186 CATALYZING INQUIRY
FIGURE 5.18 Summary of synaptic transmission simulations.
(A) Location of selected transmitter release sites and their associated simulated mEPSC traces, each decomposed
into their α3 and α7 nAChR components. Each trace is the average of 100 simulations using MCell. Site 1 is located
at a PSD on nonspine membrane. This site is expected to have a large α3 response and a very small α7 response. At
the other extreme of behavior, sites 3 and 5 are placed over non-PSD spine membrane. Rich in α7 receptors and
poor in α3 receptors, these sites are expected to have large α7 responses and minimal α3 responses. The other sites
are placed at locations expected to give rise to mEPSCs of mixed nAChR origin.
(B) mEPSC amplitudes (decomposed into their α3 and α7 nAChR components) at each of 550 distinct vesicular
release sites. The mEPSC amplitudes are indicated by the diameter of the yellow spherical glyph and demonstrate
a strong dependence on location and underlying geometry.
SOURCE: Courtesy of Tom Bartol, Salk Institute, San Diego, CA.