Unchanged c-Fos expression after extracorporeal shock wave therapy: an experimental investigation in rats

Background: Despite the extensive use of extracorporeal shock wave therapy (ESWT) in the therapy of chronic tendopathies, the biological mechanisms of its antinociceptive effects are still unclear. Methods: In this study we addressed the question of whether the clinically described, long-lasting effect of ESWT is mediated by changes in the activity of spinal cord neurones. As a marker for neuronal activity which is also able to interfere with the molecular expression pattern of neurones, the expression of the inducible transcription factor c-Fos was analysed in the animal model of the rat. Despite application of different energy levels, the analysis of c-Fos protein expression at an early (4 h) and late (72 h) time point after ESWT revealed no visible changes in immunoreactivity in the dorsal horn of the spinal cord. Additionally, there was no change in c-Fos protein and its gene expression c-Fos mRNA in the treatment area of the paw. Results and conclusion: We conclude that ESWT with an energy flux dose up to 0.33 mJ/mm(2) does not modify neuronal activity. Since the application of ESWT showed no significant changes in the immunoreactivity of c-Fos, it is therefore unlikely that ESWT triggers stimulation-produced analgesia via activation of peripheral nerves.