Selective Corticospinal Tract Injury in the Rat Induces Primary Afferent Fiber Sprouting in the Spinal Cord and Hyperreflexia

This study investigates how damage to the corticospinal tract (CST), a major brain pathway controlling voluntary movement, affects nerve connections in the spinal cord. Researchers severed the CST in rats and examined changes in other nerve fibers. They found that after CST injury, sensory nerve fibers called proprioceptive afferents, which provide information about body position, sprouted into areas of the spinal cord that had lost connections due to CST damage. These changes may contribute to muscle stiffness or spasms (spasticity). The study suggests that injury to the CST causes a reorganization of nerve connections in the spinal cord, leading to increased sensitivity of reflexes and potentially contributing to movement problems.

• 1
  Selective CST injury induces proprioceptive afferent plasticity in the spinal cord, leading to sprouting of afferent fibers into denervated gray matter regions.
• 2
  There was an increase in VGlut1-positive boutons, indicative of group 1A afferent terminals, on motoneurons after PTx, suggesting increased excitatory input onto motoneurons.
• 3
  Pyramidotomy increased microglia density in the spinal cord gray matter, particularly in regions where CST terminations were lost, suggesting a microglial response to CST injury.