Figure 8.

Axotomy-induced recombination one week following spinal hemisection: spinal cord. A, Two examples of the injury site from separate animals in longitudinal section. Insets show consistently-recombining ipsilaterally-projecting neurons near Clarke’s column below the injury. B, Cartoon of transverse section of the hemisected spinal cord illustrating relative positions of positionally and morphologically distinguishable recombined neurons (colored dots correspond to examples in C–F). C, Examples of recombination after injury in cervical (top left), lumbar (two examples middle and bottom-left), and thoracic (top right). The most consistent findings were small ipsilaterally-projecting neurons in the thoracic cord (C’), and large neurons contralateral to injury from just lateral to area X to the ventral gray matter in the lumbar cord (C’’). Arrows in C’, C’’ indicate midline-crossing axons. Arrow pointing to tdtomato⁺ axons in dorsal cervical white matter indicates probable rubrospinal (RST) and/or raphespinal tracts. Arrows pointing to reporter-positive axons in ventral white matter indicate probable reticulospinal (RtST) and vestibulospinal (VST), and an unknown descending projection (?) tracts rostral to the injury, and spinothalamic (STT) and possible dorsal spinocerebellar [DSCT(?)] below the injury (thoracic and lumbar sections). D, Neurons in Clarke’s column ipsilateral to the hemisection. E, F, Large and small, respectively, putative spinothalamic tract neurons contralateral to the hemisection. Arrows in E, F indicate commissural axons; cc, central canal.