Sensitization of trigeminal nervous system by infraorbital nerve injury exacerbates the pathophysiology of migraine

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We established the chronic constriction injury of the infraorbital nerve (ION-CCI) rat model as a chronic orofacial pain model (neuropathic pain model) by ION loose ligation. At 3 weeks after ION-CCI, the dura was stimulated by 10mM capsaicin, which was the one of the migraine models, followed by checking the expression of the phosphorylated extracellular signal-regulated kinase (pERK) at the trigeminal spinal subnucleus caudalis by immunohistochemical staining method. It showed that the pERK-immunoreactive neurons statistically increased between ovex and 1440 μm caudally in ION-CCI + capisaisin stimulating group compared to capsaicin stimulating group. Taken together, the sensitization of 2nd branch of trigeminal nerve by ION-CCI affected the activation of 1stbranch of trigeminal nerve by capsaicin, suggesting that chronic orofacial pain may exacerbates the pathophysiology of migraine.