ABSTRACT
Nerve damage due to trauma or disease often leads to chronic pain, for reasons that are poorly understood. Animal models of peripheral neuropathy have been developed in which the mechanisms underlying hyperalgesia due to nerve injury can be analysed. Nerve growth factor (NGF) is best known for its role in protecting certain classes of neurons from cell death during development. Subcutaneous injection of nerve growth factor into the hindpaws of normal rats resulted in hyperalgesia in response to both mechanical and thermal stimuli. In rats with hyperalgesia resulting from partial ligation of the sciatic nerve, significant relief of mechanical and thermal hyperalgesia was produced by intraperitoneal injection of antiserum against NGF. Degranulation was confirmed by comparing the histological profiles of mast cells in the sciatic nerves of treated and control rats. In the periphery, nerve injury would lead to elevated levels of NGF, presumably in the injured nerve or in the skin that it innervates.
