Lateral lamina V projection neuron axon collaterals connect sensory processing across the dorsal horn of the mouse spinal cord

• Published in: Scientific reports Vol. 14; no. 1; pp. 26354 - 22
• Main Authors: Browne, Tyler J., Smith, Kelly M., Gradwell, Mark A., Dayas, Christopher V., Callister, Robert J., Hughes, David I., Graham, Brett A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2024; Nature Publishing Group; Nature Portfolio
• Subjects: 631/1647/2253; 631/378; 631/378/3917; 631/443/376; 692/698/1688/1366; Animals; Axon collaterals; Axons; Axons - physiology; Cell activation; Cell body; Dorsal horn; Female; Humanities and Social Sciences; Information processing; Interneurons; Interneurons - physiology; Male; Mice; multidisciplinary; Optogenetics; Posterior Horn Cells - physiology; Science; Science (multidisciplinary); Sensory integration; Sensory neurons; Sensory perception; Signal processing; Signal transduction; Spinal cord; Spinal Cord - physiology; Spinal Cord Dorsal Horn - cytology; Spinal Cord Dorsal Horn - physiology; Substantia alba
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-73620-4

Spinal projection neurons (PNs) are defined by long axons that travel from their origin in the spinal cord to the brain where they relay sensory information from the body. The existence and function of a substantial axon collateral network, also arising from PNs and remaining within the spinal cord, is less well appreciated. Here we use a retrograde viral transduction strategy to characterise a novel subpopulation of deep dorsal horn spinoparabrachial neurons. Brainbow assisted analysis confirmed that virally labelled PN cell bodies formed a discrete cell column in the lateral part of Lamina V (LV lat ) and the adjoining white matter. These PNs exhibited large dendritic territories biased to regions lateral and ventral to the cell body column and extending considerable rostrocaudal distances. Optogenetic activation of LV Lat PNs confirmed this population mediates widespread signalling within spinal cord circuits, including activation in the superficial dorsal horn. This signalling was also demonstrated with patch clamp recordings during LV Lat PN photostimulation, with a range of direct and indirect connections identified and evidence of a postsynaptic population of inhibitory interneurons. Together, these findings confirm a substantial role for PNs in local spinal sensory processing, as well as relay of sensory signals to the brain.