Research article summary (published 14 Sep 2009):

Activity of Hb9 interneurons during fictive locomotion in mouse spinal cord.

Full Abstract

Hb9 interneurons (Hb9 INs) are putative components of the mouse spinal locomotor central pattern generator (CPG) and candidates for the rhythm-generating kernel. Studies in slices and hemisected spinal cords showed that Hb9 INs display TTX-resistant membrane potential oscillations, suggesting a role in rhythm generation. To further investigate the roles of Hb9 INs in the locomotor CPG, we used two-photon calcium imaging in the in vitro isolated whole neonatal mouse spinal cord preparation to record the activity of Hb9 INs, which were subsequently stained for unambiguous genetic identification. We elicited fictive locomotion by transmitter application or by electrically stimulating the caudal tip of the spinal cord. Although most Hb9 INs were rhythmically active during fictive locomotion, their activity was sparse and they failed to fire with each cycle of the episode. If Hb9 INs are the principal pacemakers of the CPG in the hemisegment in which they are located, they should direct the firing of motor neurons, with their activity preceding that of their ipsilateral segmental ventral roots. Instead, during each locomotor cycle, onset of Hb9 IN activity lagged behind the onset of the ipsilateral ventral root burst by a mean phase of 0.21 during electrical stimulation and 0.28 during transmitter application. Whole-cell recordings in intact and hemisected spinal cords confirmed the imaging results. Our data suggest that Hb9 INs participate in fictive locomotion, but the delayed onset of activity relative to ipsilateral motoneurons suggests that Hb9 INs are unlikely to be the sole intrasegmental rhythm-generating kernel of the CPG.

Author information

Author/s: Kwan, Alex C (AC); Dietz, Shelby B (SB); Webb, Watt W (WW); Harris-Warrick, Ronald M (RM);

Affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.

Grants: 9-P41-EB001976 (Agency:NIBIB NIH HHS)

Journal and publication information

Publication Type: In Vitro; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.

Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci), published in United States. (Language: eng)

Reference: 2009-Sep; vol 29 (issue 37) : pp 11601-13

Dates: Created 2009/09/17; Completed 2009/10/02; Revised 2009/10/05;

PMID: 19759307, status: MEDLINE (last retrieval date: 10/6/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Analysis of Variance Animals Behavior, Animal Calcium - metabolism Dopamine - pharmacology Electric Stimulation Functional Laterality Green Fluorescent Proteins - genetics Homeodomain Proteins - genetics; metabolism Interneurons - drug effects; physiology Locomotion - genetics; physiology Membrane Potentials - drug effects; genetics; physiology

Membrane Potentials - drug effects; genetics; physiology Mice Mice, Transgenic Motor Neurons - physiology N-Methylaspartate - pharmacology Neurotransmitter Agents - pharmacology Patch-Clamp Techniques - methods Serotonin - pharmacology Spinal Cord - cytology Spinal Nerve Roots - cytology; physiology Time Factors Transcription Factors - genetics; metabolism

Associated Chemicals: Homeodomain Proteins (0) ; Neurotransmitter Agents (0) ; Transcription Factors (0) ; Hb9 protein, mouse (140115-73-7) ; Green Fluorescent Proteins (147336-22-9) ; Serotonin (50-67-9) ; N-Methylaspartate (6384-92-5) ; Calcium (7440-70-2)

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