Memory-related gene expression in the rat hippocampus by the learning

Objectives: It has been reported that spatial learning and memory was impaired by loss of teeth, but the effect of teeth loss on the changes in gene expression was not clarified yet. In order to identify the memory-related gene expression by behavioral test, we performed DNA microarray analysis to investigate the changes in gene expression in the hippocampus.

Methods: Ten male Wistar rats were divided into two groups; the control group (n=5) and the maze experimental group (n=5). The maze experimental groups of rats performed the eight-arm radial maze one time per day since 7 weeks of age for 14 consecutive days, and number of the errors was counted. An error was defined as a re-entry into an arm that has already been visited. Total RNA was extracted from the hippocampus and subjected to microarray analysis (maze experimental vs. control). Validation analysis was performed with real-time quantitative PCR.

Results: The number of errors in the maze experimental group showed a gradual decrease depending on the progress of the maze task. Changes in expression with maze task occurred in 789 genes: up-regulation in 96 genes and down-regulation in 208 genes. We picked up 12 candidate genes in conjunction with the memory. Validation analysis was similar to the results of the microarray and the expression of Trh and Tnxa increased to about 4 and 3 times, respectively. In addition, the expression of S100a9 and Nnat decreased to about half both.

Conclusions: These results suggest that the eight-arm radial maze is involved in the induction of Trh, Tnxa, S100a9 and Nnat in hippocampus in rats.