Alterations of Emotional and Cognitive Behaviors in Matrix Metalloproteinase-2 and -9-Deficient Mice

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 activity- dependent synaptic plasticity and brain development.