Modeling inhibitory and excitatory effect of astroglia in synaptic plasticity and learning

Unlike past, scientific researches in recent years have shown that glial cells actively play various important roles in the nervous system. Because of difficulty in experimental study of glia a suitable method to investigate various aspects of its function is mathematical modeling. In this paper we attempt to illustrate inhibitory and excitatory aspects of astrocyte cells in producing Central Pattern Generators (CPG) and predict their role in some diseases by using modeling approach. We extracted CPG model from biological based data and then modeled sensitivity of glia cell to changes of the potassium equilibrium (a parameter), effect of synaptic activation on the secondary messenger production (inositol 1, 4, 5-trisphosphate (IP3)) (β parameter), Increasing [Ca²⁺] in the glial cytoplasm triggers the production of a mediator (glutamate) and its release into the intercellular space (d parameter) and effect of glial mediator (glutamate and adenosine 5´-triphosphate (ATP)) on postsynaptic neuron (γ and η respectively). To evaluate the model, first a simple 2 layer neural astrocyte network was simulated. Then results were compared with experimental evidence. Analysis of the waveforms showed the effect of astrocyte cell in modulating the synaptic transmission especially generation of patterns of rhythmic signals that can be used as CPG, changing neural network structure, acquisition of memory via impulse repetition which may be considered as long-term potentiation (LTP). We propose that glia have important effect on optimal intrinsic subthreshold oscillations (ISO) functionality. Finally, the model predicted the effects of astrocyte in some neurological disorders.