Objective. To investigate the properties of voltage-gated sodium （Na+） channels in developing auditory neurons during early postnatal stages in the mammalian central nervous system.Methods. Using the whole-cell voltage-clamp technique

we have studied changes in the electrophysi-ological properties of Na+ channels in the principal neurons of the medial nucleus of the trapezoid body （MNTB）.Results. We found that MNTB neurons already express functional Na+ channels at postnatal day 1 （P1）

and that channel density begins to increase at P5 when the neurons receive synaptic innervation and reach its maximum （

3

fold） at P11 when functional hearing onsets. These changes were paralleled by an age-dependent acceleration in both inactivation and recovery from inactivation. In contrast

there was very little alteration in the voltage-dependence of inactivation.Conclusion. These profound changes in the properties of voltage-gated Na+ channels may increase the excitability of MNTB neurons and enhance their phase-locking fidelity and capacity during high-frequency synaptic transmission.