A COMPUTATIONAL MODEL WITH IONIC CONDUCTANCES FOR THE FUSIFORM CELL OF THE DORSAL COCHLEAR NUCLEUS

A computational model of a fusiform cell of the dorsal cochlear nucleu s was developed. The results of model simulations are compared with th e results of in vitro experimental observations obtained by other inve stigators. The structure of the present model is similar to that of Ho dgkin-Huxley [J. Physiol. 117, 500-544 (1952)]. The model incorporates five nonlinear voltage-dependent conductances (three potassium and tw o sodium types) and their associated equilibrium-potential batteries, a leakage conductance, the membrane capacitance, and a current source. Model responses were obtained under both current- and voltage-clamp c onditions. When a hyper- and depolarizing current sequence was applied [Manis, J. Neurosci. 10, 2338-2351 (1990)], the cell model was able t o reproduce builduplike and pauserlike discharge patterns closely rese mbling Manis' observations. A transient ''A''-type potassium conductan ce in the model played a major role in generating this phenomenon. The model predicts that blocking the ''A'' conductance should convert a b uilduplike or pauserlike pattern into a sustained regular pattern. A p ersistent sodium conductance in the model played the main role in repr oducing: Spontaneous regular discharges; a discharge after a long late ncy under a long small (+0.025 nA) current; and nonlinear voltage-curr ent characteristics with positive currents. Usefulness of the model ca n be seen as follows: (1) Several sets of experimental observations ca n be integrated into a common framework; (2) possible roles of differe nt ionic conductances postulated to be present in the cell can be infe rred by observing the model behavior with the conductances intact or b locked; and (3) time courses of ionic currents and conductance values obtained from the model under current- and voltage-clamp conditions ca n serve as predictions to be tested in future experimental studies.