title: Identification of minimal neuronal networks involved in flexor-extensor alternation in the mammalian spinal cord.
abstract: Neural networks in the spinal cord control two basic features of locomotor movements: rhythm generation and pattern generation. Rhythm generation is generally considered to be dependent on glutamatergic excitatory neurons. Pattern generation involves neural circuits controlling left-right alternation, which has been described in great detail, and flexor-extensor alternation, which remains poorly understood. Here, we use a mouse model in which glutamatergic neurotransmission has been ablated in the locomotor region of the spinal cord. The isolated in vitro spinal cord from these mice produces locomotor-like activity-when stimulated with neuroactive substances-with prominent flexor-extensor alternation. Under these conditions, unlike in control mice, networks of inhibitory interneurons generate the rhythmic activity. In the absence of glutamatergic synaptic transmission, the flexor-extensor alternation appears to be generated by Ia inhibitory interneurons, which mediate reciprocal inhibition from muscle proprioceptors to antagonist motor neurons. Our study defines a minimal inhibitory network that is needed to produce flexor-extensor alternation during locomotion.
authors.affiliation: Mammalian Locomotor Laboratory, Department of Neuroscience, Karolinska Institutet, Stockholm S-17177, Sweden.
authors.forename: Adolfo E
authors.initials: AE
authors.lastname: Talpalar
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Endo
authors.forename: Peter
authors.initials: P
authors.lastname: Löw
authors.forename: Lotta
authors.initials: L
authors.lastname: Borgius
authors.forename: Martin
authors.initials: M
authors.lastname: Hägglund
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Dougherty
authors.forename: Jesper
authors.initials: J
authors.lastname: Ryge
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hnasko
authors.forename: Ole
authors.initials: O
authors.lastname: Kiehn
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D018756:GABA Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D018684:Glycine Agents / Q000494:pharmacology; D007395:Interneurons / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009415:Nerve Net / Q000033:anatomy & histology* / Q000502:physiology*; D010507:Periodicity; D010852:Picrotoxin / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000378:metabolism; D018009:Receptors, Glycine / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D013331:Strychnine / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D018756:GABA Antagonists; D018698:Glutamic Acid; D005998:Glycine; D018684:Glycine Agents; D010852:Picrotoxin; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; D013331:Strychnine; D050599:Vesicular Glutamate Transport Protein 2; D005680:gamma-Aminobutyric Acid; C493477:Slc17a6 protein, mouse