Differences in the release site location influence AMPAR activity. (A) Rod 1 along with its postsynaptic partners. HCs 1 and 2 are shown in yellow (HC1) and green (HC2), respectively. Ribbons are in transparent blue. Rod membranes have been removed for easier visualization. Visible release sites are denoted by arrows. Graphs plot time-dependent activation of AMPARs by release at six different sites, three on each face of the ribbon. Responses of the two HCs beneath each rod terminal (HC1 and HC2) are plotted separately. (B) Illustration of rod 2 with graphs of AMPAR activity in HC1 and HC2. Site-to-site variability remained after increasing the ECV from 0.11 to 0.3. (C) Illustration of rod 3 with graphs of AMPAR activity in HC1 and HC2. (D) Illustration of rod 4 with graphs of AMPAR activity in HC1 and HC2. (E) Frequency histogram of the peak percentage of activated HC AMPA (gray) and RBP mGluR6 receptors (black) produced by release at different ribbon sites. For these simulations, we increased the number of AMPARs on each HC from 200 to 500. Graphs plot the mean ± SD of 25 simulations.