Clinical reports suggest that the hippocampus is a structure closely related to the functioning of memory and it plays a significant role in the learning process (15). It is also known that anoxia frequently induces degenerating alterations in the CNS whose characteristic features are lesion and cell necrosis. The alterations of this type appear in various fields and also in the hippocampus [2, 8, 9]. Sommer  was the first to report that this CNS area is very sensitive to damages during anoxia or epilepsy. Since there are different relations between the Willis' arterial circle and the system of vertebral and carotid arteries in different animals [4, 5], the effects of any vessel occlusion will vary.