Spatial distribution of synaptic vesicles in presynaptic terminals: Computer simulation

A procedure for computer simulation is proposed, which allows one to quantitatively characterize the spatial distribution of synaptic vesicles in presynaptic terminals (PST) using ultrathin sections of such terminals. The procedure includes three stages: simulation, topographical analysis, and comparison. At the first stage, the spatial distribution of vesicles within a PST and the process of random sectioning of it are simulated using the corresponding mathematical model. At the second stage, the topographical distribution of vesicle profiles within the plane of PST section is estimated; three respective approaches have been used: (i) nearest neighbor distance distribution; (ii) minimal spanning tree; and (iii) Voronoi paving. At the third stage, the simulated parameters are compared with the parameters of native terminal sections; when the coincidence of these two parameter groups is satisfactory, we believe that the simulated spatial distribution agrees with the real distribution. The software for the procedure is written in C++ programing langage. The results of a pilot study on ultrathin sections of cultured rat hippocampal neurons showed that the method offers broad possibilities for spatial interpretation and quantitative characterization of distributions of synaptic vesicles.