Background: Methylene Blue (MB) can prevent electron leaking, increase mitochondrial oxidative phosphorylation, and reduce ROS overproduction under pathological conditions, currently being trace evidence that it can alter pain perception in humans by local administration during certain surgical procedures. Riboflavin or vitamin B2 (B2) constitutes a part of the vitamin B group, which in recent studies shows a growing implication in the treatment of some pathology that imply pain management.
Aim: To investigate the effect of one dose of Riboflavin and Methylene Blue on nociception and visceral pain in mice.
Methods: A total of 48 BALB/c male mice were divided into 3 groups: MB Group, B2 Group and C Group. MB (5 mg/kg b.w.), B2 (100 mg/kg b.w.) or an equivalent volume of saline was administered intraperitoneally. Mice were tested before (baseline) and after drugs administration over a 4h period. Nociception was evaluated by means of Hot Plate Test (HPT) and TFT (Tail Flick Test). Visceral pain was evaluated 2h after administration.
Results: Four hours after MB administration we recorded an analgesic effect on the hot plate test (p < 0.05 at 30, 60 and 240 min). No significant effect on the TFT was noticed. B2 vitamin had an antinociceptive effect as compared to control group only for HPT that persisted for 2h but had no effect on TFT. Both MB and B2 vitamin have shown an analgesic effect (p < 0.01) on visceral pain when compared to the control group but the pain inhibition was more important after riboflavin administration.
Conclusions: Even if the exact mechanisms are not clarified by our study, we demonstrated that both ATP modulators (MB & B2 vitamin) have analgesic effect on visceral pain and nociception.