We next tested whether the activity-dependent switch-induction mechanism in mouse shares a similar signaling pathway with rat. The NR2B to NR2A switch was blocked by MTEP, U73122, or AP5 (Figures 4D–4K), demonstrating that, like rat, the induction depends on NMDARs, mGluR5, and PLC activation. Moreover, we also tested the mouse induction protocol in rat hippocampal slices and found that it also robustly evoked changes in NMDAR EPSC kinetics and ifenprodil (Figure S7). Next, we examined whether the activity-dependent NR2 subunit switch was deficient in mGluR5 knockout mice. We compared slices from knockout and heterozygous littermates with the experimenter Quisinostat ic50 blind

to genotype. In hippocampal slices from heterozygotes, the high-frequency induction protocol caused a similar speeding of NMDA EPSC decay kinetics and reduction in ifenprodil sensitivity, similar to that observed in wild-types (Figures 5A–5C,

5G, and 5H). However, in slices from the mGluR5 knockouts, although small variable changes in NMDA EPSC decay and ifenprodil sensitivity occurred in some experiments following the induction protocol, no significant change in either of these parameters was observed (Figures 5D–5H). If the activity-dependent switch underlies the developmental regulation of NR2B/NR2A in vivo, a prediction is that the mGluR5 knockout mice should have altered regulation of NR2 subunit composition Apoptosis Compound Library manufacturer in vivo during development. We investigated this possibility by comparing kinetics

and ifenprodil sensitivity of NMDA EPSCs in mGluR5 knockout mice and wild-type littermates. At P15–P18, NMDA EPSCs from CA1 pyramidal cells in wild-type exhibited faster kinetics and a lower sensitivity to ifenprodil compared to knockouts (Figures 6A–6D). However, in the knockouts there was still a considerable speeding in NMDA EPSC kinetics and reduction in ifenprodil sensitivity during development. Therefore, these findings show that there is a deficit these in the developmental switch from NR2B- to NR2A-containing NMDARs in the mGluR5 knockout, demonstrating a role for mGluR5 in this process. However, our data also show that additional mechanisms can at least partly support the developmental switch in the absence of mGluR5. The developmental switch from NR2B to NR2A-containing NMDARs is particularly prominent in primary sensory cortex where it has been shown to depend upon sensory experience. Particularly well studied is this process in primary visual cortex of rodents where visual experience for as little as 1 hr has been shown to drive the switch from NR2B to NR2A in dark-reared animals (Philpot et al., 2001 and Quinlan et al., 1999), and such regulation influences metaplasticity and is required for maturation of receptive fields (Cho et al., 2009, Philpot et al., 2003 and Philpot et al., 2007).