Intraspinal sprouting after administration of nerve growth factor antibodies to neonatal rats.

Previous observations show that neonatal removal of nerve growth factor results in an increased number of fine dorsal root axons in the adult animal. The present study shows that the same treatment results in 49% more axons in the adult tract of Lissauer, which is an area of spinal white matter that contains predominantly fine primary afferent axons. These data are consistent with the idea that postnatal removal of NGF leads to increased numbers of fine primary afferent axons which then pass into the white matter of the spinal cord and there make synaptic contacts. If so, this would be a useful preparation for studies on the mechanisms by which newly formed sensory axons can be induced to enter the spinal cord postnatally.