Plateau potentials and their role in regulating motoneuronal firing.

The classical view of the mammalian spinal motoneurone, which emerged from the laboratories of Eccles and Granit in the 1950s and 1960s, held that the cell membrane was essentially passive in areas of synaptic contact (largely the dendrites). The relation between the synaptic excitation and firing frequency was then determined by the post-spike afterhyperpolarisation (Granit and Kernell in the 1960s). During the last 15 years, it has been known that several active membrane properties, including voltage-dependent, non-inactivating inward currents, further shape the motoneuronal output. These inward currents may produce prolonged depolarizations (plateau potentials). It has been demonstrated that neurotransmitters can modify both the plateau properties and the afterhyperpolarisation, thus effectively controlling the input-output relation for the motoneurones.