Abstract
Radom therapy is clinically used for intervention of rheumatoid arthritis. The mechanism for the reduction of pain has not been clarified. In the present study, we investigated the relieving effect of radon inhalation on inflammatory pain. ICR mice (male and female, age: 8-9 weeks) inhaled radon at a concentration of 1000 Bq/m3 or 2000 Bq/m3 for 24 hours. Twenty μl of 0.5 % formaldehyde was injected into the hindpaw of the mice immediately after radon inhalation. Formalin injection induces a transient biphasic inflammatory pain. We examined the licking response time induced by formalin. In results, the first phase began immediately after formalin injection and lasted for 5 minutes. The second began 10 minutes after formalin injection and lasted for 20 minutes. Radon inhalation at a concentration of 1000 Bq/m3 or 2000 Bq/m3 did not inhibit the first phase of pain, suggesting that radon inhalation did not show the effects of narcotic analgesics such as morphine. However, radon inhalation at a concentration of 2000 Bq/m3 inhibited the second phase of pain, suggesting that radon inhalation show the effects of analgesic effects like nonsteroidal anti-inflammatory drugs (NSAIDs). We also found the migration of inflammatory leucocytes by formalin injection. However, radon inhalation inhibited the migration of inflammatory leucocytes. This report will be mentioned other changes in the characteristic of pathological observations, antioxidant function, or inflammatory mediators.
