Reduction of Ca(v)1.3 channels in dorsal hippocampus impairs the development of dentate gyrus newborn neurons and hippocampal-dependent memory tasks

Ca(v)1.3 has been suggested to mediate hippocampal neurogenesis of adult mice and contribute to hippocampal-dependent learning and memory processes. However, the mechanism of Ca(v)1.3 contribution in these processes is unclear. Here, roles of Ca(v)1.3 of mouse dorsal hippocampus during newborn cell development were examined. We find that knock-out (KO) of Ca(v)1.3 resulted in the reduction of survival of newborn neurons at 28 days old after mitosis. The retroviral eGFP expression showed that both dendritic complexity and the number and length of mossy fiber bouton (MFB) filopodia of newborn neurons at ≥ 14 days old were significantly reduced in KO mice. Both contextual fear conditioning (CFC) and object-location recognition tasks were impaired in recent (1 day) memory test while passive avoidance task was impaired only in remote (≥ 20 days) memory in KO mice. Results using adeno-associated virus (AAV)-mediated Ca(v)1.3 knock-down (KD) or retrovirus-mediated KD in dorsal hippocampal DG area showed that the recent memory of CFC was impaired in both KD mice but the remote memory was impaired only in AAV KD mice, suggesting that Ca(v)1.3 of mature neurons play important roles in both recent and remote CFC memory while Ca(v)1.3 in newborn neurons is selectively involved in the recent CFC memory process. Meanwhile, AAV KD of Ca(v)1.3 in ventral hippocampal area has no effect on the recent CFC memory. In conclusion, the results suggest that Ca(v)1.3 in newborn neurons of dorsal hippocampus is involved in the survival of newborn neurons while mediating developments of dendritic and axonal processes of newborn cells and plays a role in the memory process differentially depending on the stage of maturation and the type of learning task.