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Does norepinephrine influence pain behavior mediated by dorsal root ganglia?: a pilot study
Katsumasa Tanimoto1, Tsuneo Takebayashi, Takeshi Kobayashi
1Department of Orthopaedic Surgery, Sapporo Medical University School of Medicine, South 1, West 16, Chuo-ku, Sapporo 060-8543, Japan. tanimoto@sapmed.ac.jp
Clinical Orthopaedics and Related Research
|February 12, 2011
Summary
Norepinephrine (NE) contributes to lumbar radicular pain by increasing dorsal root ganglion (DRG) neuron excitability, primarily through alpha-2 adrenoceptors. An alpha-2 antagonist may offer a new treatment strategy.
Area of Science:
- Neuroscience
- Pain Research
- Pharmacology
Background:
- Sympathetic nervous system postganglionic neurons and norepinephrine (NE) are implicated in lumbar radicular pain.
- Increased sympathetic nerve fibers in dorsal root ganglion (DRG) neurons have been observed in a root constriction model, but its validity for pain is uncertain.
Purpose of the Study:
- To determine if a root constriction model exhibits painful behaviors.
- To investigate if NE enhances DRG neuron excitability in this model.
- To identify the specific adrenoceptors mediating NE's effects on DRG neurons.
Main Methods:
- A lumbar root constriction model was created by suturing the L5 root.
- Behavioral tests were conducted up to 28 days post-surgery.
- Whole-cell patch clamp electrophysiology was used to record action potentials from DRG neurons treated with NE and adrenergic antagonists.
Main Results:
- Rats with root constriction displayed painful behaviors.
- NE significantly increased the excitability of DRG neurons in the constriction model.
- The effects of NE were blocked by alpha-antagonists and specifically by an alpha(2)-antagonist, but not an alpha(1)-antagonist.
Conclusions:
- NE plays a key role in generating lumbar radicular pain, predominantly through alpha(2)-adrenoceptors.
- Alpha(2)-antagonists show potential as a therapeutic agent for treating lumbar radicular pain.
