Effects of Aging on the Volume of Hippocampal Subdivisions in Rat

The hippocampus is a well-defined region of the brain involved in memory. Recent MRI studies have shown that there is hippocampal atrophy in elderly. However, in human studies, the influence of age on hippocampal atrophy is confounded with other variables, such as inadequate nutrition, psychological and physical stress. Therefore, this study aimed to determine the effects of normal advanced aging on the volume of the hippocampal subdivisions using animal model of rat. Male Wistar rats were maintained under constant laboratory conditions until sacrifice at 6(young) and 24 (old) months of age. Coronal sections with a thickness of 25 μm were cut serially through the entire extent of the hippocampus. Using systematic uniformly random sampling, 10-12 sections were selected, mounted on slides and stained with Hematoxilin. The Cavalieri principle was used to estimate the volumes of the main subdivisions of hippocampus. Statistical analysis revealed a significant influence of age in the stratum radiatum and lacunosum-molecular area of the CA1 pyramidal field, wherein the volume was lower in aged than young rats (P<0.05). Results also showed an insignificant difference between the total volume of hippocampus of aged and young rats(P=0.74). The findings of this research reflect likely alterations in the neuritis of hippocampal cells, a hypothesis that should be examined with electromicroscopic and golgi studies. This data provides a neuroanatomical basis that may be relevant to the reported disturbances in behavior and memory in the aged.