Modeling of evoked field potentials in hippocampal CA1 area describes their dependence on NMDA and GABA receptors

A computer model of the hippocampal CA1 area, which receives synaptic inputs from CA3 neurons via the Schaffer collaterals, was constructed. Pyramidal cells (PC) and two types of interneurons were represented by compartmental models, and mechanisms of feed-forward inhibition (FFI) and recurrent inhibition were incorporated. Four types of receptor mediated synaptic conductances were used in the model: those of AMPA, GABA(A), GABA(B) and N-methyl-D-aspartate (NMDA). The output of the model, i.e. the field potential calculated at various points in space, was able to qualitatively reproduce the main features of field potentials, which were recorded in hippocampal slices maintained in vitro for both subthreshold and suprathreshold stimulation. In both the experiments and the model, the influence of NMDA and GABA synaptic currents affected mostly the late, decaying phase of evoked field potentials. The modeled interaction of NMDA and GABA components could explain the enhancement of the field potential late phase, which was observed experimentally during paired-pulse stimulation.