Final answer:
The muscarinic receptors have five subtypes: M1, M2, M3, M4, and M5. M2 and M4 inhibit adenylate cyclase, while M1, M3, and M5 activate phospholipase C. This affects various cellular functions through secondary messengers like calcium and cAMP.
Step-by-step explanation:
The correct option : c
There are five subtypes of muscarinic receptors: M1, M2, M3, M4, and M5. Among these, M2 and M4 are known to inhibit adenylate cyclase via Gi proteins, whereas M1, M3, and M5 can activate phospholipase C (PLC) via Gq proteins. This leads to the generation of inositol triphosphate (IP3) and diacylglycerol (DAG) as secondary messengers, subsequently raising intracellular calcium levels and activating protein kinase C (PKC), respectively. Let's delve into the muscarinic receptors' impact on signaling pathways. Muscarinic receptors are a type of G protein-coupled receptor (GPCR) that respond to the neurotransmitter acetylcholine. They play a key role in the functioning of the parasympathetic nervous system by modulating a variety of physiological processes.
When the M2 and M4 receptors inhibit adenylate cyclase, this results in a decrease in cyclic adenosine monophosphate (cAMP) levels, influencing cellular functions such as cardiac muscle contraction and neurotransmitter release. On the other hand, when M1, M3, and M5 activate phospholipase C, the resulting mobilization of calcium ions and activation of PKC lead to diverse downstream effects including smooth muscle contraction and glandular secretion. There are five subtypes of muscarinic receptors; M1, M2, M3, M4, and M5, which affect phospholipase, with the M2 and M4 subtypes additionally affecting adenylate cyclase.