Metabotropic Glutamate Receptor Function in Thalamocortical Circuitry

Abstract

The thalamo-corticothalamic network underpins sensory, motor and cognitive processing. All three of the mGlu receptor groups are represented in these pathways. Of the Group I receptors, it seems clear that mGlu1 receptors are located postsynaptically to corticothalamic terminals on dendrites of thalamic relay cells and may function to modulate relay cell transmission under various conditions. Group III mGlu receptors (mGlu4, mGlu7, mGlu8) may also modulate this synapse via a presynaptic mechanism. GABAergic inhibitory processes can be modulated via activation of either Group II (mGlu2 and mGlu3) receptors or Group III receptors, acting either on GABAergic terminals or on thalamic cell bodies, including those in the thalamic reticular nucleus (TRN). There is also evidence that mGlu receptors can modulate astrocyte function in the thalamus. The heterogeneous expression of mGlu receptors at specific sites within the thalamus makes them potential therapeutic targets for a variety of conditions including pain, epilepsy and cognitive disorders.