<P> Nicotinic acetylcholine receptors, or nAChRs, are receptor proteins that respond to the neurotransmitter acetylcholine . Nicotinic receptors also respond to drugs, including the nicotinic receptor agonist nicotine . They are found in the central and peripheral nervous system, muscle, and many other tissues of many organisms, including humans . At the neuromuscular junction they are the primary receptor in muscle for motor nerve - muscle communication that controls muscle contraction . In the peripheral nervous system: (1) they transmit outgoing signals from the presynaptic to the postsynaptic cells within the sympathetic and parasympathetic nervous system, and (2) they are the receptors found on skeletal muscle that receive acetylcholine released to signal for muscular contraction . In the immune system, nAChRs regulate inflammatory processes and signal through distinct intracellular pathways . In insects, the cholinergic system is limited to the central nervous system . </P> <P> The nicotinic receptors are considered cholinergic receptors, since they respond to acetylcholine . Nicotinic receptors get their name from nicotine, which does not stimulate the muscarinic acetylcholine receptor, but instead selectively binds to the nicotinic receptor . The muscarinic acetylcholine receptor likewise gets its name from a chemical that selectively attaches to that receptor--muscarine . Acetylcholine itself binds to both muscarinic and nicotinic acetylcholine receptors . </P> <P> As ionotropic receptors, nAChRs are directly linked to ion channels . New evidence suggests that these receptors can also use second messengers (as metabotropic receptors do) in some cases . Nicotinic acetylcholine receptors are the best - studied of the ionotropic receptors . </P>

Where are receptors for acetylcholine located at the neuromuscular junction