Involvement of spinal serotonin receptors in electroacupuncture anti-hyperalgesia in an inflammatory pain rat model.

Abstract

We previously showed that electroacupuncture (EA) activates medulla-spinal serotonin-containing neurons. The present study investigated the effects of intrathecal 5,7-dihydroxytryptamine creatinine sulfate, a selective neurotoxin for serotonergic terminals, the 5-hydroxytryptamine 1A receptor (5-HT1AR) antagonist NAN-190 hydrobromide and the 5-HT2C receptor (5-HT2CR) antagonist SB-242,084 on EA anti-hyperalgesia. EA was given twice at acupoint GB30 after complete Freund's adjuvant (CFA) injection into hind paw. CFA-induced hyperalgesia was measured by assessing hind paw withdrawal latency (PWL) to a noxious thermal stimulus 30 min post-EA. Serotonin depletion and the 5-HT1AR antagonist blocked EA anti-hyperalgesia; the 5-HT2CR antagonist did not. Immunohistochemical staining showed that spinal 5-HT1AR was expressed and that 5-HT2CR was absent in naive and CFA-injected animals 2.5 h post-CFA. These results show a correlation between EA anti-hyperalgesia and receptor expression. Collectively, the data show that EA activates supraspinal serotonin neurons to release 5-HT, which acts on spinal 5-HT1AR to inhibit hyperalgesia.

• Authors: Yu Zhang, Aihui Li, Jiajia Xin, Lixing Lao, Ke Ren, Brian M Berman, Ming Tan, Rui-Xin Zhang
• Journal: Neurochemical research (Neurochem Res) Vol. 36 Issue 10 Pg. 1785-92 (Oct 2011) ISSN: 1573-6903 [Electronic] United States
• PMID: 21556842 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• 6-chloro-5-methyl-1-((2-(2-methylpyrid-3-yloxy)pyrid-5-yl)carbamoyl)indoline
• Aminopyridines
• Indoles
• Piperazines
• Receptor, Serotonin, 5-HT2C
• Serotonin 5-HT1 Receptor Antagonists
• Receptor, Serotonin, 5-HT1A
• 1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine
• Serotonin
• 5,7-dihydroxytryptamine creatinine
• Creatinine
• 5,6-Dihydroxytryptamine

Topics

• 5,6-Dihydroxytryptamine (analogs & derivatives, pharmacology)
• Aminopyridines (pharmacology)
• Animals
• Behavior, Animal (drug effects)
• Creatinine (analogs & derivatives, pharmacology)
• Electroacupuncture (methods)
• Hyperalgesia (physiopathology, therapy)
• Indoles (pharmacology)
• Inflammation (physiopathology)
• Male
• Pain (physiopathology)
• Piperazines (pharmacology)
• Random Allocation
• Rats
• Rats, Sprague-Dawley
• Receptor, Serotonin, 5-HT1A (metabolism)
• Receptor, Serotonin, 5-HT2C (metabolism)
• Serotonergic Neurons (drug effects, metabolism)
• Serotonin (metabolism)
• Serotonin 5-HT1 Receptor Antagonists (pharmacology)
• Spinal Cord (cytology, metabolism)