Axonal synaptic events are filtered by the axon. (A) Schematic reconstruction of an MLI that was successfully stimulated in several axonal varicosities (arrowheads; somatodendritic domain is in magenta, and axon is in green). (B) Representative traces of individual ASCs evoked in the positions indicated in A. The vertical dotted line indicates timing of the laser pulse. (C) Amplitude distribution of all the recorded ASCs (gray; n = 64 sites from 33 cells) and from four selected individual sites to illustrate the degree of intra-site variability (colored histograms and associated Gaussian fits, n = 3–12 events/site). (D) Plot of ASC amplitude as a function of the distance between the soma and the release site. Each circle represents an individual experiment; continuous black line is the exponential fit. The distance at which the amplitudes are reduced to 37% of their extrapolated maximal amplitude (D₃₇) is 56 ± 9 µm (n = 64 sites). Gray lines are the fits of simulated datasets using different autoR synaptic conductance values. The simulation performed with a 3-nS autoR synaptic conductance best fitted experimental data (Chi² values corresponding to the simulations with 1-, 2-, 3-, 4-, and 5-nS autoR conductance: 467.7, 174.3, 166.7, 259.6, and 395.0, respectively). (E) Plot of ASC amplitude as a function of τ_rise. Continuous line is the linear fit (P < 0.01; Pearson’s coefficient: −0.56; n = 23 sites). (F) Plot of ASC τ_decay as a function of τ_rise. Continuous line is the linear fit (P > 0.05; Pearson’s coefficient: 0.02; n = 23 sites).