title: Action potential generation at an axon initial segment-like process in the axonless retinal AII amacrine cell.
abstract: In axon-bearing neurons, action potentials conventionally initiate at the axon initial segment (AIS) and are important for neuron excitability and cell-to-cell communication. However in axonless neurons, spike origin has remained unclear. Here we report in the axonless, spiking AII amacrine cell of the mouse retina a dendritic process sharing organizational and functional similarities with the AIS. This process was revealed through viral-mediated expression of channelrhodopsin-2-GFP with the AIS-targeting motif of sodium channels (Na(v)II-III). The AII processes showed clustering of voltage-gated Na+ channel 1.1 (Na(v)1.1) as well as AIS markers ankyrin-G and neurofascin. Furthermore, Na(v)II-III targeting disrupted Na(v)1.1 clustering in the AII process, which drastically decreased Na+ current and abolished the ability of the AII amacrine cell to generate spiking. Our findings indicate that, despite lacking an axon, spiking in the axonless neuron can originate at a specialized AIS-like process.
authors: Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
authors: Chaowen
authors: C
authors: Wu
authors: Elena
authors: E
authors: Ivanova
authors: Jinjuan
authors: J
authors: Cui
authors: Qi
authors: Q
authors: Lu
authors: Zhuo-Hua
authors: ZH
authors: Pan
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D025042:Amacrine Cells / Q000145:classification / Q000166:cytology*; D000818:Animals; D017487:Ankyrins / Q000378:metabolism; D000075402:Channelrhodopsins; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003712:Dendrites / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D062550:NAV1.1 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation / Q000379:methods; D012160:Retina / Q000166:cytology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: C094681:Ank3 protein, mouse; D017487:Ankyrins; D000075402:Channelrhodopsins; D062550:NAV1.1 Voltage-Gated Sodium Channel; C549200:Nav2 protein, mouse; D009419:Nerve Tissue Proteins; C568249:Scn1a protein, mouse; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D049452:Green Fluorescent Proteins; D013779:Tetrodotoxin; D003577:Cytochrome P-450 Enzyme System