5HT3Rezeptors

5-HT3 receptors (5-HT3R) are a class of serotonin receptors that function as ligand-gated ion channels. They belong to the Cys-loop receptor superfamily and form pentameric complexes that gate cations, typically Na+, K+, and Ca2+. Activation by serotonin (5-hydroxytryptamine) produces fast excitatory postsynaptic responses and can influence neurotransmitter release in connected neurons.

In humans, the receptor is primarily formed by 5-HT3A subunits, which can assemble with 5-HT3B subunits to produce heteromeric receptors with distinct pharmacology. Additional subunits, named 5-HT3C, 5-HT3D and 5-HT3E, have been described and may modify receptor properties or contribute to tissue-specific subtypes, though they do not form functional homomeric channels on their own in many contexts.

5-HT3 receptors are widely distributed in both the central and peripheral nervous systems, with notable presence in the enteric nervous system and regions such as the area postrema and nucleus of the solitary tract in the brain. They modulate visceral sensation, gut motility and secretion, and play a role in the vomiting reflex, nausea, anxiety-related processes, and pain modulation through rapid excitatory signaling and modulation of other neurotransmitter systems.

Clinically, 5-HT3 receptors are targeted by antagonists used as antiemetics, including ondansetron, granisetron, tropisetron and palonosetron, effective against chemotherapy- and postoperative-induced nausea. In some conditions such as IBS-D, selective 5-HT3 antagonists like alosetron are used with restricted indications due to potential adverse effects, including constipation and, rarely, ischemic events.