mGluR1-signaling protein complexes from mGluR1a-rescue and mGluR1b-rescue cerebella. A, Expression levels of mGluR1 proteins in the cerebella of WT, mGluR1-KO (KO), mGluR1a-rescue (1a rescue), and mGluR1b-rescue (1b rescue) mice. Synaptosomal fractions were prepared from mouse cerebella at P15 and in adulthood and were immunoblotted with an antibody specific to the extracellular domain of mGluR1 proteins. Arrowheads indicate bands for mGluR1a (1a) and mGluR1b (1b). B, Composition of mGluR1-signaling protein complex. Synaptosomal fraction from the cerebellum of each genotype was incubated with rat monoclonal antibody against the extracellular domain of mGluR1 or rat IgG. Subsequently, the input (in) and the proteins bound to mGluR1 antibody (mG) and IgG (Ig) were immunoblotted using antibodies against the N-terminal domain of mGluR1, Homer, GluRδ2, GABA_BR2, and Ca_v2.1.