Histopathological Assessments of Animal Models of Cerebral Ischemia

Histology is an essential technique to evaluate ischemic damage in the animal models. Histopathology often refers to the microscopic examination of pathological changes in the tissue. This chapter describes the procedure to prepare brain for histopathological evaluation. The basic steps for histological procedure includes perfusion of brain following desirable experimental condition, fixation of brain, paraffin embedding, cutting of brain sections, staining, and observation. In this chapter, we clearly define what precautions are to be taken while performing these steps. Regarding staining of brain sections to evaluate ischemic damage we describe hematoxylin and eosin Y method routinely used by various laboratories. Finally, we also present a monograph of histological outcome after global cerebral ischemia (10 min of 2-vessel occlusion and hypotension (2VO)) in a rat model. There are two chief histopathological changes in this 2VO ischemia model: (1) selective neuronal vulnerability; typically, CA1 pyramidal neurons of the hippocampus are most vulnerable, followed by dorsoventral striatal small-and medium-sized neurons, and pyramidal neurons in the layers 3–4 of the dorsolateral neocortex and (2) delayed neuronal damage, i.e., neuronal death does not occur immediately after transient ischemic episode, but takes place after 2–3 days of reperfusion. Using histology, we can identify characteristic neuronal loss in ischemic rat brain.