Induction of NMDA receptor-dependent long-term depression in visual cortexdoes not require metabotropic glutamate receptors

We tested the role of group I mGluRs in the induction of long-term depressi on (LTD) in the visual cortex, using the novel mGluR antagonist LY341495 an d mice lacking mGluR5, the predominant phosphoinositide (PI)-linked mGluR i n the visual cortex. We find that LY341495 is a potent blocker of glutamate -stimulated PI hydrolysis in visual cortical synaptoneurosomes, and that it effectively antagonizes the actions of the mGluR agonist 1S,3R-aminocyclop entane-1,3-dicarboxylic acid (ACPD) on synaptic transmission in visual cort ical slices. However, LY341495 has no effect on the induction of LTD by low -frequency stimulation. Furthermore, mice lacking mGluR5 show normal NMDA r eceptor-dependent LTD. These results indicate that group I mGluR activation is not required for the induction of NMDA receptor-dependent LTD in the vi sual cortex.