title: Gap Junction-Mediated Signaling from Motor Neurons Regulates Motor Generation in the Central Circuits of LarvalDrosophila.
abstract: In this study, we used the peristaltic crawling ofDrosophilalarvae as a model to study how motor patterns are regulated by central circuits. We built an experimental system that allows simultaneous application of optogenetics and calcium imaging to the isolated ventral nerve cord (VNC). We then investigated the effects of manipulating local activity of motor neurons (MNs) on fictive locomotion observed as waves of MN activity propagating along neuromeres. Optical inhibition of MNs with halorhodopsin3 in a middle segment (A4, A5, or A6), but not other segments, dramatically decreased the frequency of the motor waves. Conversely, local activation of MNs with channelrhodopsin2 in a posterior segment (A6 or A7) increased the frequency of the motor waves. Since peripheral nerves mediating sensory feedback were severed in the VNC preparation, these results indicate that MNs send signals to the central circuits to regulate motor pattern generation. Our results also indicate segmental specificity in the roles of MNs in motor control. The effects of the local MN activity manipulation were lost inshaking-B2(shakB2) orogre2, gap-junction mutations inDrosophila, or upon acute application of the gap junction blocker carbenoxolone, implicating electrical synapses in the signaling from MNs. Cell-type-specific RNAi suggestedshakBandogrefunction in MNs and interneurons, respectively, during the signaling. Our results not only reveal an unexpected role for MNs in motor pattern regulation, but also introduce a powerful experimental system that enables examination of the input-output relationship among the component neurons in this system.SIGNIFICANCE STATEMENTMotor neurons are generally considered passive players in motor pattern generation, simply relaying information from upstream interneuronal circuits to the target muscles. This study shows instead that MNs play active roles in the control of motor generation by conveying information via gap junctions to the central pattern-generating circuits in larvalDrosophila, providing novel insights into motor circuit control. The experimental system introduced in this study also presents a new approach for studying intersegmentally coordinated locomotion. Unlike traditional electrophysiology methods, this system enables the simultaneous recording and manipulation of populations of neurons that are genetically specified and span multiple segments.
authors.affiliation: Department of Complexity Science and Engineering, University of Tokyo, Chiba 277-8561, Japan and.
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Matsunaga
authors.affiliation: Department of Complexity Science and Engineering, University of Tokyo, Chiba 277-8561, Japan and.|Department of Physics, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Hiroshi
authors.identifier: 0000-0003-1087-9680
authors.initials: H
authors.lastname: Kohsaka
authors.affiliation: Department of Complexity Science and Engineering, University of Tokyo, Chiba 277-8561, Japan and nose@neuro.k.u-tokyo.ac.jp.|Department of Physics, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Akinao
authors.identifier: 0000-0002-0526-2128
authors.initials: A
authors.lastname: Nose
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002118:Calcium / Q000378:metabolism; D002229:Carbenoxolone / Q000494:pharmacology; D002490:Central Nervous System / Q000166:cytology / Q000502:physiology*; D017630:Connexins / Q000235:genetics / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D025602:Halorhodopsins / Q000378:metabolism; D066298:In Vitro Techniques; D007814:Larva / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009046:Motor Neurons / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009433:Neural Inhibition / Q000235:genetics; D062308:Optogenetics; D034622:RNA Interference / Q000502:physiology
chemical_list: D017630:Connexins; D029721:Drosophila Proteins; D025602:Halorhodopsins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C079326:ogre protein, Drosophila; C079324:shakB protein, Drosophila; D002229:Carbenoxolone; D002118:Calcium
keywords: Drosophila; calcium imaging; gap junctions; motoneurons; optogenetics; shakB