Inhibition of central angiotensin-converting enzyme with enalapril protects the brain from ischemia/reperfusion injury in normotensive rat

BACKGROUND AND THE PURPOSE OF THE STUDY Central Angiotensin Converting Enzyme (ACE) has an important role on cerebral microcirculation and metabolism. However, its role in terms of protecting the brain from ischemic/reperfusion (I/R) injury are debatable. This study evaluated the role of ACE, using enalapril as ACE inhibitor, in protection of the brain from I/R injury during transient focal cerebral ischemia (TFCI) in normotensive rat. METHOD Male Sprague Dawley rats (280-320g) randomly assigned to control ischemic and enalapril pre-treated ischemic groups. Enalapril was injected intraperitoneally 1 h before middle cerebral artery occlusion (MCAO) at the dose of 0.03 or 0.1 mg/kg. Cerebral ischemia was induced by 60 min MCAO followed by 24 hrs reperfusion. After evaluation of neurological deficit scores (NDS) the animal was sacrificed for assessment of cerebral infarction and edema. RESULTS TFCI induced cerebral infarctions (283±18 mm(3)), brain edema (4.1±0.4%) and swelling (9.8±1.5%) with NDS of 3.11±0.36. Non-hypotensive dose of enalapril (0.03 mg/kg) improved NDS (1.37±0.26), reduced cerebral infarction (45%), brain edema (54%) and swelling of the lesioned hemispheres (34%) significantly. However, hypotensive dose of enalapril (0.1 mg/kg) could improve neurological activity (1.67±0.31) and failed to reduce cerebral infarction (276±39 mm(3)) and swelling (10.4±1.4%). CONCLUSION In the rat model of transient focal cerebral ischemia, inhibition of angiotensin converting enzyme with non-hypotensive doses of enalapril has the benefit of improving neurological activity, reducing cerebral infarction, brain swelling and edema of acute ischemic stroke. Therefore, it is reasonable to conclude that central renin-angiotensin system may participate in ischemic/reperfusion injury of the cerebral cortex.