Abstract: The present invention is based on the discovery that neuronal pentraxins play a role in the clustering and internalization of AMPA receptors, synaptogenesis, and metabotropic glutamate receptor-mediated long term depression (LTD) of a synapse. Accordingly, there are provided methods of identifying compounds that that modulate mGluR-mediated AMPA receptor internalization and LTD. Further provided are cleavage products of a member of the neuronal pentraxin family, neuronal pentraxin receptor (NPR). Also provided are isolated peptides comprising the Narp association regions 1 and 2 (NAR1 and NAR2, respectively) and the Narp binding motif (NBM) of AMPA receptors. Finally, there are provided antibodies that block binding of neuronal pentraxins to AMPA receptors, in particular, antibodies that bind NAR1, or NAR2, or NBM.