title: A group of segmental premotor interneurons regulates the speed of axial locomotion in Drosophila larvae.
abstract: BACKGROUND
  Animals control the speed of motion to meet behavioral demands. Yet, the underlying neuronal mechanisms remain poorly understood. Here we show that a class of segmentally arrayed local interneurons (period-positive median segmental interneurons, or PMSIs) regulates the speed of peristaltic locomotion in Drosophila larvae.
  
  
  RESULTS
  PMSIs formed glutamatergic synapses on motor neurons and, when optogenetically activated, inhibited motor activity, indicating that they are inhibitory premotor interneurons. Calcium imaging showed that PMSIs are rhythmically active during peristalsis with a short time delay in relation to motor neurons. Optogenetic silencing of these neurons elongated the duration of motor bursting and greatly reduced the speed of larval locomotion.
  
  
  CONCLUSIONS
  Our results suggest that PMSIs control the speed of axial locomotion by limiting, via inhibition, the duration of motor outputs in each segment. Similar mechanisms are found in the regulation of mammalian limb locomotion, suggesting that common strategies may be used to control the speed of animal movements in a diversity of species.
authors.affiliation: Department of Physics, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kohsaka
authors.affiliation: Department of Physics, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Takasu
authors.affiliation: Laboratory of Cellular Neurobiology, School of Life Sciences, Tokyo University of Pharmacy and Life Science, Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Morimoto
authors.affiliation: Department of Physics, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan. Electronic address: nose@k.u-tokyo.ac.jp.
authors.forename: Akinao
authors.initials: A
authors.lastname: Nose
mesh_terms: D000200:Action Potentials; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D004330:Drosophila / Q000166:cytology / Q000502:physiology*; D007814:Larva / Q000166:cytology / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*