FHF-independent conduction of action potentials along the leak-resistant cerebellar granule cell axon.

Neurons in vertebrate central nervous systems initiate and conduct sodium action potentials in distinct subcellular compartments that differ architecturally and electrically. Here, we report several unanticipated passive and active properties of the cerebellar granule cell's unmyelinated axon. Whereas spike initiation at the axon initial segment relies on sodium channel (Na)-associated fibroblast growth factor homologous factor (FHF) proteins to delay Na inactivation, distal axonal Nas show little FHF association or FHF requirement for high-frequency transmission, velocity and waveforms of conducting action potentials.

Computational modeling predicts the ionic mechanism of late-onset responses in unipolar brush cells.

Unipolar Brush Cells (UBCs) have been suggested to play a critical role in cerebellar functioning, yet the corresponding cellular mechanisms remain poorly understood. UBCs have recently been reported to generate, in addition to early-onset glutamate receptor-dependent synaptic responses, a late-onset response (LOR) composed of a slow depolarizing ramp followed by a spike burst (Locatelli et al., 2013).