Arc protein is not found in presynaptic terminals or axons but is highly expressed in dendrites [7,8], the postsynaptic density [7,9,10] and the nucleus [11,12]. Arc regulates endocytosis of a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs) [13,14], Notch signaling [15], and spine size and type [16].