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Persistent inward Ca2+ and Na+ currents (PICs) may cause plateau potentials and they are part of the intrinsic properties of spinal motoneurons.Studies in cats and rats have shown that after acute spinal cord transection the motoneurons lose their ability to generate plateau potentials due to the loss of descending monoaminergic actions.However,the plateau properties do recover after several weeks without the return of monoaminergic innervation.In rats the return of plateau properties-in parallel with the development of spasticity-have been studied in tail motoneurons following chronic sacral spinal transection.The voltage-gated L-type Ca2+ channel Cav1.3 (mediating the Ca2+-PICs) is expressed in majority of the spinal neurons.Although no specific Na+ channel was specified to mediate the Na+-PICs,voltage-gated Na+ channel Nav1.3 has been observed to be significantly upregulated in spinal dorsal horn neurons 1 month after contusion injury and might be implicated for the hyperexcitability of the dorsal horn neurons.