MAGNOLOL DECREASES BODY-TEMPERATURE BY REDUCING 5-HYDROXYTRYPTAMINE RELEASE IN THE RAT HYPOTHALAMUS

1, The effects of magnolol, isolated and purified from the cortex of M agnolia officinalis Rehd, et Wils, on thermoregulation and hypothalami c release of 5-hydroxytryptamine (5-HT) by in vivo microdialysis were assessed in normothermic rats and in febrile rats treated with interle ukin-1 beta. 2, Intraperitoneal administration of magnolol (25-100 mg/ kg) produced a decrease in colon temperature, an increase in foot skin temperature, a decrease in metabolic rate and a decrease in the endog enous release of 5-HT in the rat hypothalamus, 3, Depletion of rat bra in 5-HT, produced by intracerebroventricular pretreatment with 5,7-dih ydroxytryptamine, attenuated the magnolol-induced hypothermia, cutaneo us vasodilation and decreased metabolism, 4, Intracetebroventricular a dministration of (+/-)-2,5-dimethoxy-4-iodoamphetamine (a 5-HT2 recept or agonist; 5-10 mu g/5 mu L) increased basal colon temperature and re versed the magnolol-induced hypothermia. 5, The increases in both colo n temperature and hypothalamic 5-HT release produced by interleukin-1 beta injection were attenuated by treatment with magnolol, 6, The data suggest that magnolol decreases body temperature (due to increased he at loss and decreased heat production) by reducing 5-HT release in rat hypothalamus.