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. 2014 Mar 12;39(8):1880–1892. doi: 10.1038/npp.2014.35

Figure 5.

Figure 5

Ventral, but not dorsal, hippocampus was involved in synaptic consolidation of contextual memory. (a) Schematic representation of viral delivery to the dorsal hippocampus (dHPC), ventral hippocampus (vHPC), or both (HPC). CaMKIIα::HA-hM4Di-IRES-mCitrine or CaMKIIα::EGFP viral vectors were bilaterally injected into dHPC, vHPC, or both. (b) Immunostaining of mouse brain delivered with CaMKIIα::HA-hM4Di-IRES-mCitrine virus. HA-hM4Di was expressed in the dorsal hippocampus, ventral hippocampus, or both in hM4Di-dHPC, hM4Di-vHPC, or hM4Di-HPC mice, respectively. Scale bar: 1 mm. (c) Ventral, but not dorsal, hippocampus was involved in synaptic consolidation of contextual memory. Three weeks after viral delivery, animals were trained and administrated with three doses of clozapine-n-oxide (CNO; 2 mg/kg) at 0, 2, and 4 h after training. Contextual and cued memories were tested 24 and 48 h later, respectively. Mice with HA-hM4Di viruses injected into both dHPC and vHPC showed a significant decrease in contextual memory compared with the control mice (p=0.047, n=8). Mice with HA-hM4Di viruses injected into only vHPC showed a significant decrease in contextual memory (p=0.015, n=10). However, mice with HA-hM4Di virus injected into only dHPC showed a similar freezing compared with the control mice in contextual memory (p=0.795, n=7). (d) Synaptic consolidation was not impaired by administration of CNO before training in hM4Di-vHPC mice. HA-hM4Di viruses were delivered to the vHPC. Three weeks later, mice were administrated with CNO (2 mg/kg) 30 min before, instead of after training. There was no significant difference in contextual memory between hM4Di-vHPC and control mice (p=0.87, n=9).