Cognitive deficits are the core symptoms of schizophrenia. Spine deficits have been found in hippocampus of schizophrenia patients, and were associated with cognitive impairments. N-methyl-D-asparate receptors (NMDARs) had been known to play a critical role in synaptic pruning and stabilization during adolescence. In the present study, male adolescent rats were exposed to dizocilpine (MK-801) (0.2mg/kg i.p qd) or 0.9% saline for 14 days. Then spatial memory, spine morphological changes and RhoA, Rac1, Cdc42 mRNA levels in hippocampus were measured. As a result, MK-801 impaired spatial memory in the adolescent rats, as well as reduced the proportion of mushroom spines and increased the proportion of stubby spines in hippocampus. MK-801 also reduced the expression levels of Rac1 and Cdc42 mRNA and upregulated RhoA mRNA in hippocampus. These results imply that subchronic MK-801 administration during adolescence might disturb the expression of RhoA, Rac1 and Cdc42 mRNA, and then lead to the decay of the spines in hippocampus, which could be involved in cognitive impairments in schizophrenia.