Acetylcholine-activated channels are

• A. Inhibited by acetylcholine
• B. Activated by acetylcholine; Gi-protein coupled
• C. Voltage-gated potassium channels
• D. Calcium-activated channels

Answer: (B)

Acetylcholine-activated channels are ligand-gated ion channels that open directly in response to acetylcholine binding, allowing cations (primarily Na+ and some K+) to pass and produce depolarization. This describes the nicotinic acetylcholine receptor, which is fast and ionotropic. They are not inhibited by acetylcholine, nor are they voltage-gated or calcium-activated—their gating depends on ligand binding, not changes in voltage or intracellular calcium. The muscarinic acetylcholine receptors, which are GPCRs that can modulate ion channels via G-proteins like Gi, are a different mechanism; the channels themselves here are not Gi-coupled ligand-gated channels. So the correct idea is that acetylcholine activates these channels directly through binding, leading to ion flow and depolarization.