AMPA receptors consist of four closely related genes with about 70% homology that encode the four subunits GluR1-4. Their expression is known to be developmentally regulated2 and are also known to undergo alternative splicing. In fact, all four receptors have two splice variants, termed flip and flop, in an extracellular region adjacent to the M4 transmembrane region3. These splice variants are also developmentally regulated such that flip is expressed before birth and remains highly expressed throughout adulthood whereas flop expression is postnatal and reaches flip’s level in adulthood.AMPA receptors are highly expressed in the brain. However, the GluR4 subunit is present in lower amounts in the CNS, except in the reticular thalamic neuclei and the cerebellum
