A new form of long-term depression in the perirhinal cortex

We demonstrate a form of long-term depression (LTD) in the perirhinal corte x that relies on interaction between different glutamate receptors. Group I I metabotropic glutamate (mGlu) receptors facilitated group 1 mGlu receptor -mediated increases in intracellular calcium. This facilitation plus NMDA r eceptor activation may be necessary for induction of LTD at resting membran e potentials. However, depolarization enhanced NMDA receptor function and r emoved the requirement of synergy between group I and group II mGlu recepto rs: under these conditions, activation of only NMDA and group I mGlu recept ors was required for LTD. Such glutamate receptor interactions potentially provide new rules for synaptic plasticity. These forms of LTD occur in the perirhinal cortex, where long-term decreases in neuronal responsiveness may mediate recognition memory.