Figure 1From: Increase of nerve growth factor levels in the human herniated intervertebral disc: can annular rupture trigger discogenic back pain?Protein levels of nerve growth factor (NGF) measured using ELISA in herniated and non-herniated discs. Data from the ELISA were normalized by total protein concentrations (pg/mg total protein). Mean values are indicated by short horizontal lines. The NGF level was significantly higher in herniated discs. *P <0.05.Back to article page