Postsynaptic density-95 (PSD-95) is a scaffolding protein at excitatory synapses linking N-methyl-D-aspartate receptor (NMDAR) with neuronal nitric oxide synthase (nNOS),which contributes many physiological and pathological actions.We here investigated the spatiotemporal expressions of PSD-95 in spinal cord after contusion and sciatic nerve after crush with real-time PCR and Western blot.The interaction and colocalization between PSD-95 and nNOS after injury were also assessed by coimmmunoprecipates and double immunofluorescent staining,respectively.After spinal cord contusion (SCC),the mRNA and protein for PSD-95 expression were significantly increased at 2 h,and then gradually declined to the baseline level,ultimately upregulated again at 7 d for its gene level and 14 d for its protein level.PSD-95 immunoreactivity (IR) was found in NeuN-IR neurons,CNPase-IR oligodendrocytes,and synapsin-IR synapse punctas,but not in OX-42-IR microglias of spinal cord tissues within 5 mm from the lesion site.Injury-induced expression of PSD-95 was co-immunoprecipitated and co-labeled by nNOS antibody.