[Effect of capsaicin-pretreatment on "Sibai" (ST 2)-electroacupuncture induced changes of c-fos expression in rat caudal spinal trigeminal nucleus].
OBJECTIVE
To explore the afferent pathway of signals from electroacupuncture (EA) at "Sibai" (ST 2) acupoint.


METHODS
A total of 36 SD rats were randomly divided into control, sham operation (sham), capsaicin, vehicle, capsaicin + EA, and vehicle + EA groups, with 6 cases in each. EA (1/20 Hz, 1-3 mA) was applied to "Sibai" (ST 2). After anesthesia (10% urethane), unilateral infraorbital nerve was separated to be immersed in a 1.5% capsaicin-fluid-soaked cotton ball for lesion of C fibers. Vehicle (20% tween) was used to immerse infraorbital nerve for vehicle and vechile + EA groups. The expression of c-fos in the caudal spinal trigeminal nucleus (cSTN) was detected by immunohistochemistry.


RESULTS
In control group, c-fos immune-reaction (IR) positive neurons were observed to scatter in every layer of cSTN. No significant differences were found among vehicle, capsaicin, sham and control groups in the number of c-fos IR positive neurons in cSTN. The number of c-fos positive neurons in the I-II layers of cSTN was obviously increased following EA at ST2, being significant more than that in control, vehicle, capsaicin and sham groups (P<0.01 respectively). However, the number of c-fos IR-positive neurons in III-IV layers of cSTN had no marked change. In capsaicin + EA group, the number of c-fos-IR positive neurons in the I-II layers of cSTN was obviously less than that in vehicle and vehicle + EA groups (P<0.01), but no significant changes were found in III-IV layers of cSTN.


CONCLUSIONS
C afferent fibers of the infraorbital nerve are the primary afferent pathway of EA signals from Sibai (ST 2) stimulation in the rat.
Liu
Jian-hua
JH
Department of Acu-moxibustion, Guangdong Provincial Hospital of Chinese Medicine, Guangzhou 510120, China. ljh1008@21cn.com
Fu
Wen-bin
WB
Yan
Jie
J
D015669:Acupuncture Points; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D015671:Electroacupuncture; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics* / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014279:Trigeminal Nucleus, Spinal / Q000187:drug effects* / Q000378:metabolism*
D016760:Proto-Oncogene Proteins c-fos; D002211:Capsaicin