Injured tissues will release various substances, such as potassium, prostaglandins,
histamine, of bradykinins that are pronociceptive, and will also evoke an immune response.
7These inflammatory and immune factors will sensitize the nociceptive receptors directly
within the lesion and in the surrounding neurons. Primary hyperalgesia, which follows the
release of these factors, may be measured as a lowered pain threshold in and around the
lesion.