Involvement of capsaicin-sensitive fibers in spinal NMDA-induced glutamate release.
The activation of spinal NMDA receptors can evoke glutamate release through the production of nitric oxide (NO) within the spinal cord, resulting in pain-relating behavior. In this study, we investigated the involvement of capsaicin-sensitive primary afferents in this phenomenon using in vivo intrathecal microdialysis. Intrathecal NMDA perfusion evoked increases in the concentrations of NO metabolises and glutamate and in pain-related behavior in both neonatal capsaicin and vehicle-treated rats. Although the degrees of increase in NO metabolises in capsaicin- and vehicle-treated rats were not significantly different, capsaicin-treated rats showed significantly smaller increases in glutamate concentration and pain-related behavior than did vehicle-treated rats. Our results showed that glutamate release from capsaicin-sensitive primary afferent terminals is involved in spinal NMDA-induced pain.
Kawamata
T
T
Department of Anesthesiology, Sapporo Medical University School of Medicine, South 1, West 16, Chuo-ku, Sapporo, Hokkaido 060-8543, Japan.
Omote
K
K
Toriyabe
M
M
Kawamata
M
M
Namiki
A
A
D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000494:pharmacology*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology*; D018698:Glutamic Acid / Q000096:biosynthesis / Q000378:metabolism*; D007278:Injections, Spinal; D008159:Lumbar Vertebrae; D008297:Male; D016202:N-Methylaspartate / Q000008:administration & dosage*; D009412:Nerve Fibers / Q000187:drug effects* / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D010146:Pain / Q000139:chemically induced / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism*
D018690:Excitatory Amino Acid Agonists; D009569:Nitric Oxide; D018698:Glutamic Acid; D016202:N-Methylaspartate; D002211:Capsaicin