title: Slow integration leads to persistent action potential firing in distal axons of coupled interneurons.
abstract: The conventional view of neurons is that synaptic inputs are integrated on a timescale of milliseconds to seconds in the dendrites, with action potential initiation occurring in the axon initial segment. We found a much slower form of integration that leads to action potential initiation in the distal axon, well beyond the initial segment. In a subset of rodent hippocampal and neocortical interneurons, hundreds of spikes, evoked over minutes, resulted in persistent firing that lasted for a similar duration. Although axonal action potential firing was required to trigger persistent firing, somatic depolarization was not. In paired recordings, persistent firing was not restricted to the stimulated neuron; it could also be produced in the unstimulated cell. Thus, these interneurons can slowly integrate spiking, share the output across a coupled network of axons and respond with persistent firing even in the absence of input to the soma or dendrites.
authors.affiliation: Department of Neurobiology & Physiology, Northwestern University, Evanston, Illinois, USA.
authors.forename: Mark E J
authors.initials: ME
authors.lastname: Sheffield
authors.forename: Tyler K
authors.initials: TK
authors.lastname: Best
authors.forename: Brett D
authors.initials: BD
authors.lastname: Mensh
authors.forename: William L
authors.initials: WL
authors.lastname: Kath
authors.forename: Nelson
authors.initials: N
authors.lastname: Spruston
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology; D003712:Dendrites / Q000502:physiology; D006624:Hippocampus / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009415:Nerve Net / Q000502:physiology; D018408:Patch-Clamp Techniques; D013569:Synapses / Q000502:physiology