[Effect of different frequency electroacupuncture on the expression of substance P and beta-endorphin in the hypothalamus in rats with gastric distension-induced pain].
OBJECTIVE
To observe the effect of different frequency electroacupuncture (EA) on hippocampal substance P (SP) and beta-endorphin (beta-EP) in rats with gastralgia so as to explore its underlying mechanism in preventing and relieving visceral pain.


METHODS
Fifty rats were randomly divided into control, sham operation, model, low- frequency-EA and high frequency-EA groups. Gastralgia model was duplicated by gastric distension (a pressure of 40 mmHg) with a latex balloon. Low (2 Hz) and high (100 Hz) frequency EA was applied to bilateral "Zusanli (ST 36)" for 30 min. Pain score was given by using Al-Chaer's method (abdominal withdrawal reflex) and the expression of hypothalamic beta-EP and SP was detected by immunohistochemistry.


RESULTS
Both low- and high-frequency EA of ST 36 could significantly lower the pain score (P < 0.01), and the effect of high-frequency EA was markedly superior to that of low-frequency (P < 0.01). Compared with control and sham-operation groups, both SP immuno-reaction (IR) and beta-EP IR positive cells in the hypothalamus in model group increased significantly in the number (P < 0.01), suggesting an upregulation of SP and beta-EP expression after occurrence of gastralgia. In comparison with model group, the number of SP IR and (beta-EP IR positive cells in the hypothalamus in low frequency and high frequency EA groups increased further (P < 0.01) particularly in low frequency EA group.


CONCLUSIONS
Both low-frequency and high-frequency EA of "Zusanli (ST 36)" can effectively relieve gastric distension-induced gastralgia in the rat, and the effect of high-frequency EA is better, which may be closely related to its actions in promoting the release and synthesis of hypothalamic beta-EP and SP.
Lin
Ya-Ping
YP
Keyr Laboratory of Meridian-Visceral Correlation Research, College of Acu-moxibustion and Massage, Hunan University of Chinese Medicine, Changsha 410007, China.
Peng
Yan
Y
Yi
Shou-Xiang
SX
Tang
Sen
S
D015746:Abdominal Pain / Q000209:etiology / Q000378:metabolism* / Q000628:therapy*; D015669:Acupuncture Points; D000818:Animals; D015671:Electroacupuncture / Q000379:methods*; D005786:Gene Expression Regulation; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D051381:Rats; D013373:Substance P / Q000378:metabolism*; D001615:beta-Endorphin / Q000378:metabolism*
D013373:Substance P; D001615:beta-Endorphin