Background and Aims
Intervertebral disc degeneration is associated with multiple stresses such as hypoxia and acidosis which are hypothesized to cause chronic pain, but how these stresses influence peripheral neuronal structures remains unknown.
Methods
The dorsal root ganglia (DRG) derived cell line ND7/23 was cultured under different oxygen tensions (2% and 20%) and pHs (6.8 and 7.4) for 3 days. Calcium imaging was performed at the end of culture to study nociception using bradykinin as stimulus and Fluo-4 as indicator. The longest neurite outgrowth per cell was quantified in calcein AM stained cells using ImageJ. SPSS was used for statistical analysis and p<0.05 was considered significant.
Results
Hypoxia but not low pH significantly increased proportion of cells with outgrowth and outgrowth length. Both low pH and hypoxia contributed to a higher proportion of cells with spontaneous and bradykinin-stimulated calcium response. The spontaneous and bradykinin-stimulated calcium increase speed and peak height were higher after pre-treatment of low pH and hypoxia.
Conclusions
While hypoxia promoted sprouting of neurite outgrowth, both acidosis and hypoxia are involved in spontaneous firing and inflammatory sensitization of DRG neurons.

EFFECT OF PH AND OXYGEN TENSION ON DORSAL ROOT GANGLION CALCIUM RESPONSE TO BRADYKININ AND NEURITE SPROUTING