ~60 trials) from a single bouton in CA1 stratum radiatum. The switching sequence (low - high [Ca2+]e / high - low [Ca2+]e) was reversed between experiments. c Increasing [Ca2+]e from 1 to 4 mM increased the median amplitude of AMPAR-mediated EPSCs by a factor of 6.02, interquartile range (IQR): 3.4–7.5-fold, n = 7 pairs, the median iGluSnFR response by 9.63-fold, IQR: 5.3 –15.2-fold, n = 25 boutons. There is no significant difference between the fold change in AMPARs and iGluSnFR responses (two-sided Mann–Whitney, p = 0.08). d Representative EPSCs (average of ~40 trials) in response to the presynaptic paired-pulse stimulation (ISI 48 ms) recorded in 1 mM and 4 mM [Ca2+]e. e Representative iGluSnFR signals (average of ~60 trials) from a bouton in CA1 in response to the paired-pulse stimulation. f EPSCs showed paired-pulse facilitation in 1 mM [Ca2+]e, (median PPR: 156%, IQR: 140%–189%, n = 7 pairs) and paired-pulse depression in 4 mM [Ca2+]e (median PPR: 86%, IQR: 74%–107%, n = 7 pairs). iGluSnFR responses showed paired-pulse facilitation in 1 mM [Ca2+]e (median PPR: 110%, IQR: 77%–152%, n = 25 boutons) and paired-pulse depression in 4 mM [Ca2+]e (median PPR: 79%, IQR: 74%–95%, n = 25 boutons). There is a significant difference between the AMPARs PPR and the iGluSnFR PPR in 1 mM [Ca2+]e (two-sided Mann–Whitney test, p = 0.03). However, there is no significant difference between the AMPARs PPR and the iGluSnFR PPR in 4 mM [Ca2+]e (two-sided Mann–Whitney test, p = 0.37). Value with a PPR = 0 is not plotted for display purpose but was used for statistics. Values are plotted as median with IQR. Source data are provided as a Source Data file.
