Korean J Pain.  2018 Jul;31(3):174-182. 10.3344/kjp.2018.31.3.174.

Orexin-A inhibits capsaicin-induced changes in cyclooxygenase-2 and brain-derived neurotrophic factor expression in trigeminal nucleus caudalis of rats

Affiliations
  • 1Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Iran.
  • 2Endodontology Research Center, Kerman University of Medical Sciences, Kerman, Iran. Maryam.raoof@gmail.com
  • 3Laboratory of Molecular Neuroscience, Neuroscience Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.
  • 4Pathology and Stem Cell Research Center, Department of Pathology, Afzalipour Kerman University of Medical Science, Kerman, Iran.

Abstract

BACKGROUND
The trigeminal nucleus caudalis (Vc) is a primary central site for trigeminal transmitting. Noxious stimulation of the trigeminal nociceptors alters the central synaptic releases and neural expression of some inflammatory and trophic agents. Orexin-A and the orexin 1 receptor (OX1R) are expressed in pain pathways including trigeminal pain transmission. However, the the mechanism(s) underling orexin-A effects on trigeminal pain modulation have not been fully clarified.
METHODS
Trigeminal pain was induced by subcutaneous injection of capsaicin in the upper lip in rats. The effect of trigeminal pain on cyclooxygenase-2 (COX-2) and brain-derived neurotrophic factor (BDNF) expression in the Vc of animals was determined by immunofluorescence. Subsequently, OX1R agonist (orexin-A) and antagonist (SB-334867-A) was administrated in the Vc to investigate the possible roles of the Vc OX1R on changes in COX-2 and BDNF levels following pain induction.
RESULTS
The data indicated an increase in COX-2 and decrease in BDNF immuno-reactivity in the Vc of capsaicin, and capsaicin- pretreated with SB-334867-A (80 nM), groups of rat. However, the effect of capsaicin on COX-2 and BDNF expressions was reversed by a Vc microinjection of orexin-A (100 pM).
CONCLUSIONS
Overall, the present data reveals that orexin-A can attenuate capsaicin-induced trigeminal pain through the modulation of pain effects on COX-2 and BDNF expressions in the Vc of rats.

Keyword

Brain-derived neurotrophic factor (BDRF); Capsaicin; Cyclooxygenase 2 (COX 2); Orexin-A; Orexin receptor antagonists; Orofacial pain; Rats; Pain measurement; Pain perception; Trigeminal caudal nucleus; Trigeminal neuralgia

MeSH Terms

Animals
Brain-Derived Neurotrophic Factor*
Capsaicin
Cyclooxygenase 2*
Facial Pain
Fluorescent Antibody Technique
Injections, Subcutaneous
Lip
Microinjections
Nociceptors
Orexin Receptor Antagonists
Orexins*
Pain Measurement
Pain Perception
Rats*
Trigeminal Caudal Nucleus
Trigeminal Neuralgia
Trigeminal Nuclei*
Brain-Derived Neurotrophic Factor
Capsaicin
Cyclooxygenase 2
Orexin Receptor Antagonists
Orexins
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