Gq family members of heterotrimeric G protein activate beta isoforms of phospholipase C that hydrolyzes phosphatidylinositol phosphate to diacylglycerol and inositol trisphosphate, leading to the protein kinase C activation and intracellular Ca(2+) mobilization, respectively. To understand the functions and regulatory mechanisms of Gq-signaling pathways, we first introduce the Galphaq-interacting proteins, which function as the effectors and the modulators of Gq. Next, we describe the Pasteurella multocida toxin and YM-254890, which are useful tools to investigate Gq signaling as activator and inhibitor, respectively. Finally, we discuss the physiological function of Gq in developmental brain, especially in neural progenitor cells.