Structure and function of neuronal nicotinic acetylcholine receptors.
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abstract
This chapter discusses some aspects of neuronal acetylcholine receptors (AChRs), reviews some of the recent studies of the mechanism by which chronic exposure to nicotine affects a42 AChRs, and describes some of the pharmacological properties of neuronal AChRs, especially the differences between 7 and 8 AChRs and the usefulness of epibatidine (exo-2-(6-chloro-3-pyridyl)-7-azabicyclo-[2.2.l]-heptane) as a ligand for many types of neuronal AChRs. The basic homologies in structure of receptors in this superfamily have been illustrated in the chapter. Homologies in overall domain relationships are demonstrated by showing that functional mosaics could be made in which the large N-terminal extracellular domain of 7 AChRs could be grafted just before the first transmembrane domain to the C-terminal part of 5HT3 receptors. This resulted in receptors with acetylcholine-gated cation channels having the ion selectivity of 5HT3 receptors. Close similarities in the overall structures of the ion channels are demonstrated by showing that changing only three amino acids in the sequence lining the cation-specific channel of excitatory 7 neuronal AChRs to amino acids typical of the anion-specific channels of inhibitory glycine or GABAA receptors changed the ion selectivity of the mutated a7 AChR channels from cations to anions
