Neuronal cholinergic nicotinic receptors (CHRNs) are a heterogeneous class of cation (positively charged) channels expressed in the central and peripheral nervous system. There are 11 neuronal CHRN genes, each of which encodes a receptor subunit. The neuronally expressed nicotinic receptors consist of combinations of alpha and beta subunits, encoded in humans by 8 alpha (α2-α 7, α9-α10) and 3 beta (β2-β4) genes [8]. These subunits form homo- or hetero-pentameric subtypes, which are present in various regions throughout the nervous system. To form a receptor, five subunits must be combined within the cell and the specific combination of these subunits defines the receptor subtype.
