The effects of nerve growth factor and its antibodies on axonal numbers in the medial gastrocnemius nerve of the rat

The effects of the administration of nerve growth factor (NGF) or its antibody (anti-NGF) on axonal populations in a peripheral nerve have been investigated. The nerve is a motor nerve, the nerve to the medial gastrocnemius muscle in the rat. The findings are that the administration of NGF at birth and for 28 days thereafter results in an increase of 42% of the unmyelinated axons in this nerve as compared to normal, and that the administration of anti-NGF in the same way results in a 20 and 30% decrease, respectively, in the myelinated and unmyelinated axons in this nerve. We speculate that the unmyelinated axon increase after NGF administration indicates an increase in post-ganglionic sympathetic axons and that the decreases in myelinated and unmyelinated axons after anti-NGF administration indicate decreases in both post-ganglionic sympathetic and sensory axons. The implications of these findings are discussed.