Dopamine depletion protects striatal neurons from heatstroke-induced ischemia and cell death in rats

To explore the importance of brain dopamine in the heatstroke-induced striatal ischemia and neuronal injury, we compared the temporal profile of the heatstroke-induced striatal extracellular dopamine release, striatal blood flow, and striatal neuronal loss in rats with or without striatal dopamine depletion produced by 6-hydroxydopamine. In vivo voltammetry was used in rats to measure changes in extracellular concentrations of dopamine in the corpus striatum. Striatal neuronal damage was rated on a scale from zero to three (0, no damage; 3, maximum cell loss). The autoradiographic diffusible tracer technique was used for the measurement of striatal blood flow. After the onset of heatstroke, the heatstroke rats without brain dopamine depletion displayed hyperthermia, decreased mean arterial pressure, increased intracranial pressure, decreased cerebral perfusion pressure, decreased striatal blood flow, increased striatal dopamine release, and increased score of striatal neuronal damage as compared with those of normothermic controls. However, when the striatal dopamine system was destroyed by 6-hydroxydopamine, the heatstroke-induced arterial hypotension, intracranial hypertension, ischemic damage to the striatum, and elevated striatal dopamine release were reduced. In addition, the survival time of the heatstroke rats was prolonged after depleting striatal dopamine. Thus it appears that dopamine depletion protects striatal neurons from heatstroke-induced ischemia and cell death.