title: Identification of excitatory premotor interneurons which regulate local muscle contraction during Drosophila larval locomotion.
abstract: We use Drosophila larval locomotion as a model to elucidate the working principles of motor circuits. Larval locomotion is generated by rhythmic and sequential contractions of body-wall muscles from the posterior to anterior segments, which in turn are regulated by motor neurons present in the corresponding neuromeres. Motor neurons are known to receive both excitatory and inhibitory inputs, combined action of which likely regulates patterned motor activity during locomotion. Although recent studies identified candidate inhibitory premotor interneurons, the identity of premotor interneurons that provide excitatory drive to motor neurons during locomotion remains unknown. In this study, we searched for and identified two putative excitatory premotor interneurons in this system, termed CLI1 and CLI2 (cholinergic lateral interneuron 1 and 2). These neurons were segmentally arrayed and activated sequentially from the posterior to anterior segments during peristalsis. Consistent with their being excitatory premotor interneurons, the CLIs formed GRASP- and ChAT-positive putative synapses with motoneurons and were active just prior to motoneuronal firing in each segment. Moreover, local activation of CLI1s induced contraction of muscles in the corresponding body segments. Taken together, our results suggest that the CLIs directly activate motoneurons sequentially along the segments during larval locomotion.
authors.affiliation: Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Hasegawa
authors.affiliation: Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, The United States of America.
authors.forename: James W
authors.initials: JW
authors.lastname: Truman
authors.affiliation: Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, Japan.|Department of Physics, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Akinao
authors.initials: A
authors.lastname: Nose
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004330:Drosophila / Q000502:physiology*; D007395:Interneurons / Q000502:physiology*; D007814:Larva / Q000502:physiology*; D008124:Locomotion; D008954:Models, Biological; D009044:Motor Cortex / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D010528:Peristalsis
chemical_list: D002118:Calcium