Which muscarinic receptors are known to activate phospholipase C?

Muscarinic receptors are a class of G protein-coupled receptors that mediate a variety of physiological responses to acetylcholine. Specifically, the M1 and M3 receptors are known to activate phospholipase C (PLC). When acetylcholine binds to these receptors, they stimulate the Gq protein, which in turn activates PLC. This activation leads to the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG), resulting in an increase in intracellular calcium levels and further downstream signaling events that are crucial for many cellular functions.

In the context of the question, it is important to highlight that M1 receptors are primarily found in the central nervous system and in glands, whereas M3 receptors are located on smooth muscle and gland tissues, contributing to various autonomic responses, such as glandular secretion and smooth muscle contraction.

While other muscarinic receptors, such as M2 and M4, primarily inhibit adenylate cyclase activity (mediating effects through the G_i protein), they are not involved in the activation of PLC. Therefore, the choice of M1 and M3