Following Spinal Cord Injury Transected Reticulospinal Tract Axons Develop New Collateral Inputs to Spinal Interneurons in Parallel with Locomotor Recovery

Figure 1

Experiment timeline and STAG SCI model. The timeline is shown in (a). The RtST was anterogradely traced with BDA, and PrINs were retrogradely traced with TMR (b). (c) shows a detailed view of the two SCIs and intact tissue bridge and outlines some of the possible reticulo-propriospinal pathways that could circumvent the SCIs to allow descending input from the RtST to lumbar motor systems. Areas of the spinal cord which are shaded dark grey correspond to the intended injuries. The CST and RtST appear in yellow and green, respectively. Traced RtST axons are shown descending in the white matter of the unlesioned hemicord at T7 (green; (c)) and stopping once reaching the second injury at T10. We hypothesize that injured RtST axons could project collaterals into the grey matter and form contacts with PrINs (red; (c)) that would then carry the signal to motor neurons (purple; (c)) below the SCIs. White dashed line, outline of cross-section. Red dashed line, gigantocellular reticular nucleus. Yellow dashed line, outline of lumbar grey matter. Scale bar = 1000 μm.

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