Purpose of this paper is to characterize the Ion-Sensitive Field-Effect Transistors (ISFET)-neuron junction, based on the equivalent electric-circuit approach. As a result, recording of action potentials can be simulated with a general-purpose circuit simulation program such as HSPICE. The neuronal electrical activity, extracellularly recorded by the ISFET, is analyzed as a function of the physical-chemical and geometric ISFET parameters, of the ionic currents in the neuron, and of the neuro-electronic junction parameters such as the sealing resistance, double-layer capacitance, and general adhesion conditions. The models of the neuron, of the coupling circuit, and of the ISFET implemented in HSPICE are first described. These models are then used to simulate the behavior of the junction between a patch of neuronal membrane (described by the compartmental model) and the ISFET.