Histopathological Assessments of Animal Models of Cerebral Ischemia - Animal Models of Acute Neurological Injuries: Injury and Mechanistic Assessments - page 9

8. Clear in citrus fruit oil.
9. Mount on slide using mounting medium.

The histopathological technique described above can be (1) rou-
tinely performed in a laboratory, (2) less expensive, and (3) repro-
ducible. The limitation is that this technique can be used only after
the animal is dead.

4. Outcome
Evaluation

4.1. Quantifi cation
of Neuronal Death

The number of dead neurons in defi ned brain regions after cerebral
ischemia can be quantifi ed. Quantifi cation is commonly done by
counting all the normal and dead neurons at the same anatomic
levels of neocortical, striatal, and hippocampal brain sections from
both sham-operated control and postischemic subjects under light
microscopy ( 5 ). The extent of injury is usually expressed as the
percent of dead neurons of the total neurons in the defi ned regions
examined. For statistical comparisons of neuronal death between
experimental groups, the Kruskal-Wallis test followed by the Mann-
Whitney U test is commonly used. Typically, in global cerebral
ischemia models, less than 5 min of transient ischemia leads to little
neuronal death in all brain regions. Ten minutes of ischemia induces
delayed neuronal death selectively in about 80% of CA1 pyramidal
neurons, and in a few neocortical neurons. Fifteen minutes of

Fig. 4. Typical healthy neurons in CA1 region of hippocampus ( a ). ( b ) Histological assessment in hippocampus 7 days after
cerebral ischemia. ( c , d ) Represent normal and ischemic neurons at higher magnifi cation (40× magnifi cation). Arrow ( → )
shows normal neurons in CA1 region of hippocampus. Arrow ( → ) shows neurons exhibiting ischemic cell changes in CA1
region of hippocampus.