| Summary: | 碩士 === 國立政治大學 === 神經科學研究所 === 102 === The hippocampus is a brain region critical to learning and memory and is a frequent target of many neurological diseases such as Alzheimer’s, other forms of dementia, and chronic stress that have dramatic cognitive consequences. The Subgranular zone (SGZ) of the hippocampus is one of the mammalian brain regions where new neurons are generated continuously throughout adult life. Previously, we have successfully promoted adult neurogenesis and demonstrated functional recovery after hippocampal granule cell degeneration in a rat model.
This study was undertaken to address the question of whether the adult-born neurons were integrated into a neural network and involved in the process of learning and memory. Corticosterone, secreted by adrenal glands, is required for hippocampal granule cell survival and bilateral removal of adrenal glands lead to granule cell death. Therefore, adrenalectomized (ADX) rats were used to ablate, and regenerate granule cells in the hippocampus. Three months after treatment of ADX animals with sonic hedgehog (shh) and environmental enrichment, significant amount of granule cell regeneration and restoration of brain function was observed. To determine whether the new born neurons were integrated into a neural network and participated in the learning and memory process, immunohistochemistry for Arc, a synaptic activity dependent immediate early gene product was performed after behavior test. Colocalization of Arc and BrdU (a marker for neurons born 10 weeks ago) staining suggests that new neurons which were born during shh treatment were involved in the learning and memory. Colocalization of Arc and BrdU was more abundant in the dentate gyrus of the hippocampus in ADX animals treated with shh and housed in the enriched environment when compared with untreated ADX animals or ADX animals treated with shh but housed in cages. These results suggest that after treatment with shh and environmental enrichment, new born neurons survives for at least 3 months and participates in the activities of neural networks.
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