Investigation of the effect of transcranial low-level laser therapy on pain threshold and light aversive behaviors and expression of PACAP, TRPA1, and IL-1β proteins in the trigeminal nucleus in a mice model of nitroglycerin-induced migraine

Abstract

Migraine is a debilitating headache that is caused by the inflammation of nerves and blood vessels, and usually is accompanied by various symptoms, including one-sided throbbing headache, nausea or vomiting, increased sensitivity to light (photophobia) and sound (phonophobia). Previous studies have shown the beneficial effects of low-power laser therapy in reducing pain in a variety of pain models. In this study, the effect of transcranial low power laser therapy (LLLT) on sensory sensitivity and photophobia behavior in an experimental model of migraine induced with nitroglycerin was investigated. Methods: 60 adult male mice divided into 5 groups of 12 including: Sham group, migraine group (NTG), NTG group and sumatriptan (600 µg/kg) recipient (NTG +SUMA), NTG group and transcranial LLLT at a wavelength of 808 nm (NTG+LLLT), and the NTG group and the combined recipient of laser and sumatriptan (NTG+LLLT+SUMA). Different groups received their corresponding treatment for five days. In the migraine group, nitroglycerin was injected at a dose of 5 mg/kg on days 1, 3, and 5, and two hours after the injection, to check the mechanical sensitivity of the hindpaw and the face and the thermal sensitivity of the paws, von Frey filaments and hot plate were performed, respectively. In addition, the light aversion behavior was checked by the light/dark box on the fifth day of the experiment. At the end, the animals were anesthetized by injecting ketamine and xylazine, and the trigeminal nucleus caudalis (TNC) was removed to investigate the protein expression of PACAP, TRPA1 and IL-1β by western blotting. Results: Treatment with LLLT and sumatriptan, alone or in combination, effectively reduced mechanical and thermal hyperalgesia caused by nitroglycerin. Also, treatment with LLLT and sumatriptan, alone or in combination, were able to reduce photophobia in nitroglycerin-received animals. These results were associated with a significant decrease in the expression of PACAP, TRPA1 and IL-1β proteins in the dorsal trigeminal nucleus.