Immunocytochemical Study on the Changes of Cell-Death Controlling Factors in the Hippocampal Formation and Entorhinal Cortex of Aged Rats

Shin, Su Jin; Woo, Haing Won

Abstract

OBJECTIVES
Hippocampal formation and entorhinal cortex play a part in learning and memory. This study sought to investigate the change of cell-death controlling factors in the hippocampal formation and entorhinal cortex of aged rats.
METHODS
Ten aged rats and ten controls were studied. We performed immunocytochemical method using antibodies against NOS, VIP, c-fos , bcl-2, bax and p53 and in situ hybridization.
RESULTS
1) The number of nNOS-immunoreactive(IR) neurons in the entorhinal cortex was significantly decreased in the aged rats(>30%). Morphologically, the number of dendritic branches seemed to be decreased and the length of dendrites showed a tendency to by shortened in the aged group. A major loss of nNOS mRNA positive neurons was observed in the hippocampal formation of the aged rats(>30%). 2) VIP-IR neurons were predominantly bipolar cell. VIP-IR cells were mildly decreased in the hippocampus and subiculum(<15%), and moderately decreased in the dentate gyrus and entorhinal cortex of the aged rats(15-30%). The number and length of dendritic branches also appeared to have decreased and shortened in the aged group. 3) c-Fos immunoreactivity at cellular level was restricted only to the nucleus. c-Fos-IR nuclei were moderately decreased in the hippocampus(15-30%), and severely decreased in dentate gyrus, subiculum and entorhinal cortex of the aged rats(>30%). 4) Bcl-2 mRNA positive neurons were moderately decreased in the hippocampus, subiculum and entorhinal cortex(15-30%), and severely decreased in dentate gyrus of the aged rats(>30%). 5) Bax-IR neurons were similarly distributed between the control and the aged rats, but bax-IR neurons of the aged group, as compared to the control group, were weakly immunostained. 6) P53-IR neurons were only observed in hippocampal CA1 region of the aged rats.
CONCLUSION
These results indicate the involvement of neuronal system containing NOS, VIP, c-fos, bcl-2 and p53 in the brain aging process, and provide the morphological evidence for the changes in immunoreactivity of cell-death controlling factors in the hippocampal formation and entorhinal cortex of aged rats.