As stated above, adult forebrain GluN2B (protein and mRNA) levels are unaltered in GluN2B+/+ versus GluN2B2A(CTR)/2A(CTR) mice ( Figure 3A). We also specifically studied GluN2B levels in isolated protein GSK126 mouse fractions enriched in synaptic and peri/extrasynaptic

NMDARs, following an established protocol ( Milnerwood et al., 2010). Briefly, a synaptosomal preparation was made from the hippocampi of adult GluN2B+/+ and GluN2B2A(CTR)/2A(CTR) mice. This prep was then split into a Triton-soluble “non-PSD enriched” fraction including extrasynaptic NMDARs, plus a Triton-insoluble (but SDS-soluble) “PSD-enriched” fraction containing synaptic NMDARs. We found no differences in the levels of GluN2B between GluN2B+/+ and GluN2B2A(CTR)/2A(CTR) Hydroxychloroquine order hippocampi with regard to either total homogenate, “Non-PSD enriched” fraction, or “PSD-enriched” fraction ( Figure 3B). This biochemical

data is in agreement with observations that the NMDAR:AMPAR current ratios in evoked EPSCs measured at holding potentials of −80 and +40 mV are not altered in adult CA1 pyramidal cells of GluN2B2A(CTR)/2A(CTR) mutants compared to GluN2B+/+ controls (Thomas O’Dell, personal communication). Moreover, the decay time constant of NMDAR-mediated EPSCs recorded at +40 mV in GluN2B2A(CRT)/2A(CTR) mutants was found to be indistinguishable from GluN2B+/+ controls (Thomas O’Dell, personal communication), indicative of a similar GluN2 subunit composition. To promote excitotoxic neuronal loss, we stereotaxically

injected a small (15 nmol) dose of NMDA into the hippocampus (just below the dorsal region of the CA1 layer) and quantified the resulting lesion volume 24 hr later. Consistent Resveratrol with the position of the injection site, the lesions were centered on the CA1 subregion, an effect potentially enhanced by the known vulnerability of this subregion to excitotoxic insults (Stanika et al., 2010). However the lesion also spread to other hippocampal subregions (CA3, dentate gyrus) as well as a small intrusion into the thalamus. Importantly, analysis revealed that GluN2B2A(CTR)/2A(CTR) mice exhibited smaller lesion volumes in the hippocampus and the thalamic region (and smaller overall lesion volumes) than GluN2B+/+ mice ( Figures 3C–3F). Thus, the GluN2 CTD subtype also influences NMDAR-mediated excitotoxicity in vivo. We next investigated the mechanistic basis for the observed GluN2 CTD subtype-dependent differences in vulnerability to excitotoxicity. NMDAR-dependent activation of CREB-dependent gene expression protects against excitotoxicity (Lee et al., 2005) and can act as a protective response to excitotoxic insults (Mabuchi et al., 2001). We found that basal levels of CREB (serine-133) phosphorylation (normalized to total CREB) were unaltered in GluN2B2A(CTR)/2A(CTR) neurons (118% ± 12% compared to GluN2B+/+ neurons, p = 0.2).

No related posts.