Which cholinergic receptors are G-protein coupled?

Muscarinic receptors are indeed G-protein coupled receptors, which is essential for their function in the parasympathetic nervous system. When acetylcholine binds to muscarinic receptors, it activates intracellular G-proteins that subsequently influence various signaling pathways, leading to diverse physiological responses such as changes in heart rate, glandular secretion, and smooth muscle contraction.

In contrast, nicotinic receptors are ion channels that mediate fast synaptic transmission by allowing the influx of cations into the cell, leading to depolarization. They do not involve G-protein coupled mechanisms. This key functional difference highlights why muscarinic receptors are categorized as G-protein coupled, while nicotinic receptors are not.

Understanding the role of each receptor type is crucial for grasping how cholinergic signaling influences bodily functions, which is particularly relevant in pharmacology and therapeutic applications.