Increased numbers of thoracic dorsal root axons in rats given antibodies to nerve growth factor.

Sensory axons were counted in untreated 1-month-old rats and in littermates that were injected with antibodies to nerve growth factor. There were 45 percent more unmyelinated and 17 percent more myelinated axons in dorsal roots of the fifth thoracic spinal segment in treated rats. This suggests that the number of sensory axons can be changed by postnatal inactivation of nerve growth factor.