The role of voltage-sensitive dendritic conductances in generating bistable firing patterns in motoneurons

Motoneurons receive a dense innervation from fibers that descend from the brainstem and release the monoamines serotonin and noradrenalin. When monoamines are present, motoneurons can produce plateau potentials, which are sustained depolarizations that outlast a brief excitatory input. During voltage clamp, steady monosynaptic input from Ia afferents produced a current that persisted after the Ia input ceased. The likely origin of this current was in dendritic regions, where plateau potential channels were probably activated due to the lack of voltage clamp control during the synaptic input. The functional significance of these data is discussed.