title: Neonatal capsaicin treatment in rats induces chronic hyperthermia resulting in infectious disease.
abstract: Treatment of neonatal animals with capsaicin has previously been associated with long-lasting hyperthermia and severe cutaneous lesions. The present study analyzed the effects of capsaicin-induced hyperthermia on the occurrence of infectious disease and pruritic dermatitis in a rat model. Pregnant Sprague-Dawley (SD) rats were obtained 1 week prior to parturition. Pups from each litter were randomly assigned to the following experimental groups: Capsaicin-treated (cap-treated; n=10) or vehicle-treated (n=5). Capsaicin (50 mg/kg) or vehicle were systemically administered to the SD rat pups (age, 48 h), after which body temperature was measured using a biotelemetry system, and the effects of hyperthermia on the ability of the rat pups to resist bacterial infection were analyzed. Furthermore, pruritus-induced scratching behavior and dermatitis were assessed, and changes in interleukin (IL)-4- and IL-13-induced immunoglobulin E expression were measured. Treatment of neonatal rats with capsaicin resulted in chronic hyperthermia, which had negative effects on the host immune defense response. The expression levels of T-helper type 2 cell-associated cytokines were significantly increased (P<0.01) in the cap-treated rats following bacterial infection withStaphylococcus aureusorStreptococcus agalactiae. Furthermore, cap-treated rats exhibited pruritus-induced scratching behavior and dermatitis. The results of the present study suggested that treatment of neonatal rats with capsaicin induces chronic hyperthermia and decreases the effectiveness of the host defense system. Therefore, a cap-treated neonatal rat model may be considered useful when investigating the association between hyperthermia and infectious disease.
authors.affiliation: College of Pharmacy, Gachon Institute of Pharmaceutical Sciences, Gachon University, Incheon 406-840, Republic of Korea.
authors.forename: Keun-Yeong
authors.initials: KY
authors.lastname: Jeong
authors.affiliation: College of Pharmacy, Gachon Institute of Pharmaceutical Sciences, Gachon University, Incheon 406-840, Republic of Korea.
authors.forename: Hwan Mook
authors.initials: HM
authors.lastname: Kim
keywords: bacterial infection; hyperthermia; neonatal capsaicin treatment; pruritus; rat