Nerve growth factor induces systemic hyperalgesia after thoracic burn injury in the rat.

Acute burn injury is usually associated with pain in the injured and nearby areas. However, we have recently reported that a thoracic scald induces hindpaw hyperalgesia during the healing stage in rats. The present study investigated the cause of the remotely occurring hyperalgesia. Behavioral testing using the von Frey test revealed that rats developed hyperalgesia in the neck and flank as well as the hindpaw 2-3 weeks after injury. The concentration of nerve growth factor (NGF) in the skin of the chest increased markedly during the healing stage. Moreover, rats injected daily with anti-NGF serum after burn injury did not develop hyperalgesia, suggesting that increased NGF in the tissue of the healing skin is a key factor causing systemic hyperalgesia during the recovery stage.