FIGURE 7.

Schematics of the data interpretation. (A) During excitotoxic episodes Glu activates both extrasynaptic GluN2B-containng NMDARs and synaptic GluN2A-containing NMDARs. Entry of external Ca²⁺ into neurons through open NMDAR channels causes intracellular Ca²⁺ overload. (B) During hyperhomocysteinemia HCY desensitizes extrasynaptic GluN2B-containng NMDARs limiting intracellular Ca²⁺ accumulation in the extrasynaptic regions. Synaptic GluN2A-containing NMDARs are kept activated by HCY that allows intracellular Ca²⁺ accumulation in post-synaptic regions and presynaptic terminal inducing synaptic Ca²⁺ oscillations.