Involvement of spinal orexin A in the electroacupuncture analgesia in a rat model of post-laparotomy pain
1 Department of Integrative Medicine and Neurobiology, Institute of Acupuncture Research, WHO Collaborating Center for Traditional Medicine, State Key Laboratory of Medical Neurobiology, Institutes of Brain Science, Shanghai Medical College, Fudan University, Shanghai, 20032, China
2 Shanghai Institute of Acupuncture-Moxibustion and Meridian, Shanghai, 200030, China
3 P.O. Box 291, 138 Yi Xue Yuan Road, Shanghai, 200032, China
BMC Complementary and Alternative Medicine 2012, 12:225 doi:10.1186/1472-6882-12-225Published: 22 November 2012
Orexin A (OXA, hypocretin/hcrt 1) is a newly discovered potential analgesic substance. However, whether OXA is involved in acupuncture analgesia remains unknown. The present study was designed to investigate the involvement of spinal OXA in electroacupuncture (EA) analgesia.
A modified rat model of post-laparotomy pain was adopted and evaluated. Von Frey filaments were used to measure mechanical allodynia of the hind paw and abdomen. EA at 2/15 Hz or 2/100 Hz was performed once on the bilateral ST36 and SP6 for 30 min perioperatively. SB-334867, a selective orexin 1 receptor (OX1R) antagonist with a higher affinity for OXA than OXB, was intrathecally injected to observe its effect on EA analgesia.
OXA at 0.3 nmol and EA at 2/15 Hz produced respective analgesic effects on the model (P<0.05). Pre-surgical intrathecal administered of SB-334867 30 nmol antagonized OXA analgesia and attenuated the analgesic effect of EA (P<0.05). However, SB-334867 did not block fentanyl-induced analgesia (P>0.05). In addition, naloxone, a selective opioid receptor antagonist, failed to antagonize OXA-induced analgesia (P>0.05).
The results of the present study indicate the involvement of OXA in EA analgesia via OX1R in an opioid-independent way.