title: Spatial dynamics of action potentials estimated by dendritic Ca(2+) signals in insect projection neurons.
abstract: The spatial dynamics of action potentials, including their propagation and the location of spike initiation zone (SIZ), are crucial for the computation of a single neuron. Compared with mammalian central neurons, the spike dynamics of invertebrate neurons remain relatively unknown. Thus, we examined the spike dynamics based on single spike-induced Ca(2+) signals in the dendrites of cricket mechanosensory projection neurons, known as giant interneurons (GIs). The Ca(2+) transients induced by a synaptically evoked single spike were larger than those induced by an antidromic spike, whereas subthreshold synaptic potentials caused no elevation of Ca(2+). These results indicate that synaptic activity enhances the dendritic Ca(2+) influx through voltage-gated Ca(2+) channels. Stimulation of the presynaptic sensory afferents ipsilateral to the recording site evoked a dendritic spike with higher amplitude than contralateral stimulation, thereby suggesting that alteration of the spike waveform resulted in synaptic enhancement of the dendritic Ca(2+) transients. The SIZ estimated from the spatial distribution of the difference in the Ca(2+) amplitude was distributed throughout the right and left dendritic branches across the primary neurite connecting them in GIs.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan. Electronic address: hogawa@sci.hokudai.ac.jp.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Ogawa
authors.affiliation: Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Ruriko
authors.initials: R
authors.lastname: Mitani
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D006135:Gryllidae / Q000502:physiology*; D019476:Insect Proteins / Q000378:metabolism; D007395:Interneurons / Q000166:cytology / Q000502:physiology*; D008297:Male; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D055366:Synaptic Potentials / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D015220:Calcium Channels; D019476:Insect Proteins; D002118:Calcium
keywords: Calcium imaging; Dendrite; Insect neuron; Laterality; Spike initiation zone; Spike propagation