Effects of combination treatment with dexamethasone and mannitol on neuronal damage and survival in experimental heat stroke.

There is evidence that increased plasma cytokines, elevated brain levels of monoamines and hydroxyl radical production may be implicated in pathogenesis during heat stroke in rats. Acute treatment with a combined therapeutic approach has been repeatedly advocated in cerebral ischemia experiments. The aim of this study was to investigate whether the combined agent (mannitol and dexamethasone) has beneficial efficacy to improve the survival time (ST) and heat stroke-induced damage in experimental heat stroke. Urethane-anesthetized rats underwent instrumentation for the measurement of colonic temperature, mean arterial pressure (MAP), striatal cerebral blood flow (CBF), heart rate, and neuronal damage score. The rats were exposed to an ambient temperature (43 degrees C) to induce heat stroke. Concentrations of the ischemic and damage markers, dopamine, serotonin, and hydroxyl radical production in corpus striatum, and the plasma levels of tumor necrosis factor-alpha (TNF-alpha) were observed during heat stroke. After the onset of heat stroke, the heat stroke rats display decreased MAP, decreased CBF, increased the plasma levels of TNF-alpha, increased cerebral striatal monoamines and hydroxyl radical production release, and severe cerebral ischemia and neuronal damage compared with those of normothermic control rats. However, immediate treatment with the combined agent confers significant protection against heat stroke-induced arterial hypotension, systemic inflammation, cerebral ischemia, cerebral monoamines and hydroxyl radical production overloads, and improves neuronal damage and the ST in heat stroke rats. Our data suggest that administration of this combined agent seems to have more effective to ameliorate the heat stroke-induced neuronal damage and prolong the ST.