Dopamine release, diffusion and uptake: A computational model for synaptic and volume transmission
Fig 3
Single DA release event from synaptic terminal.
For all plots the initial baseline concentration was 4nM except in B & D where the inital baseline concentration was 50nM. A-D: Release of 3000 DA molecules from synaptic terminal. White isolines indicate the concentration of 10, 100 and 1000nM. All color scales represent concentration in μM. DA quickly escapes the synaptic cleft in scenarios without uptake (A & B) and also with volume (homogeneous) uptake (C & D). E: Detail of plot C with additional isolines of 10, 100 and 1000nM for simulations with a combination of volume and surface uptake (inhomogeneous uptake). White isolines refer to the simulation with volume uptake only. Gray and black isolines refer to the simulation where surface uptake was five and one-hundred times elevated, resp. Neither homogeneous uptake nor uptake strongly pronounced at the pre-synaptic terminal can prevent synaptic spillover. F: Concentration difference between simulations of homogeneous (white) and inhomogeneous uptake with five (gray) and one-hundred (black) times elevated uptake at the pre-synaptic terminal. G: Fast D2 receptor binding at different distances from release site. Comparable receptor binding occurs at distances up to 0.5μm. The blue and yellow graph are equivalent. D2R binding at half the distance of neighboring terminals (2.0μm) is still profound but negligible at 4.0μM. Differences between a synaptic (solid line) and a non-synaptic terminal (dashed line) could not be confirmed. H: Slow D2 receptor binding at different distances from release site for a synaptic (solid line) and a non-synaptic terminal (dashed line). Elevated receptor binding occurs at a distance of 0.1μm, (i.e. inside the synapse for the synaptic terminal with radius = 0.15μm), but not at distances beyond 0.2μm. D2R binding beyond half the distance of neighboring terminals (2.0μm) is small and negligible at 4.0μm.