Fetal locus coeruleus transplanted into the transected spinal cord of the adult rat.

Locus coeruleus tissue from 16-day-old fetal rats has been successfully transplanted into the transected spinal cord of the young adult female rat. During development, the solid tissue implant (approximately equal to 1.2 mm3) always breaks up into smaller cell clusters. Fluorescent axons from the fetal neurons invaded the host tissue, and grew for several millimeters away from the cell-body region. The damaged rostral noradrenergic axons in the ventral horn (projecting from the locus coeruleus) exhibited an intense proliferation in response to a neurotrophic factor produced by the fetal implant. Finally, in 2/8 cases, the axons of the fetal, noradrenergic locus coeruleus neurons remained confined to the fetal nuclear tissue. The results are discussed in the context of recent attempts to reconstruct the damaged mammalian spinal cord.