Matrix metalloproteinases (MMPs) function to remodel the pericellular environment, and thereby play a crucial
role in the remodeling of neural circuits. In the present study, we investigated the role of MMP-2 and MMP-9 in
emotional and cognitive function using mice with targeted deletions of the MMP-2 and MMP-9 genes. Emotional
behaviors of MMP-9-(-/-) mice but not MMP-2-(-/-) mice were altered, which was manifested in performances in the
open-field and elevated plus-arm maze tests. MMP-9-(-/-) mice showed impairments in long-term object recognition
memory and conditioned fear memory. MMP-2-(-/-) mice had no deficits in learning and memory. These findings suggest
that endogenous MMP-9 play a role in emotional and cognitive behaviors, which may possibly be related to activitydependent
synaptic plasticity and brain development.