Figure 5.
Simulated effects of a neighboring synapse on the 2pEPSC kinetics and the parameters estimated by NSFA. A, Synapse S1 is stimulated by uncaging (see Materials and Methods) in the presence of another neighboring synapse S2 located at a distance of r from S1. Both S1 and S2 have 100 channels with a single-channel conductance (γ) of 10 pS. To remove an effect of noise, a Gaussian noise was not added in this simulation. B, Averaged traces of simulated 2pEPSCs in the absence (gray) and presence (black) of the neighboring synapse at various distances. Responses at S1 and S2 were summated linearly. C, Relative amplitude and kinetics of 2pEPSCs induced in the presence of the neighboring synapse at r μm from S1. The rise represents a 10-90% rise time, and the decay represents a 62% decay time of simulated 2pEPSCs. The parameters are normalized to values in the absence of S2 (horizontal dotted lines). The vertical dotted lines in C and D separate regions with different effects of S2 on the kinetics and estimated parameters. D, Estimated parameters by NSFA: γ, single-channel conductance; Po, peak, peak open probability; N, number of functional AMPA receptors. The decay phases 40 ms from the apparent peak of 100 traces of summated 2pEPSCs were analyzed. The estimated parameters are normalized to values in the absence of a neighboring synapse. Data were represented by mean ± SEM (n = 3). These simulations indicate that the kinetics and NSFA parameters are barely affected by neighboring synapses when they are further than 2.5 μm.