【进展】【Nature】胰岛素样生长因子II在记忆巩固与增强...

【进展】【Nature】胰岛素样生长因子II在记忆巩固与增强中发挥了重要作用

Figure 1A:Northern blot analysis showed that, compared to controls that were exposed to the box without foot shock and either euthanized immediately after (0 h2) or at paired time points (no shock, 2), the hippocampal expression of IGF-II mRNA did not change at 6 and 9 h but increased significantly at 20 h and had a strong trend towards an increase at 36 h after training
Figure 1B:Quantitative PCR with reverse transcription (qRT–PCR) analyses of mRNA extracts confirmed the significant increase of IGF-II mRNA 20 h after training compared to no-shock and 0 h2 controls whereas, in the same
extracts, IGF-I mRNA remained unchanged

Figure 1C:showed that hippocampal levels of IGF-II protein significantly increased at 20, but not at 72 or 96 h after training, compared to both time-matched unpaired and 0 h2 controls
结论：IA training leads to an increase in IGF-II that temporally overlaps that of C/EBPb
Figure 1D:方法：hippocampal bilateral injection of C/EBPb antisense oligodeoxynucleotide (b-ODN)
结果：compared to control scrambled ODN (SC-ODN), b-ODN completely disrupted the training-induced IGF-II increase without changing the IGF-II expression in unpaired control rats 24 h after training

Chromatin immunoprecipitation of hippocampal extracts confirmed that C/EBPb binds in vivo to a C/EBPb consensus sequence in the promoter region of the rat IGF-II exon 1 (Supplementary Fig. 4).

方法：Bilateral injections of IGF-II ODN antisense (IGF-II-ODN) were used to selectively knockdownthe IGF-IIexpression in the dorsal hippocampus.

Figure 2A:Injection either immediately or 8 h after training, or at both time points, showed that double, but not single, injections of IGF-II-ODNsignificantly disrupted memory retention at 24 h after training, compared to SC-ODN

IGF-II-ODN doubly injected at 24 and 32 h after training, compared to SC-ODN, significantly disrupted memory retention at 48 h after training (Fig. 2a) and re-training of the amnesic rats resulted in normalmemory retention 24 h after re-training (Fig. 2a), thus excluding hippocampal damage or non-specific effects.
However, IGF-II-ODN doubly injected at 96 and 104 h after training did not affectmemory retention 24 h later (Fig. 2a).

Figure 2B:Theamnesia caused by IGF-II-ODNdouble injections was rescued by the co-administration of recombinant IGF-II, but not IGF-I (Fig. 2b), further proving that IGF-II expression is essential for IA memory consolidation.

问题：whether exogenously administered IGF-II into the hippocampus immediately after training modulates memory
strength.
Figure 3A:The latency cut-off time was raised to 900 s. Bilateral injections of IGF-II immediately after training significantlyand persistently enhanced memory retention at 24 h and 7 days, compared to IGF-I or
vehicle

Figure 3B:Finally, hippocampal injection of IGF-II immediately after training significantly enhanced memory retention tested 3 weeks later when the latency of vehicle-injected rats was not significantly different from acquisition, indicating that IGF-II prevents forgetting

The IGF-II-mediated memory enhancement was dose-dependent (Supplementary Fig. 8): hippocampal injections of 25 or 2.5 ng, like 250 ng, immediately after training incrementally enhanced memory retention at 24 h.

Figure 3C:The IGF-II effect generalized to anothermemory task, contextual fear conditioning.Bilateral hippocampal injectionof IGF-II immediatelyafter contextual-auditory fear conditioning training significantly enhanced contextual fear conditioning retention 24 h later, without affecting auditory fear conditioning tested 48 h after training
Figure 3D:Finally, because IA consolidation also critically involves the amygdala（杏仁核）, we tested the effect of bilateraIGF-II injections into the amygdala immediately after training, but found no effect at testing 24 h later

Figure 4A:Bilateral hippocampal injection of IGF-II 24 h after training had no effect onmemory retention tested at 48 h However, if 24 h after training IGF-II was given after memory retrieval (Test 1),memory retention was significantly enhanced 24 h later

Figure 4B:Bilateral hippocampal injection of IGF-II immediately after retrieval (Test 1), 2 weeks after training, did not change memory retention tested 1 day later, compared to vehicle

Figure 5A:Specific inhibitors of IGF-IIR (anti-IGF-IIR antibody) but not IGF-IR (JB1) co-injected with IGF-II completely abolished the memory enhancement compared to respective controls (Fig. 5a). The inhibitors alone did not affect memory retention (Fig. 5a).

Figure 5B:Similarly to the antisense experiments, compared to control IgG, a single bilateral hippocampal injection of anti-IGF-IIR antibody immediately after training did not affectmemory retention (Fig. 5a), whereas double injections, immediately and 8 h after training, caused a complete amnesia 24 h after training

问题：whether IGF-II-mediated memory enhancement recruits new protein synthesis.



Figure 5C:Bilateral hippocampal co-injection of IGF-II and the protein synthesis inhibitor anisomycin immediately afterTest 1, 24 h after training, showed that anisomycin, compared to vehicle, completely disrupted the IGF-II-mediated memory enhancement tested 24 h later (Fig. 5c) without changing the training-induced retention levels.

Figure 6A:Quantitative western blot analyses confirmed that training significantly increased both pCREB and C/EBPb
levels in the hippocampus 20 h later14 (trained-vehicle vs naive-vehicle, Fig. 6a). Compared to vehicle, IGF-II treatment immediately after training resulted in only a tendency towards a further increase in both markers (Fig. 6a).
Figure 6B: