Inositol is a six-carbon sugar related to glucose, released on binding of certain neurotransmitters or hormones. Inositol triphosphate (IP3) is formed as a second messenger, along with diacylglycerol (DG), by cleavage of the membrane phospholipid PIP2. IP3 triggers the release of Ca+, which can lead to an array of cascading responses, and DG activates a protein kinase.