Involvement of spinal orexin A in the electroacupuncture analgesia in a rat model of post-laparotomy pain

Abstract

BackgroundOrexin 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.MethodsA 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.ResultsOXA 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).ConclusionsThe results of the present study indicate the involvement of OXA in EA analgesia via OX1R in an opioid-independent way.

Changes in Biochemical Markers of Pain Perception and Stress Response After Spinal Manipulation

“…A recent study using a rat model reported a significant increase of orexin A following electroacupuncture therapy after a laparotomy. 25 In contrast, our results did not show a statistically significant change in orexin A levels after a thoracic or cervical SM.…”

Obesity and Headache: Part II – Potential Mechanism and Treatment Considerations

“…23 Animal and human data also support a role for orexins in pain processing. 20 In rat pain models, intrathecally administered OXA has anti-hyperalgesic properties, [24][25][26][27][28] and the specificity of OXA's anti-hyperalgesic effect has been demonstrated by its inhibition when pretreated with the orexin receptor antagonist. 25,29 Additionally, in humans, OXA levels have been shown to be elevated in the cerebrospinal fluid of chronic daily headache sufferers.…”

“…20 In rat pain models, intrathecally administered OXA has anti-hyperalgesic properties, [24][25][26][27][28] and the specificity of OXA's anti-hyperalgesic effect has been demonstrated by its inhibition when pretreated with the orexin receptor antagonist. 25,29 Additionally, in humans, OXA levels have been shown to be elevated in the cerebrospinal fluid of chronic daily headache sufferers. 30 The findings of OXA's antihyperalgesic properties in animal models and the elevated OXA levels in those with chronic daily headache may suggest orexin resistance or disruptions in orexin receptors in those with chronic headache (which explains the continued pain while having elevated OXA levels).…”

A pivotal role for enhanced brainstem Orexin receptor 1 signaling in the central cannabinoid receptor 1-mediated pressor response in conscious rats

“…RVLM orexin-A level was quantified with a standard ELISA kit (EK-003–30; Phoenix Pharmaceutical, Burlingame, CA) in accordance with the manufacturer’s procedures and as reported (Feng et al, 2007, 2012; Olszanecka-Glinianowicz et al, 2007). Briefly, four groups of animals treated as described under experimental design were euthanized 10–15 min after WIN55,212-2 or vehicle injection; brains were removed, flash frozen in 2-methylbutane (cooled on dry ice for at least 30 min), and stored at −80 °C until use.…”