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Sympathetic afferent units from lumbar intervertebral discs.
T Takebayashi1, J M Cavanaugh, S Kallakuri
1Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, Chuo-ku, Sapporo 060-8543, Japan. takebaya@sapmed.ac.jp
The Journal of Bone and Joint Surgery. British Volume
|March 29, 2006
Summary
Inflammation, not mechanical force alone, appears to sensitize lumbar discs, leading to discogenic low back pain. This neurophysiological study in rats suggests inflammation is key to mechanical sensitivity in spinal discs.
Area of Science:
- Neuroscience
- Pain Research
- Spinal Cord Anatomy
Background:
- Discogenic low back pain is a significant clinical challenge.
- The precise mechanisms underlying discogenic pain are not fully understood.
- Sympathetic nervous system involvement in spinal pain is an area of ongoing investigation.
Purpose of the Study:
- To investigate the neurophysiological basis of sympathetic afferent discharge from lumbar intervertebral discs.
- To explore the role of mechanical and inflammatory stimuli in activating these pathways.
- To elucidate the contribution of lumbar sympathetic pathways to discogenic low back pain.
Main Methods:
- Neurophysiological recordings from L2 root sympathetic afferent units in Lewis rats.
- Mechanical probing of L5-L6 intervertebral discs.
- Electrical stimulation of discs to evoke action potentials.
- Chemical induction of inflammation in the discs.
Main Results:
- No response to mechanical stimulation alone from L5-L6 discs.
- Electrical stimulation identified 42 sympathetic afferent units, primarily A-delta fibers.
- Inflammatory changes in discs led to sensitivity to mechanical probing.
- Nociceptive information transmission via the lumbar sympathetic trunk was observed post-inflammation.
Conclusions:
- Mechanical stimulation of lumbar discs may not inherently cause pain.
- Inflammatory processes appear crucial in sensitizing discs to mechanical stimuli.
- This pathway may contribute to discogenic low back pain by transmitting nociceptive signals.
- Findings may explain symptom variability in human degenerative disc disease.