An ionic current model has been developed for the rat medial nucleus tractus solitarius (mNTS) neuron that provides a quantitative description of the ionic macrocurrents present in the soma of the cell, and their interaction in the genesis of patterned electrical activity. It consists of two parts, a model of the somatic membrane, and a fluid compartment model of the intra- and extracellular media. The somatic membrane model is of Hodgkin-Huxley form, and includes mathematical descriptions of time- and voltage-dependent ion selective channels, as well as pump, exchanger and other background currents present in the generic mNTS neuron. The lumped fluid compartment model accounts for intracellular changes in the Ca\sp2+ concentration. The model is able to successfully mimic the response of the neuron to different sequences of depolarizing and hyperpolarizing pulses, and has provided useful insights into the biophysical interactions underlying the phenomena of delayed excitation (DE) and spike frequency adaptation (SFA).