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Afferent C-fibres release substance P and glutamate
1Institute of Experimental Pharmacology, Slovak Academy of Sciences, Bratislava, Slovakia.
Canadian Journal of Physiology and Pharmacology
|June 1, 1997
Summary
Capsaicin triggers glutamate release from spinal cord C-fibers, involving substance P. This study clarifies capsaicin
Area of Science:
- Neuroscience
- Pharmacology
- Neurochemistry
Background:
- Capsaicin is a tool to study primary afferent C-fibers, crucial for neurogenic inflammation via substance P and calcitonin gene-related peptide.
- Central functions involve N-methyl-D-aspartate (NMDA) receptor activation.
- Understanding capsaicin's mechanism in the spinal cord is essential for pain and inflammation research.
Purpose of the Study:
- To investigate the mechanisms of capsaicin-induced glutamate release from rat spinal cord slices.
- To determine the role of substance P and NMDA receptors in capsaicin's effects.
- To analyze glutamate release patterns in dorsal and ventral horns of the spinal cord.
Main Methods:
- Utilized continuous monitoring of glutamate concentration in rat spinal cord slices.
- Administered capsaicin, substance P, NMDA antagonist MK-801, and tachykinin (NK-1) antagonist CP-99994.
- Compared glutamate release in capsaicin-desensitized rats and analyzed differences between dorsal and ventral horns.
Main Results:
- Both capsaicin and substance P induced concentration-dependent glutamate release from dorsal horns.
- The NK-1 antagonist CP-99994 significantly reduced responses to both capsaicin and substance P.
- Capsaicin-desensitized rats showed decreased, but not abolished, glutamate release, indicating partial C-fiber involvement.
Conclusions:
- Capsaicin primarily releases glutamate from afferent C-fibers in the spinal cord.
- Substance P facilitates capsaicin-induced glutamate release, as evidenced by the NK-1 antagonist's inhibitory effect.
- Glutamate release mechanisms in ventral horns are similar but quantitatively smaller than in dorsal horns.
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