FIG. 3.

The impact of potassium and chloride ion concentrations on regular spiking (RS) neuronal firing and depolariziaton block. (A) The membrane potential of the RS neuron model under normal physiological levels of extracellular potassium and intracellular chloride is shown in the lower panel. The cell maintains a low firing rate, with occasional spikes driven by the stochastic synaptic inputs. The precise values of extracellular potassium and intracellular chloride are shown in the upper panel. (B) Same as in A, but for high extracellular potassium conditions similar to those seen during epileptic seizures. Note the increase in firing rate as a function of increased extracellular potassium. (C) Same as in A, but for high extracellular potassium plus high intracellular chlroide conditions similar to those seen after a traumatic brain injury. The cell first increases its firing rate, but then enters depolariziation block under these conditions. (D) Median membrane potential of the RS neuron model as a function of both extracellular potassium and intracellular chloride. (E) Same as in D, but for firing rate of the RS neuron model. Note the lack of firing in the upper right quadrant, corresponding to depolariziaton block of the RS neuron under high extracellular potassium and high intracellular chloride conditions.