Segmental Organization of Vestibulospinal Inputs to Spinal Interneurons Mediating Crossed Activation of Thoracolumbar Motoneurons in the Neonatal Mouse

• DOI: 10.1523/jneurosci.5188-14.2015
• Publication Date: 2015-05-27T18:18:15Z
• Authors: Nedim Kasumacic; François M. Lambert; Patrice Coulon; Helene Bras; Laurent Vinay; Marie-Claude Perr...; Joel C. Glover
• Keywords: Commissure; Lumbar Spinal Cord; Hindlimb; Decerebrate State; Lateral vestibular nucleus

Vestibulospinal pathways activate contralateral motoneurons (MNs) in the thoracolumbar spinal cord of neonatal mouse exclusively via axons descending ipsilaterally from vestibular nuclei lateral vestibulospinal tract (LVST; Kasumacic et al., 2010). Here we investigate how transmission LVST to MNs is mediated by commissural interneurons (dCINs) different segments. We test polysynaptic nature this crossed projection assessing LVST-mediated ventral root (VR) response latencies, manipulating synaptic responses pharmacologically, and tracing pathway transynaptically hindlimb extensor muscles using rabies virus (RV). Longer latencies than ipsilateral VRs, near-complete abolition calcium mephenesin, absence transsynaptic RV labeling neurons within a monosynaptic time window all indicate an overwhelmingly MNs. Optical recording synaptically identifies LVST-responsive dCINs that exhibit segmental differences proportion dorsoventral distribution. In contrast thoracic lower lumbar segments, which most are responsive, upper segments stand out because they contain much smaller more ventrally restricted subpopulation dCINs. A large these project L5, contains many activated LVST. selective channeling inputs through segmentally dorsoventrally subsets provides mechanism for targeting signals differentially trunk mammalian cord.