Electroacupuncture activates corticotrophin-releasing hormone-containing neurons in the paraventricular nucleus of the hypothalammus to alleviate edema in a rat model of inflammation.

Abstract

BACKGROUND:

Studies show that electroacupuncture (EA) has beneficial effects in patients with inflammatory diseases. This study investigated the mechanisms of EA anti-inflammation, using a rat model of complete Freund's adjuvant (CFA)-induced hind paw inflammation and hyperalgesia.

DESIGN:

Four experiments were conducted on male Sprague-Dawley rats (n = 6-7/per group). Inflammation was induced by injecting CFA into the plantar surface of one hind paw. Experiment 1 examined whether EA increases plasma adrenocorticotropic hormone (ACTH) levels. Experiments 2 and 3 studied the effects of the ACTH and corticotropin-releasing hormone (CRH) receptor antagonists, ACTH(11-24) and astressin, on the EA anti-edema. Experiment 4 determined whether EA activates CRH neurons in the paraventricular nucleus of the hypothalammus. EA treatment, 10 Hz at 3 mA and 0.1 ms pulse width, was given twice for 20 min each, once immediately post and again 2 hr post-CFA. Plasma ACTH levels, paw thickness, and paw withdrawal latency to a noxious thermal stimulus were measured 2 h and 5 h after the CFA.

RESULTS:

EA significantly increased ACTH levels 5 h (2 folds) after CFA compared to sham EA control, but EA alone in naive rats and CFA alone did not induce significant increases in ACTH. ACTH(11-24) and astressin blocked EA anti-edema but not EA anti-hyperalgesia. EA induced phosphorylation of NR1, an essential subunit of the N-methyl-D-aspartic acid (NMDA) receptor, in CRH-containing neurons of the paraventricular nucleus.

CONCLUSION:

The data demonstrate that EA activates CRH neurons to significantly increase plasma ACTH levels and suppress edema through CRH and ACTH receptors in a rat model of inflammation.

• Authors: Aihui Li, Lixing Lao, Yi Wang, Jiajia Xin, Ke Ren, Brian M Berman, Ming Tan, Ruixin Zhang
• Journal: BMC complementary and alternative medicine (BMC Complement Altern Med) Vol. 8 Pg. 20 (May 12 2008) ISSN: 1472-6882 [Electronic] England
• PMID: 18474100 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Freund's Adjuvant
• Corticotropin-Releasing Hormone

Topics

• Analysis of Variance
• Animals
• Corticotropin-Releasing Hormone (metabolism)
• Disease Models, Animal
• Edema (etiology, metabolism, prevention & control)
• Electroacupuncture
• Freund's Adjuvant
• Hyperalgesia (drug therapy, etiology, metabolism)
• Inflammation (chemically induced, complications, metabolism, therapy)
• Male
• Paraventricular Hypothalamic Nucleus (metabolism)
• Random Allocation
• Rats
• Rats, Sprague-Dawley