Anatomical and Molecular Properties of Long Descending Propriospinal Neurons in Mice

• Published in: Frontiers in neuroanatomy Vol. 11; p. 5
• Main Authors: Flynn, Jamie R, Conn, Victoria L, Boyle, Kieran A, Hughes, David I, Watanabe, Masahiko, Velasquez, Tomoko, Goulding, Martyn D, Callister, Robert J, Graham, Brett A
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Research Foundation 06-02-2017; Frontiers Media S.A
• Subjects: Artificial chromosomes; Brain research; Cell body; Cytology; Interneurons; Locomotion; Medical research; Morphology; Neurons; Neuroscience; Neurosciences; Phenotypes; Presynapse; Provenance; Recovery of function; Rodents; Spatial distribution; Spinal cord; Spinal cord injuries; Substantia grisea; Thorax; Transgenic animals; Transgenic mice; Australia; United States > US; propriospinal; developmental genetics; neuroanatomy; synapse; morphology; inhibitory
• ISSN: 1662-5129; 1662-5129
• DOI: 10.3389/fnana.2017.00005

Long descending propriospinal neurons (LDPNs) are interneurons that form direct connections between cervical and lumbar spinal circuits. LDPNs are involved in interlimb coordination and are important mediators of functional recovery after spinal cord injury (SCI). Much of what we know about LDPNs comes from a range of species, however, the increased use of transgenic mouse lines to better define neuronal populations calls for a more complete characterisation of LDPNs in mice. In this study, we examined the cell body location, inhibitory neurotransmitter phenotype, developmental provenance, morphology and synaptic inputs of mouse LDPNs throughout the cervical and upper thoracic spinal cord. LDPNs were retrogradely labelled from the lumbar spinal cord to map cell body locations throughout the cervical and upper thoracic segments. Ipsilateral LDPNs were distributed throughout the dorsal, intermediate and ventral grey matter as well as the lateral spinal nucleus and lateral cervical nucleus. In contrast, contralateral LDPNs were more densely concentrated in the ventromedial grey matter. Retrograde labelling in
and
mice showed the majority of inhibitory LDPNs project either ipsilaterally or adjacent to the midline. Additionally, we used several transgenic mouse lines to define the developmental provenance of LDPNs and found that V2b positive neurons form a subset of ipsilaterally projecting LDPNs. Finally, a population of Neurobiotin (NB) labelled LDPNs were assessed in detail to examine morphology and plot the spatial distribution of contacts from a variety of neurochemically distinct axon terminals. These results provide important baseline data in mice for future work on their role in locomotion and recovery from SCI.