Changes in emotional state are known to alter neuronal excitability and can modify learning and memory formation. Such experience-dependent neuronal plasticity can be long-lasting and is thought to involve the regulation of gene transcription. We found that a single fear-inducing stimulus increased GluR2 (also known as Gria2) mRNA abundance and promoted synaptic incorporation of GluR2-containing AMPA receptors (AMPARs) in mouse cerebellar stellate cells. The switch in synaptic AMPAR phenotype was mediated by noradrenaline and action potential prolongation. The subsequent rise in intracellular Ca 2+ and activation of Ca 2+-sensitive ERK/MAPK signaling triggered new GluR2 gene transcription and a switch in the synaptic AMPAR phenotype from GluR2-lacking, Ca 2+-permeable receptors to GluR2-containing, Ca 2+-impermeable receptors on the order of hours. The change in glutamate receptor phenotype altered synaptic efficacy in cerebellar stellate cells. Thus, a single fear-inducing stimulus can induce a long-term change in synaptic receptor phenotype and may alter the activity of an inhibitory neural network.
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