A new model of transient focal cerebral ischemia for inducing selective neuronal necrosis.

Brief cerebral ischemia leads to selective neuronal necrosis (SNN), which is characterized by neuronal death with sparing of glial and vascular elements of the central nervous system. Understanding the pathophysiology of SNN may help elucidating the mechanisms and consequences of neuronal injury in humans following brief ischemia. Contrary to the presence of reproducible models of transient global ischemia, animal models of transient focal ischemia producing SNN are scarce and have important limitations such as causing ischemia in a vast area and inducing additional insults. In this study, we developed a practical mouse model of SNN without these limitations, by compressing the distal middle cerebral artery (MCA) with a blunted micropipette for 15 min. The success of compression was evaluated by monitoring the regional cerebral blood flow, and conventional histopathology and immunolabeling of the brain sections. Seven/fourteen days after ischemia, intracisternally administered propidium iodide labeled numerous necrotic cells in the frontoparietal cortex, which were mostly NeuN-positive, but were not immunolabeled with astrocytic markers (GFAP and S100), and showed neuronal morphology with hematoxylin-eosin staining, indicating that the model successfully induced ischemic injury limited to neurons. The model could become an important tool for investigating the long-term effects of brief ischemic events like transient ischemic attacks and could offer convenient reversible distal MCA occlusion for studies using intravital microscopy.