Nicotinic acetylcholine receptor

Nicotinic acetylcholine receptors, or nAChRs, are neuron receptor proteins that respond to the neurotransmitter acetylcholine. Nicotonic receptors also respond to drugs, including the nicotinic receptor agonist nicotine. They are found in the central nervous system of humans, and also play two important roles 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. Nicotinic receptors are also found in other creatures. In insects, the cholinergic system is limited to the central nervous system.

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.

Alpha-4 beta-2 nicotinic receptor

The alpha-4 beta-2 nicotinic receptor, also known as the α₄β₂ receptor, is a type of nicotinic acetylcholine receptor implicated in learning, consisting of α₄ and β₂ subunits. It is located in the brain, where activation yields post- and presynaptic excitation, mainly by increased Na⁺ and K⁺ permeability.

Stimulation of this receptor subtype is also associated with growth hormone secretion. People with the inactive CHRNA4 mutation Ser248Phe are an average of 10 cm (4 inches) shorter than average and predisposed to obesity.

The receptors exist in the two stoichiometries:

Ligands

Agonists

Alpha-3 beta-4 nicotinic receptor

The alpha-3 beta-4 nicotinic receptor, also known as the α₃β₄ receptor, is a type of nicotinic acetylcholine receptor, consisting of α₃ and β₄ subunits. It is located in the autonomic ganglia and adrenal medulla, where activation yields post- and/or presynaptic excitation.

As with other nicotinic acetylcholine receptors, the α₃β₄ receptor is pentameric [(α₃)_m(β₄)_n where m + n = 5]. The exact subunit stoichiometry is not known and it is possible that more than one functional α₃β₄ receptor assembles in vivo with varying subunit stoichiometries.

Ligands

Agonists

Antagonists

Competitive

Noncompetitive