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. Author manuscript; available in PMC: 2016 Jan 1.
Published in final edited form as: Mov Disord. 2014 Dec 1;30(1):45–53. doi: 10.1002/mds.26103

Figure 2.

Figure 2

Random walk simulations of DA overflow from a quantal release event under normal (5 μM/sec) and PD-like (1 μM/sec) levels of DAT activity. The traces represent diffusional profiles of DA concentrations 20 μm from the presynaptic release site following transmitter exocytosis from a synaptic vesicle containing 3,000 (black) or 10,000 molecules (magenta), corresponding to L-DOPA’s increase of quantal size in cultured midbrain neurons 25,26. The “spheres of influence”, i.e., the volume around the release sites where DA concentrations are > 10 nM, were as follows. A: 3,000 molecules, r = 12 μm, 7,200 μm3 (100 %); 10,000 molecules, r = 18 μm, 24,400 μm3 (338 %). B: 3,000 molecules, r = 21 μm, 38,800 μm3 (536 %); 10,000 molecules, r = 32 μm, 137,300 μm3 (1896 %). Tutorials on this random walk analysis and spreadsheets with the simulation can be downloaded from http://sulzerlab.org/download.html.