To investigate the role of mGluR8 in modulating the synaptic responses of retinal ganglion cells, we used a recently identified positive allosteric modulator of mGluR8, AZ12216052 (AZ) and the << mGluR8 >>-specific orthosteric agonist [[ (S)-3,4-dicarboxyphenylglycine ]] (DCPG).