Final answer:
The most common nicotinic ACh receptor in the CNS is the ligand-gated ion channel type, which is activated by ACh or nicotine, causing depolarization of the postsynaptic membrane.
Step-by-step explanation:
The most common nicotinic acetylcholine (ACh) receptor in the central nervous system (CNS) is the ligand-gated ion channel type. This receptor is crucial for synaptic transmission within the CNS. Nicotinic receptors are activated when ACh or nicotine bind to them. These receptors are distinct from muscarinic receptors, which are G-protein-coupled receptors and do not have cross-reactivity with nicotinic receptors. For instance, while nicotine can activate nicotinic receptors, it will not bind to muscarinic receptors, and vice versa for muscarine.
At autonomic ganglia, whether sympathetic or parasympathetic, all ganglionic neurons have nicotinic receptors on their cell membranes. These receptors are responsible for the depolarization of the postsynaptic membrane, facilitated by the influx of positive ions through the ligand-gated cation channel.