Acetylcholine Nicotinic Receptors
Nicotinic receptors (nAChRs) are ligand-gated ion channels that modulate cell membrane potentials. Each receptor is composed of pentameric combinations of subunits (α1-10, β1-4, δ, ε and γ). Nicotinic receptors are generally divided into three functional classes: muscle subunits (α1, β1, δ, ε, γ), standard neuronal subunits (α1-6 and β2-4) that form in pairwise αβ combinations, and subunits (α7-9) that can form homomeric nAChRs. Neuronal nicotinic receptors are found in the central nervous system and in autonomic ganglia where they regulate processes such as transmitter release, cell excitability and neuronal integration. Nicotinic receptors located at the neuromuscular junctions of somatic muscles are responsible for muscular contraction.