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5-HT3 receptor
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<p>The 5-HT3 receptor belongs to the <a href="/facts/Cys-loop_superfamily/bUb7Uuo0">Cys-loop superfamily</a> of <a href="/facts/Ligand-gated_ion_channels/gN9RkNC2">ligand-gated ion channels</a> (LGICs) and therefore differs structurally and functionally from all other <a href="/facts/5-HT_receptor/D6656QzQ">5-HT receptors</a> (5-hydroxytryptamine, or <a href="/facts/Serotonin/EzY58q4a">serotonin</a> receptors) which are <a href="/facts/G-protein-coupled_receptor/0arUMkQc">G protein-coupled receptors</a>. This ion channel is <a href="/facts/Cation/wrbwhF3z">cation</a>-selective and mediates neuronal depolarization and excitation within the <a href="/facts/Central_nervous_system/k8I6To97">central</a> and <a href="/facts/Peripheral_nervous_system/KjVpVnHU">peripheral</a> <a href="/facts/Nervous_systems/CDxRKU2U">nervous systems</a>. </p><p>As with other ligand gated ion channels, the 5-HT3 receptor consists of five subunits arranged around a central ion conducting pore, which is permeable to <a href="/facts/Sodium/eYuSPu2V">sodium</a> (Na), <a href="/facts/Potassium/FWPwS7Rj">potassium</a> (K), and <a href="/facts/Calcium/hf252CC0">calcium</a> (Ca) ions. Binding of the <a href="/facts/Neurotransmitter/LlpYFSU3">neurotransmitter</a> 5-hydroxytryptamine (<a href="/facts/Serotonin/EzY58q4a">serotonin</a>) to the 5-HT3 receptor opens the channel, which, in turn, leads to an excitatory response in neurons. The rapidly activating, desensitizing, inward current is predominantly carried by <a href="/facts/Sodium/eYuSPu2V">sodium</a> and <a href="/facts/Potassium/FWPwS7Rj">potassium</a> ions. 5-HT3 receptors have a negligible permeability to <a href="/facts/Anions/wrbwhF3z">anions</a>. They are most closely related by homology to the <a href="/facts/Nicotinic_acetylcholine_receptor/k2s2pPHr">nicotinic acetylcholine receptor</a>. </p>