title: Initiation of simple and complex spikes in cerebellar Purkinje cells.
abstract: Cerebellar Purkinje cells produce two distinct forms of action potential output: simple and complex spikes. Simple spikes occur spontaneously or are driven by parallel fibre input, while complex spikes are activated by climbing fibre input. Previous studies indicate that both simple and complex spikes originate in the axon of Purkinje cells, but the precise location where they are initiated is unclear. Here we address where in the axon of cerebellar Purkinje cells simple and complex spikes are generated. Using extracellular recording and voltage-sensitive dye imaging in rat and mouse Purkinje cells, we show that both simple and complex spikes are generated in the proximal axon, 15-20 mum from the soma. Once initiated, simple and complex spikes propagate both down the axon and back into the soma. The speed of backpropagation into the soma was significantly faster for complex compared to simple spikes, presumably due to charging of the somatodendritic membrane capacitance during the climbing fibre synaptic conductance. In conclusion, we show using two independent methods that the final integration site of simple and complex spikes is in the proximal axon of cerebellar Purkinje cells, at a location corresponding to the distal end of the axon initial segment.
authors.affiliation: Department of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
authors.forename: Lucy M
authors.initials: LM
authors.lastname: Palmer
authors.forename: Beverley A
authors.initials: BA
authors.lastname: Clark
authors.forename: Jan
authors.initials: J
authors.lastname: Gründemann
authors.forename: Arnd
authors.initials: A
authors.lastname: Roth
authors.forename: Greg J
authors.initials: GJ
authors.lastname: Stuart
authors.forename: Michael
authors.initials: M
authors.lastname: Häusser
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001369:Axons / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D011689:Purkinje Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar