Translocation and activation of Rac in the hippocampus during associative contextual fear learning.

Small G proteins including Rac are mediators of changes in neuronal morphology associated with synaptic plasticity. Previous studies in our laboratory showed that Rac is highly expressed in the adult mouse hippocampus, a brain area that exhibits robust synaptic plasticity and is crucial for the acquisition of memories. In this study, we investigated whether Rac was involved in NMDA receptor-dependent associative fear learning in the area CA1 of adult mouse hippocampus. We found that Rac translocation and activation was increased in the hippocampus following associative fear conditioning in mice, and that these increases are blocked by intraperitoneal injection of the NMDA receptor channel blocker MK801 at the acquisition stage. Our data indicate that NMDA receptor-dependent associative fear learning alters Rac localization and function in the mouse hippocampus.