Preventive and curative effects of radon inhalation on chronic constriction injury-induced neuropathic pain in mice

Abstract Background Radon therapy is clinically useful for the treatment of pain‐related diseases. However, there have been no studies regarding the effects of radon inhalation on neuropathic pain. In this study, we aimed to determine whether radon inhalation actually induced a remission of neuropathic pain and improved the quality of life. Methods First, we investigated the antinociceptive effects of radon inhalation in the chronic constriction injury ( CCI ) model of neuropathic pain. We evaluated pain behaviour in mice before and after CCI surgery, using von F rey test. Pretreated mice received CCI surgery immediately after 24‐h inhalation of radon at background ( BG ) concentration (c. 19 Bq/m 3 ), or at a concentration of 1000 or 2000 Bq/m 3 , and post‐treated mice inhaled similar levels of radon 2 days after CCI surgery. Results CCI surgery induced mechanical allodynia and hyperalgesia on a plantar surface of mice, as assessed using von F rey test, and 2000 Bq/m 3 radon inhalation alleviated hyperalgesic conditions 22–37% compared to BG level concentration. Concurrently, CCI surgery increased norepinephrine ( NE ), tumour necrosis factor‐alpha ( TNF ‐α) and nitric oxide ( NO ) concentrations in plasma, and leukocyte migration in paws. Furthermore, CCI ‐induced neuropathy reduced superoxide dismutase ( SOD ) activity. Treatment with radon inhalation, specifically at a concentration of 2000 Bq/m 3 , produced antinociceptive effects, i.e., lowered plasma TNF ‐α, NE and NO levels and restored SOD activity, as well as pain‐related behaviour. Conclusions This study showed that inhalation of 2000 Bq/m 3 radon prevented and alleviated CCI ‐induced neuropathic pain in mice.