Adrenomedullin reduces ischemic brain injury after transient middle cerebral artery occlusion in rats

Background The effect of adrenomedullin. a vasodilatory, peptide on transie nt middle cerebral artery (MCA) occlusion was investigated in rats. Methods. Transient MCA occlusion for 2 hours was made by using the intra-ar terial suture method, followed by reperfusion. Findings. An intravenous infusion of adrenomedullin (1 mug/kg/min) From one hour before ischemia to one hour after ischemia significantly reduced the infarct size and improved neurological deficits (p < 0.05). without affecti ng systemic blood pressure or other physiological parameters. The infarct s ize was reduced with adrenomedullin by 25.4 +/- 12.7% 31.3 +/- 5.8%, 31.6 /- 6.1% respectively at the coronal level 6, 9 and 10 min posterior from th e frontal pole. Adrenomedullin also significantly inhibited the increase in myeloperoxidase (MPO) activity in the MCA area of the ischemic hemisphere after 22-hour reperfusion (control: 0.205 +/- 0.054 unit/g wet tissue, adre nomedullin group: 0.047 +/- 0.009 unit/g wet tissue. p < 0.0001). Interpretation. These data suggest that adrenomedullin reduces acute ischem ic brain injury and one of is neuroprotective mechanisms may be derived fro m inhibition of the infiltration of neutrophils into the ischemic tissue.