Analgesic effects by electroacupuncture were decreased in inducible nitric oxide synthase knockout mice.
BACKGROUND
This study was designed to investigate the involvement of inducible nitric oxide synthase (iNOS) in electroacupuncture (EA)-induced analgesia.


METHODS
Two and 100 Hz EA stimulation were applied at acupoint ST 36 (Zusanli) in iNOS knockout mice (n = 28). Needles were inserted 5 mm in depth in ST36. After insertion, the needles were fixed in situ with adhesive tape. EA was applied after the basal threshold determination. The EA parameters were set as follows: constant square wave current output (pulse width: 0.6 ms at 2 Hz and 0.2 ms at 100 Hz) and 2 mA intensities. EA was performed for 30 minutes and tail-flick latencies (TFLs) were evaluated every 15 minutes for 1 hour.


RESULTS
In 2 Hz EA stimulation, the tail-flick response (TFR) of wild-type mice for durations of 0, 15, 30, 45 and 60 minutes were 2.70 +/- 0.26, 4.19 +/- 0.37, 4.17 +/- 0.34, 3.57 +/- 0.27 and 3.39 +/- 0.32 seconds of TFLs. Meanwhile, iNOS -/- mice showed 4.10 +/- 0.33, 4.77 +/- 0.24, 5.26 +/- 0.30, 4.48 +/- 0.33 and 5.00 +/- 0.41 seconds of TFLs. In 100 Hz EA stimulation, the TFR of wild-type mice were 3.01 +/- 0.24, 4.67 +/- 0.31, 4.76 +/- 0.25, 4.04 +/- 0.45 and 4.26 +/- 0.30 seconds of TFLs. The iNOS -/- mice were 4.33 +/- 0.16, 5.29 +/- 0.28, 5.06 +/- 0.35, 4.52 +/- 0.17 and 4.80 +/- 0.28 seconds of TFLs. Wild-type mice exhibited 63.9% increase in TFL compared to the baseline after 2 Hz EA, whereas the iNOS knockout mice exhibited 32.9% increase in TFL. The TFL after 100 Hz EA showed similar trends: 66.5% increase in TFL in wildtype mice and 18.3% increase in the iNOS knockout mice.


CONCLUSIONS
The present findings suggested that iNOS may play a crucial role in both low- and high-frequency EA-induced analgesic effects.
Kim
Ee-Hwa
EH
Department of Acupoint and Meridian, College of Korean Medicine, Semyung University, Jechon 390-711, Korea.
Park
Hi-Joon
HJ
Lee
Hyangsook
H
Seo
Jung-Chul
JC
Hong
Meesuk
M
Park
Hun-Kuk
HK
Jang
Mi-Hyeon
MH
Kim
Chang-Ju
CJ
Ha
Eunyoung
E
Lee
Hyejung
H
Kang
Sungkeel
S
Choi
Sunmi
S
Ryu
Yeonhee
Y
Chung
Joo-Ho
JH
D000698:Analgesia; D000818:Animals; D004307:Dose-Response Relationship, Radiation; D015671:Electroacupuncture / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency*; D017288:Pain Threshold / Q000502:physiology / Q000528:radiation effects*; D011930:Reaction Time / Q000528:radiation effects; D013997:Time Factors
D052247:Nitric Oxide Synthase Type II