Computed potential responses of small cultured rat hippocampal neurons.

1. The potential responses of small hippocampal neurons were computed on the basis of a previous mathematical description of the currents recorded under voltage-clamp conditions. 2. The computed action potentials were graded with respect to stimulus strength, in accordance with previous experimental findings. 3. The time course of the membrane currents and of the permeabilities and permeability variables during the impulse was computed for different stimulus intensities. 4. The effect of the membrane time constant on the impulse amplitude was investigated. It was concluded that the value of the time constant used was not per se sufficient to explain the amplitude variation of the impulse. 5. The effect of the magnitudes of the different potential-dependent permeabilities on the impulse amplitude was investigated. A Na+ permeability within a certain range caused impulses of variable amplitude, and this variability was affected by the K+ permeability.