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 couples neuronal n - methyl - d - aspartate receptors 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 .