Role of metabotropic glutamate receptors in persistent forms of hippocampal plasticity and learning

Storage and processing of information at the synaptic level is enabled by the ability of synapses to persistently alter their efficacy. This phenomenon, known as synaptic plasticity, is believed to underlie multiple forms of long-term memory in the mammalian brain. It has become apparent that the metabotropic glutamate (mGlu) receptor is critically required for both persistent forms of memory and persistent synaptic plasticity. Persistent forms of synaptic plasticity comprise long-term potentiation (LTP) and long-term depression (LTD) that last at least for 4 h but can be followed in vivo for days and weeks. These types of plasticity are believed to be analogous to forms of memory that persist for similar time-spans. The mGlu receptors are delineated into three distinct groups based on their G-protein coupling and agonist affinity and also exercise distinct roles in the way they regulate both long-term plasticity and long-term hippocampus-dependent memory. Here, the mGlu receptors will be reviewed both in general, and in the particular context of their role in persistent (>4 h) forms of hippocampus-dependent synaptic plasticity and memory, as well as forms of synaptic plasticity that have been shown to be directly regulated by memory events. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.