1.Orexin-A inhibits capsaicin-induced changes in cyclooxygenase-2 and brain-derived neurotrophic factor expression in trigeminal nucleus caudalis of rats
Razieh KOOSHKI ; Mehdi ABBASNEJAD ; Saeed ESMAEILI MAHANI ; Maryam RAOOF ; Mohammad Mehdi MOEINI AGHTAEI ; Shahriar DABIRI
The Korean Journal of Pain 2018;31(3):174-182
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.
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