Obreja O, et al. - Individuals experience local hyperalgesia to mechanical and electrical stimuli lasting for weeks on receiving injection of nerve growth factor (NGF). In 11 human subjects, researchers recorded single C-nociceptors 3 weeks after intracutaneous injection of 1 μg NGF into the foot dorsum. Findings revealed that a combination of sensory sensitization and axonal hyperexcitability was underlying the localized hyperalgesia by facilitating action potential generation and conduction. In the asymptomatic skin surrounding the NGF-treatment sites, axonal changes were also found, thereby possibly reflecting “nociceptive priming.”