L-Glutamate is the predominant excitatory neurotransmitter in vertebrate nervous systems. Receptors for glutamate have been implicated in neuronal plasticity and higher neuronal functions like memory and learning. The ligand gated ionotropic glutamate receptor subtypes are traditionally defined by specific agonists. Currently four genes (GluR A, B, C and D) are known that code for the AMPA subtypes of glutamate receptors. Recombinant expression of wild type and mutated sequences identified a critical residue in the putative TM2 channel-lining segment that controls Ca2+ ion permeability. The arginine (R) found in GluR B subunits at that position renders AMPA channels impermeable for Ca2+ ions, whereas glutamine (Q) containing GluR A, C and D subunits give rise to Ca2+ permeable channels. Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS), and glutamate takes its effect in the CNS through metabotropic and ionotropic glutamate receptors (mGluRs and iGluRs, respectively). Genome-wide and candidate gene association study indicated that glutamate receptors (GluRs) were implicated in ADHD.


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