The 5-HT 3 receptor belongs to the Cys-loop superfamily of ligand-gated ion channels (LGICs) and therefore differs structurally and functionally from all other 5-HT receptors (5-hydroxytryptamine, or serotonin) receptors which are G protein-coupled receptors. This ion channel is cation-selective and mediates neuronal depolarization and excitation within the central and peripheral nervous systems.
The epithelial sodium channels (ENaC) are located on the apical membrane of epithelial cells in the distal kidney tubules, lung, respiratory tract, male and female reproductive tracts, sweat and salivary glands, placenta, colon and some other organs [3,5,7].
Fast-responding GABA receptors are members of a family of Cys-loop ligand-gated ion channels. Members of this superfamily, which includes nicotinic acetylcholine receptors, GABA A receptors, glycine and 5-HT 3 receptors, possess a characteristic loop formed by a disulfide bond between two cysteine residues.
The inhibitory glycine receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on Glycine Receptors) is a member of the Cys-loop superfamily of transmitter-gated ion channels that includes the zinc activated channels, GABA A, nicotinic acetylcholine and 5-HT 3 receptors .
Therefore, ionotropic receptors are “ligand-gated transmembrane ion channels”. The ions that can travel through ionotropic receptors are generally limited to K+, Na+, Cl-, and Ca2+. Metabotropic receptors. Metabotropic receptors do not have a “channel” that opens or closes.
Inositol trisphosphate receptor (InsP3R) is a membrane glycoprotein complex acting as a Ca 2+ channel activated by inositol trisphosphate (InsP3). InsP3R is very diverse among organisms, and is necessary for the control of cellular and physiological processes including cell division, cell proliferation, apoptosis, fertilization, development, behavior, learning and memory.
The muscarinic acetylcholine receptor likewise gets its name from a chemical that selectively attaches to that receptor — muscarine. Acetylcholine itself binds to both muscarinic and nicotinic acetylcholine receptors. As ionotropic receptors, nAChRs are directly linked to ion channels.