Receptor Diffusion & Cluster Model - ReDiClus Model
Diffusion and Cluster Model of LTP
Diffusion and Cluster Model of LTP
Model Space
- The model is simulated in a 3D space with the following parameters
- There is a 3D XYZ coordinate grid
- The X-Y plane has 60x60 area
- The X-Y plane consists of real numbers: -30 to +30
- The Z axis is only 2 levels: 0 and -1
- 0 represents the membrane surface
- -1 represents intracellular space
Particle Types
- There are 2 types of particles in the simulation
- 'Red' particle dots represent AMPA receptors
- Red dots can randomly diffuse anywhere on the X-Y plane
- Red dots only diffuse on the surface Z = 0
- 'Blue' particle dots represent PSD-95 molecules
- Blue dots are contained in predefined PSD areas and cannot leave
- Blue dots can exist at the surface Z = 0 or intracellularly Z = -1
two independent processes
- In this model, there are two independently occurring processes.
- 1. Blue dots can be expressed at the surface or internalized within their PSD area
- The Blue dot internalization/externalization rate properties are set by the Shouval cluster model equations.
- 2. Red dots diffuse on the X-Y plane with brownian motion
- Each Red dot has an initial step size randomly drawn from a normal distribution with a mean = 1 and sd = .2
- The step size for Red dots is dynamically altered when it's located in a PSD area
- In a PSD, the step size is reduced by a by some factor based on the number of Blue dots currently expressed at the surface of that PSD
- The more Blue dots at the surface, the more the step size is reduced
- The current step size function is:
- f(Rstep) = R * (10*(1 ⁄ Bn))
- where Rstep is the baseline Red dot step size
- where Bn is number of Blue dots currently expressed at the PSD surface
- Several screen shots of the dynamic graphs in the model
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Quantitative Review
Quantitative Physiology of the Dendrite
Choquet 2007 Real Time Receptor Diffusion
Choquet 2007 Real Time Receptor Diffusion Analysis
- The video represents a 10µm × 10µm section scaled to a 535px × 535px video.
- The analysis below documents one instance of Qdot diffusion, between the 6s-7s time points.
- This instance was chosen because of the clarity of motion and no Qdot flicker.
- The Qdot (center) moves from pixel location (X:291, Y:302) at 6.78s to (X:319, Y346) at 6.98s
- That is a distance of 52.2px in 200ms
- Qdot velocity: Qv ≈ 1µm ⁄ 200ms
- Note this diffusion rate of 5µm/s is 10-fold higher than the median diffusion rate reported above.
- An upper bound of 5µm/s means that receptors can move between synapses in fractions of a second.
Figures:
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Receptor Diffusion Rate Best Estimates
- GABAA: .01 - .05 µm2/s FIG: {{#info: Choquet 2010 CLICK AWAY FROM IMAGE TO CLOSE }}