Effect of 5-HT on pain modulation of substance P in spinal cord of rats.
OBJECTIVE
To study the effect of serotonin (5-HT) on pain modulation of substance P (SP) in spinal cord of rats.


METHODS
Using immunohisto-chemistry and measurement of pain threshold.


RESULTS
The c-fos expression evoked by intrathecal injection (it) SP 10 micrograms and sc 5% formaldehyde (For) 150 microL in the hindpaw was densely distributed in the laminae I, II, V, and VI of spinal dorsal horn. The pain threshold in the SP group was decreased while the pain intensity rating measured by behavioral method in the For group was increased. The c-fos expression induced by it 5-HT 20 micrograms was mostly distributed in the spinal dorsal horn in laminae III-IV and the pain threshold was increased. SP and For induced c-fos expressions in the spinal cord and the pain responses were reduced by 5-HT and increased by 5-HT depletor fenclonine 300 mg.kg-1.


CONCLUSIONS
SP mainly played an algogenesia in the spinal cord. 5-HT inhibited the c-fos expression in the spinal cord evoked by SP and participated in pain modulation of SP.
Ruan
H Z
HZ
Department of Physiology, Third Military Medical College, Chongqing, China.
Li
X C
XC
Cai
W Q
WQ
D000818:Animals; D005260:Female; D016762:Genes, fos; D008297:Male; D017288:Pain Threshold / Q000187:drug effects*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013116:Spinal Cord / Q000378:metabolism*; D013373:Substance P / Q000502:physiology*
D016760:Proto-Oncogene Proteins c-fos; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D013373:Substance P