Fig. (1).

Intracellular signalling pathways associated to the different mGluR subtypes. Group I mGluRs, including mGluR1 and mGluR5, are positively coupled to phospholipase C (PLC) through activation of a G-protein of the G_q type; in turn, production of innositol triphosphate (IP3), release of Ca²⁺ from intracellular stores and production of diacylglycerol (DAG) activate protein kinase C. Group II and Group III mGluRs are negatively coupled to adenylate cyclase (AC) through G-protein of the G_i/G_o type, leading to decreased formation of cyclic AMP (cAMP).