The endogenous electrical field effect on pyramidal neural network with low calcium

It is known that low extracellular calcium can induces paroxysmal events that closely approximate epileptic activity and non-synaptic epileptiform activity can be induced by high potassium and low calcium solution in vivo in the hippocampal CA1 region when synaptic transmission is blocked. It has been suggested that tissue swelling, which occurs when the extracellular calcium is decreasing, increases the extracellular resistivity, and increases the strength of field effects in hippocampal slices. And during epileptic seizures, pathological field can be as strong as 100 millivolts per millimeter. Presumably, such strong fields may entrain neural firing and give rise to super-synchronized states. We, therefore, tested the hypothesis that ephaptic communication mode should induce epileptiform discharge under low calcium environment. The simulation results showed that 1) The firing frequency of neural network is significantly increased under a low calcium environment. 2) Endogenous electrical field can entrain neural firing and give rise to super-synchronized states under a low calcium environment. 3) Compared with normal environment, neural network can be synchronized in a relatively low coupling strength in an abnormal environment, such as low calcium environment. That´s to say, it is more sensitive to electrical field. 4) Whether in normal environment or abnormal environment, ephaptic transmission can always synchronize the neural network if the coupling strength is strong enough.