Expression of Somatostatin, Preproenkaphalin, and Microtubule-associated Protein 1B Genes in the Rat Hippocampus after Inhibitory Avoidance Learning

• Main Author: 邱威喬
• Other Authors: 黃阿敏
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/83033750854952053899

碩士 === 國立成功大學 === 生理學研究所 === 89 === Studies have shown that cyclic AMP-responsive element binding protein (CREB)-dependent transcription is essential for long-term memory. However, the targets of CREB during long-term memory in the vertebrate remain largely unknown. CREB is a transcription factor that regulates the transcription of genes with cAMP responsive elements (CRE) (5’-TGACGTCA-3’) in their promoters. In this study, three potential cAMP responsive genes were tested for their expression during the process of memory formation, including somatostatin (SST), microtubule-associated protein 1B (MAP1B), and preproenkephalin (ppENK) genes. One-trial inhibitory avoidance learning task was used as the behavioral paradigm. Hippocampal total RNA was isolated from control rats and good memory rats that reach a ceiling score of 600 sec. The mRNA levels of these genes in the rat hippocampus at 0.5, 3, 6 and 24 hours after training were determined by the ribonuclease protection assay (RPA) and in situ hybridization. Results of RPA reveal that SST mRNA levels at 0.5, 6, and 24 hours after training are significant higher than those of the control group and at 24 hours after training ppENK mRNA has a significant increase as examined by independent t-test. No significant difference of MAP1B gene expression was found at these time points after training. The electric shock has no influence on the SST, MAP1B, and ppENK mRNA expression at 0.5 hour after training. In situ hybridization was used to determine the expression of these three genes within the subdivisions (ex. CA1, CA3 or DG) of the hippocampus. To confirm the specificity of antisense probes, sense probes was used as negative controls. SST mRNA was found to be significantly expressed in the hippocampal dentate gyrus and CA1 region 3, 6, and 24hr after training. No significant difference of MAP1B mRNA level was detected in the hippocampal subdivisions after training and ppENK mRNA signals were too weak to be detected. These findings suggest that these three genes are differentially regulated in terms of temporal and spatial patterns after inhibitory avoidance learning.