Abstract
Recent studies suggest the protective effects of adrenomedullin (AM) on ischemic brain damage. The present study was aimed at investigating the effects of AM and its receptor antagonist, AM 22–52, on ischemia-induced cerebral edema and brain swelling in rats using magnetic resonance imaging. Rats were subjected to 60 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. Intravenous injection of AM (1.0 μg/kg), AM 22–52 (1.0 μg/kg), or saline was made before MCAO. Effects of AM injection just after reperfusion were also investigated. One day after ischemia, increases in T 2-weighted signals in the brain were clearly observed. Total edema volume, as well as brain swelling, was greatly and significantly reduced by pre-treatment of AM (reduced by 53%). Extent of brain swelling was significantly correlated with the volume of cerebral edema. The protective effect of AM against edema was more clearly observed in the cerebral cortex (reduced by 63%) than the striatum (reduced by 31%). Increased T 2 relaxation time in the cortex was recovered partially by pre-treatment of AM. Post-treatment of AM had no effects. Pre-treatment of AM 22–52 tended to exacerbate the edema. In another line of experiment, cocktail administration of AM with melatonin, a pineal product having neuroprotective potential as a free radical scavenger, failed to enhance the protective effects of AM alone. The present study clearly suggests the prophylactic effects of AM against cerebral edema, especially the cortical edema, in a rat stroke model.
Published Version
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