What is the effect of alpha1 receptors on phospholipase C?

Alpha-1 adrenergic receptors are G protein-coupled receptors that primarily couple with the Gq protein. When these receptors are activated by their respective ligands, such as norepinephrine or epinephrine, they stimulate the Gq protein pathway.

This activation leads to the activation of phospholipase C (PLC), an enzyme that plays a critical role in signal transduction. Once activated, PLC catalyzes the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) in the membrane, producing two important second messengers: inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 promotes the release of calcium ions from the endoplasmic reticulum, leading to various cellular responses, including muscle contraction, neurotransmitter release, and other physiological effects. Meanwhile, DAG activates protein kinase C (PKC), which also mediates various cellular activities.

Therefore, upon activation of alpha-1 receptors, there is a clear and direct stimulatory effect on phospholipase C, resulting in an increase in intracellular signaling cascades related to calcium mobilization and other responses.