演題番号 : P1-m11
小沢 貴明 / Takaaki Ozawa:1 山田 一夫 / Kazuo Yamada:1 一谷 幸男 / Yukio Ichitani:1
1:筑波大院・行動神経科学 / Dept of Behav Neuro, Univ of Tsukuba,Ibaraki
We examined the roles of intra-hippocampal de novo mRNA and protein synthesis in each process of long-term spatial working memory including encoding, consolidation, retention and retrieval using delay-interposed radial arm maze task (dRAM). In experiment 1, male rats were trained to perform accurately on 8-arm radial arm maze task (RAM) in which a delay of 6 h was interposed after the fourth correct choice, then we tested the effects of intra-hippocampal administration of 5,6-dichloro-1-β-ribofuranosylbenzimidazole (DRB), a mRNA synthesis inhibitor, in various timings within a trial. DRB before the second-half of the trial impaired the subsequent performance, while that before the first-half did not, suggesting that hippocampal de novo mRNA synthesis is required for the retrieval process, but not for encoding/consolidation processes. In experiment 2, we tested the effects of intra-hippocampal emetine (EME), a protein synthesis inhibitor, in the dRAM using the rats tested in experiment 1. In contrast to DRB, EME before the first-half and that before the second-half impaired the second-half performance suggesting that hippocampal de novo protein synthesis is required both for encoding/consolidation and retrieval processes in dRAM. However, EME before the trial did not impair the non-delayed RAM performance, which requires only encoding and short-term maintenance of spatial information. Therefore, de novo protein synthesis is suggested to be important for consolidation rather than encoding process. Further, EME immediately after the first-half did not impair the second-half performance. This suggests that de novo protein synthesis-dependent consolidation process may finish rapidly after the first-half performance. In conclusion, these results suggest that (1) rapid memory consolidation in dRAM depends on hippocampal de novo protein synthesis, but not on mRNA synthesis, and (2) memory retrieval in dRAM requires hippocampal de novo mRNA and protein synthesis.