IP3 is second messenger

• Phospholipase C and PLC beta 3 Gq

Receptors that activate this pathway (Phospholipase C) are mainly G protein-coupled receptors coupled to the Gαq subunit, including:

• 5-HT2 serotonergic receptors (5-hydroxytryptamine receptor#Structural highlights/Specific Function of 5-HT2B).
• α1 adrenergic receptors
• Calcitonin receptors
• Histamine H1 receptor. The H1 receptor is a histamine receptor belonging to the family of rhodopsin-like G-protein-coupled receptors. The H1 receptor is linked to an intracellular G-protein (Gq) that activates phospholipase C and the inositol triphosphate signaling pathway. When a ligand binds to a G protein-coupled receptor that is coupled to a Gq heterotrimeric G protein, the α-subunit of Gq can bind to and induce activity in the PLC isozyme PLC-β, which results in the cleavage of PIP2 into IP3 and DAG.
• Metabotropic glutamate receptor 1 and metabotropic glutamate receptor 5 belong to group I and activate phospholipase C. For details see Metabotropic glutamate receptor 5.
• M1, M3, and M5 muscarinic receptors. Muscarinic acetylcholine receptors (mAChR) contain 5 subtypes M1-M5. Subtypes M1, M3, M5 activate phospholipase C which leads to activation of protein kinase C.
• Inositol 1,4,5-Trisphosphate Receptor