Describing one of the two main classes of acetylcholine receptors, so called because the effect of acetylcholine on them can be mimicked by nicotine. Nicotinic receptors are found at neuromuscular junctions in skeletal muscle and at postganglionic cells in ganglia of both divisions of the vertebrate autonomic nervous system. They are fast-acting receptors containing their own intrinsic ion channel, which is directly activated by the receptor agonists. Compare muscarinic.