Reaction-diffusion Coupling in a Structured System: Application to the Quantitative Simulation of Endplate Currents

An approach derived from reaction-diffusion problems is introduced to describe the synaptic endplate current (EPC) at the neuromuscular junction. The model constructed borrows heavily from earlier models, but it takes into account the anisotropic distribution of the different elements participating to the generation of EPC. The transmitter acetylcholine (ACh) is released at the presynatic membrane, diffuses through the cleft where acetylcholinesterase is homogeneously distributed and then reaches the postsynaptic surface where the receptor is located. The system is defined by a series of partial differential equations which are solved by an explicit difference method. The model predicts amplitudes and time constants in agreement with those observed experimentally, in all the conditions of inhibition of the enzyme or the receptor tested.