Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels which exhibit considerable subunit diversity. In addition to nAChR subunits expressed at the neuromuscular junction (α1, β1, γ, δ and ε), twelve neuronal nAChR subunits (α2-α10 and β2-β4) have been identified which coassemble to generate a diverse family of nAChRs. Neuronal nAChRs are expressed both in the central and peripheral nervous system and have been implicated in processes such as synaptic transmission and modulation of neurotransmitter release. Neuronal nAChRs have been implicated in several neurological disorders and are seen as important targets for therapeutic drug discovery. 5-hydroxytryptamine type 3 receptors (5HT3Rs) are related members of the same superfamily. In an attempt to overcome problems of inefficient expression of nAChRs in heterologous expression systems, chimeric subunits were created from both nAChRs and 5HT3Rs. A series of subunits chimeras has been constructed which contain regions from nAChR and 5HT3R subunits. By expression of wild-type and chimeric subunits, we have examined the influence of nAChR and 5HT3R subunit domains upon receptor targeting, trafficking and functional properties.Studies in mammalian cell lines have demonstrated the importance of transmembrane domains for efficient subunit folding, receptor assembly and cell-surface expression. Electrophysiological studies of receptors assembled from α7/5HT3A subunit chimeras have revealed the influence of subunit domains upon ion channel properties such as rectification, desensitisation and conductance. Evidence has been obtained to indicate that both extracellular and cytoplasmic domains exert a dramatic and significant influence upon single-channel conductance. These data support a role for regions other than hydrophobic transmembrane domains in determining ion channel properties. A further series of subunit chimeras has been constructed with the aim of investigating the influence of the large cytoplasmic loop domain (between transmembrane regions M3 and M4) on receptor targeting and trafficking. Evidence from expression in polarised cells has shown that the intracellular loop region of several nAChR subunits can markedly influence subunit folding, assembly, cell-surface expression and intracellular targeting. Additionally, these intracellular loop chimeras have provided further evidence that this non-transmembrane region exerts a dramatic influence upon functional properties such as single-channel conductance. These M3-M4 loop chimeras are useful tools with which to investigate the influence of subunit domains upon interactions with intracellular proteins.