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Spinal pathways mediating coeruleospinal antinociception in the rat
Masayoshi Tsuruoka1, Masako Maeda, Ikuko Nagasawa
1Department of Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan. masa@dent.showa-u.ac.jp
Neuroscience Letters
|May 26, 2004
Summary
Descending axons from the locus coeruleus/subcoeruleus (LC/SC) that modulate pain signals travel through the ventrolateral spinal cord. Transecting this pathway blocks the pain-inhibiting effects of LC/SC stimulation.
Area of Science:
- Neuroscience
- Spinal Cord Research
- Pain Modulation
Background:
- Previous studies indicated that some locus coeruleus/subcoeruleus (LC/SC) neurons modulate nociception via descending spinal pathways.
- These pathways involve axons that descend ipsilaterally and cross the midline at specific spinal levels.
Purpose of the Study:
- To investigate the specific spinal pathway utilized by descending axons from the LC/SC involved in pain modulation.
- To determine whether the dorsolateral or ventrolateral funiculus is crucial for LC/SC-mediated descending inhibition.
Main Methods:
- Extracellular recordings were performed on dorsal horn neurons in rats.
- Spinal cord hemisection at the C2 level was used to isolate descending pathways.
- Dorsolateral and ventrolateral funiculi were selectively transected contralaterally to assess their role in LC/SC stimulation-induced inhibition of nociception.
Main Results:
- Stimulation of the LC/SC inhibited responses of dorsal horn neurons to noxious heat.
- Transection of the dorsolateral funiculus did not abolish this inhibition.
- Transection of the ventrolateral funiculus (VLF) abolished the inhibitory effect of LC/SC stimulation.
Conclusions:
- The findings strongly suggest that descending axons from the LC/SC that inhibit nociception descend within the ventrolateral quadrant of the spinal cord.
- The dorsolateral funiculus is not the primary pathway for this descending pain modulation from the LC/SC.