Protective actions of dexamethasone in acute cerebral ischemia

The effects of glucocorticoids on cerebral integrity during cerebral ischemia (CI) are not clear. We induced CI in rabbits by occlusion of the left external carotid artery and injection of sodium arachidonate (NaAr) in the left internal carotid artery. We investigated the effect of dexamethasone (DEXA) on NaAr--induced CI. We examined four groups: a) Sham CI, b) CI, c) CI + Dopamine (80 micrograms/kg/min), and d) CI + Dopamine + DEXA (6 mg/kg). The EEG was recorded over the hemisphere injected with NaAr. After 240 min of observation, the brain was sampled to measure water content and to examine the cerebral vasculature microscopically. The dose of NaAr was similar in all ischemic groups (ie, 0.45 to 0.50 mg). In both CI, and CI + Dopamine groups, the EEG became flat in all 13 rabbits. Moreover, the water content of the left hemisphere increased (P less than 0.01 vs Sham CI), but that of the right side only slightly. In the CI + Dopamine + DEXA group, only one rabbit out of seven showed a flat EEG. Water content of the left side increased slightly and that of the right side not at all. Microscopic examination of the brain showed obstruction of cerebral arterioles in the left hemisphere in rabbits given NaAr. Thus, DEXA protects the brain from edema induced by NaAr, when blood pressure is maintained by dopamine. This is associated with preservation of cerebral electrical activity. However, dopamine alone was unable to preserve the EEG or protect against edema formation during cerebral ischemia.