Un método híbrido (dinámica molecular / MonteCarlo) para modelar plasticidades sinápticas en células excitables

Abstract

Present work comprises a computational model to reproduce the dynamics of synaptic vesicles. An algorithm is developed and implemented to allow the study of synaptic plasticity resulting from the controlled fusion of synaptic vesicles in the presynaptic terminal. The presynaptic terminal is spatially modeled as a box located within the coordinate axis with the presynaptic membrane corresponding to the z=0 plane. Forces controlling changes of speed and position for each vesicle result from three sources: (1) Electric Fields originating from intracellular, extracellular and intravesicular medium [1] and from charges in the vesicular and presynaptic membranes. (2) Forces derived from the polarized water clathrate surrounding the synaptic vesicles. (3) Frictional forces derived from moving synaptic vesicles which are proportional to their speed [2]. Physical constants employed in the simulations were approximated to those reported for squid giant axon by other researchers. The size of the Synaptic Vesicles and the Terminal Box were also chosen from those reported by other researchers. Synaptic vesicles were incorporated into the terminal box by means of a predetermined sequence up to the point were the pool reached equilibrium. Once in equilibrium vesicular fusion probability was modulated to simulate periodic stimulation and response of the Synaptic Pool. Results obtain from the simulation are consistent with experimental results reported by other researchers, there fore validating the model.