Figure 2. Schematic diagram of type-1 metabotropic glutamate receptor (mGluR1)-mediated long-term depression (LTD) at parallel fiber to Purkinje cell synapse.

The long C-terminal domain of mGluR1a is required for inositol trisphosphate (IP ₃)-mediated Ca ²⁺ release and LTD induction. mGluR1b lacking this C-terminal domain cannot drive the cascade for LTD induction. A1R, A ₁-subtype adenosine receptor; AMPAR, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor; DG, diacylglycerol; CaV3.1, Ca _V3.1 T-type voltage-dependent Ca ²⁺ channel; GABA _BR, type-B γ-aminobutyric acid receptor; PIP ₂, phosphatidylinositol 4,5-bisphosphate; PKC, protein kinase C; PLC, phospholipase C; PQ, P/Q-type voltage-dependent Ca ²⁺ channel.