 Nicotinic acetylcholine receptors are ligand-gated ion channels permeable to sodium, potassium, and calcium ions.In other words, they are ion channels embedded in cell membranes, capable of switching from a closed to an open state when acetylcholine binds to them; in the open state they allow ions to pass through.Nicotinic receptors come in two main types, known as muscle-type and neuronal-type.