The influence of the cannabinoid receptor CB1 on the periaqueductal gray in mice treated with photobiomodulation after chronic constriction injury of the sciatic nerve: a placebo-controlled trial

Abstract

BACKGROUND AND OBJECTIVES: Studies have demonstrated that the cannabinoid CB1 receptor is involved in the modulation of pain, mainly by activating the descending pain control pathway. However, the role of photobiomodulation in this process is not well elucidated. Thus, the present study aimed to investigate the involvement of the CB1 receptor in the supraspinal photobiomodulation-induced antinociception. METHODS: Male albino swiss mice were submitted to chronic constriction injury and treated with photobiomodulation. To evaluate the supraspinal involvement of the CB1 receptor in the photobiomodulation-induced antinociception, the cannabinoid CB1 receptor antagonist AM251 (0.1µg/vol 0.2µL) was injected 5 minutes before the photobiomodulation treatment. The photobiomodulation treatment was performed on the fifth day after the stereotactic surgery and chronic constriction injury at a dose of 50J/cm 2 in acute condition. The hot plate and von Frey monofilaments tests were performed to evaluate the thermal and mechanical pain sensitivity, respectively. RESULTS: The thermal and mechanical nociceptive threshold was higher in mice with chronic constriction injury, injected with saline and treated with photobiomodulation at the dose of The influence of the cannabinoid receptor CB1 on the periaqueductal gray in mice treated with photobiomodulation after chronic constriction injury of the sciatic nerve: a placebo-controlled trial Influência do receptor canabinóide CB1 na substância cinzenta periaquedutal em camundongos tratados por fotobiomodulação após constrição crônica do nervo ciático: ensaio controlado por placebo