nAChRs are formed by the assembly of five transmembrane subunits, selected from a pool of 17 homologous polypeptides (α1-10, β1-4, γ, δ, and ε). There are many nAChR subtypes, each consisting of a specific combination of subunits, which mediate diverse physiological functions. They are widely expressed in the central nervous system, while, in the periphery, they mediate synaptic transmission at the neuromuscular junction and ganglia. nAChRs are also found in non-neuronal/non-muscle cells (keratinocytes, epithelia, macrophages, etc. ). Structurally, all subunits have the following: a conserved large extracellular N-terminal domain, conserved transmembrane domains, a variable cytoplasmic loop and a fourth transmembrane domain with a short extracellular C-terminal domain. An active nAChR is generally a heteropentamer of these various subunits organized around a central pore