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 Magnolia officinalis Rehd, et Wils, on thermoregulation and hypothalamic release of 5-hydroxytryptamine (5-HT) by in vivo microdialysis were assessed in normothermic rats and in febrile rats treated with interleukin-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 endogenous release of 5-HT in the rat hypothalamus, 3, Depletion of rat brain 5-HT, produced by intracerebroventricular pretreatment with 5,7-dihydroxytryptamine, attenuated the magnolol-induced hypothermia, cutaneous vasodilation and decreased metabolism, 4, Intracetebroventricular administration of (+/-)-2,5-dimethoxy-4-iodoamphetamine (a 5-HT2 receptor agonist; 5-10 mu g/5 mu L) increased basal colon temperature and reversed the magnolol-induced hypothermia. 5, The increases in both colon 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 heat loss and decreased heat production) by reducing 5-HT release in rat hypothalamus.