{{DISPLAYTITLE:5-HT2C receptor}} The 5-HT2C receptor is a subtype of 5-HT receptor that binds the endogenous neurotransmitter serotonin (5-hydroxytryptamine, 5-HT). It is a G protein-coupled receptor (GPCR) that is coupled to Gq/G11 and mediates excitatory neurotransmission. HTR2C denotes the human gene encoding for the receptor, that in humans is located at the X chromosome. As males have one copy of the gene and in females one of the two copies of the gene is repressed, polymorphisms at this receptor can affect the two sexes to differing extent. Structure At the cell surface the receptor exists as a homodimer. The crystal structure has been known since 2018. Distribution 5-HT2C receptors are located mainly in the choroid plexus, and in rats is also found in many other brain regions in high concentrations, including parts of the hippocampus, anterior olfactory nucleus, substantia nigra, several brainstem nuclei, amygdala, subthalamic nucleus and lateral habenula. 5-HT2C receptors are also found on epithelial cells lining the ventricles. Function The 5-HT2C receptor is one of the many binding sites for serotonin. Activation of this receptor by serotonin inhibits dopamine and norepinephrine release in certain areas of the brain. 5-HT2C receptors are claimed to significantly regulate mood, anxiety, feeding, and reproductive behavior. 5-HT2C receptors regulate dopamine release in the striatum, prefrontal cortex, nucleus accumbens, hippocampus, hypothalamus, and amygdala, among others. Research indicates that some suicide victims have an abnormally high number of 5-HT2C receptors in the prefrontal cortex. Agomelatine, which is a 5-HT2C and 5-HT2B antagonist as well as a MT1 and MT2 agonist, is an effective antidepressant. It has been called a norepinephrine-dopamine disinhibitor because antagonism of 5-HT2C receptors by agomelatine results in an increase of dopamine and norepinephrine activity in the frontal cortex. Conversely, many SSRIs (but not fluoxetine, which is a 5-HT2C antagonist) indirectly stimulate 5-HT2C activity by increasing levels of serotonin in the synapse although the delayed mood elevation that is usually typical of SSRIs is usually paralleled by the downregulation of the 5-HT2C receptors. Many atypical antipsychotics block 5-HT2C receptors, but their clinical use is limited by multiple undesirable actions on various neurotransmitters and receptors. Fluoxetine acts as a direct 5-HT2C antagonist in addition to inhibiting serotonin reuptake, however, the clinical significance of this action is variable. Several tetracyclic antidepressants, including mirtazapine, are potent 5-HT2C antagonists; this action may contribute to their efficacy. An overactivity of 5-HT2C receptors may contribute to depressive and anxiety symptoms