Nicotinic receptors in the periphery
Nicotinic acetylcholine receptors (nAChRs) belong to the ligand-gated ion channel receptor superfamily: nAChRs are composed of 5 subunits arranged to form an integral ion channel that can open upon binding the neurotransmitter, ACh, or exogenous ligands, such as nicotine. Muscle type nAChRs are found at the neuromuscular junction and in the electric organs of fish. The muscle nAChRs are very well-characterized and will be noted but not discussed in this chapter. More recently, neuronal type nAChRs were identified in neurons in the central and peripheral nervous systems and also in epithelia. The nAChR family is found throughout the central nervous system (CNS), in the peripheral autonomic nervous system, in adrenal chromaffin cells, and also in skin, the cornea, cochlear, and bronchial epithelial cells (Nguyen et al., 2000b). Their functions, which are just beginning to be elucidated, are a subject of intense investigation (Cordero-Erausquin et al., 2000; Wessler et al., 1999).
