Antinociceptive Effects of Radon Inhalation on Formalin-Induced Inflammatory Pain in Mice

• Published in: Inflammation Vol. 36; no. 2; pp. 355 - 363
• Main Authors: Yamato, Keiko, Kataoka, Takahiro, Nishiyama, Yuichi, Taguchi, Takehito, Yamaoka, Kiyonori
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-04-2013; Springer Nature B.V
• Subjects: Administration, Inhalation; Air Pollutants, Radioactive - pharmacology; Analgesics - administration & dosage; Analgesics - pharmacology; Animals; Behavior, Animal - drug effects; Biomedical and Life Sciences; Biomedicine; Cell Movement - drug effects; Disease Models, Animal; Formaldehyde; Immunology; Inflammation - chemically induced; Inflammation - drug therapy; Internal Medicine; Leukocytes - metabolism; Male; Mice; Mice, Inbred ICR; Nitric Oxide - blood; Nociception - drug effects; Pain - chemically induced; Pain - drug therapy; Pain Measurement; Pathology; Pharmacology/Toxicology; Radon - administration & dosage; Radon - pharmacology; Rheumatology; Tumor Necrosis Factor-alpha - blood; nociception; inflammatory pain; antioxidants; radon inhalation; formalin test
• ISSN: 0360-3997; 1573-2576
• DOI: 10.1007/s10753-012-9554-2

Radon therapy is clinically useful for the treatment of inflammatory diseases. The mechanisms of pain relief remain to be fully elucidated. In this study, we investigated the antinociceptive effects of radon inhalation in a mouse model of formalin-induced inflammatory pain. Immediately, after radon inhalation at a concentration of background level (
ca
. 19 Bq/m
3
), 1,000 or 2,000 Bq/m
3
for 24 h, 1.35 % formalin (0.5 % formaldehyde in saline, 20 μl) was subcutaneously injected into the hind paw of mice, and we measured licking response time. Radon inhalation inhibited the second phase of response in formalin test. Formalin administration induced nociception and increased tumor necrosis factor alpha (TNF-α) and nitric oxide (NO) levels in serum and leukocyte migration in paws. Concurrently, formalin injection decreased antioxidative functions. Radon inhalation produced antinociceptive effects,
i
.
e
., lowered serum TNF-α and NO levels, and restored antioxidative functions. The results showed that radon inhalation inhibited formalin-induced inflammatory pain.