A method of inhibiting the binding between N-methyl-D-aspartate receptors and neuronal proteins in a neuron the method comprising administering to the neuron an effective inhibiting amount of a peptide replacement agent for the NMDA receptor or neuronal protein interaction domain that effect said inhibition of the NMDA receptor neuronal protein. The method is of value in reducing the damaging effect of injury to mammalian cells. Postsynaptic density-95 protein (PSD-95) couples neuronal N-methyl-D-aspartate receptors (NMDARs) to pathways mediating excitotoxicity and ischemic brain damage. This coupling was disrupted by transducing neurons with peptides that bind to modular domains on either side of the PSD-95/NMDAR interaction complex. This treatment attenuated downstream NMDAR signaling without blocking NMDAR activity, protected cultured cortical neurons from excitotoxic insults and dramatically reduced cerebral infarction volume in rats subjected to transient focal cerebral ischemia. The treatment was effective when applied either before, or one hour after, the onset of excitotoxicity in vitro and cerebral ischemia in vivo. This approach prevents negative consequences associated with blocking NMDAR activity and constitutes practical therapy for stroke.