Cholinergic receptors nicotinic subunits
cholinergic receptors nicotinic subunits
Nicotinic acetylcholine receptors, or nAChRs, are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the presynaptic and postsynaptic sides of the neuromuscular junction. As ionotropic receptors, nAChRs are directly linked to ion channels and do not use second messengers (as metabotropic receptors do). Nicotinic acetylcholine receptors are the best-studied of the ionotropic receptors.   Like the other type of acetylcholine receptor - muscarinic acetylcholine receptor (mAChR) - nAChR is triggered by the binding of the neurotransmitter acetylcholine (ACh). Just as muscarinic receptors are named such because they are also activated by muscarine, nicotinic receptors can be opened not only by acetylcholine but also by nicotine âhence the name 'nicotinic.'   In insects, the cholinergic system is limited to the central nervous system. In contrast, neuronal receptors are found in both the central nervous system and the peripheral nervous system of mammals. Mammalian neuromuscular receptors are found in the neuromuscular junctions of somatic muscles ; stimulation of these receptors causes muscular contraction.