Figure 4.

Short-Term Synaptic Dynamics of Excitatory Monosynaptic Connections In Vivo

(A and B) In vivo z stack image (A) and biocytin reconstruction (B) from a triplet of pyramidal neurons. Colors in (B) correspond to cell numbers in (A). Lighter cell shading represents axons.

(C) Example averaged synaptic response from cell 1 to cell 2 shown in (A) and (B). Left: average response triggered by the first AP (AP1) of a doublet evoked by current injection. Red number 1 highlights uEPSP1 evoked by AP1. Dashed lines show points of measurement of the amplitude of uEPSP1. Middle: averaged synaptic response triggered by the second AP (AP2) of the doublet. Blue number 2 indicates uEPSP2 evoked by AP2. Dashed line from uEPSP1 shows part of the overlaid decay phase of the normalized response to a single uEPSP from the same connection averaged with the same inter-spike intervals (see also Experimental Procedures); vertical dashed line shows time point used to measure amplitude of uEPSP2. Right: overlay of uEPSP1 and uEPSP2 centered at their peak response; this example shows paired-pulse facilitation. V_m mark shows −60.8 mV.

(D and E) Same as in (C) but for different example connections showing (D) a PPR of nearly 1 and (E) an example connection with paired-pulse depression. V_m mark in (D) shows −66.0 mV; in (E), it shows −60.0 mV.

(F) Population analysis shows that there is no difference in amplitude of uEPSP1 and uEPSP2. Gray lines show individual examples, and filled circles indicate the mean ± SEM. Red indicates uEPSP1, and blue indicates uEPSP2.

(G) Graph of the PPR with circles showing individual connections; bar shows population mean with SEM.

(H) The PPR plotted as a function of the amplitude of uEPSP1.

(I) The PPR plotted as a function of the CV calculated from the trial-by-trial amplitude of uEPSP1.

See also Figure S4.