Postnatal Changes in Electrophysiological Properties of Rat Jaw-Closing Motoneurons

The electrophysiological properties of jaw-closing motoneurons (JCMNs) in postnatally developing rats aged 4 to 27 days were investigated in slice preparations using intracellular recording techniques. The input resistance of JCMNs from young rats (aged 4-9 days) was greater than that of JCMNs from rats aged 10 days or older. The action potential half-duration progressively decreased with age. The incidence of post-spike afterdepolarization (ADP) progressively increased during postnatal development, whereas the amplitude and half-duration of the medium-duration afterhyperpolarization (mAHP) decreased with age. These findings demonstrate that in rat JCMNs, the input resistance, action potential, ADP and mAHP change during postnatal development. These changes are likely to affect the firing properties of JC-MNs.