5-Hydroxytryptamine (5-HT, also commonly known as serotonin) is synthesized in enterochromaffin cells in the intestine and in serotonergic nerve terminals. In the periphery, 5-HT mediates gastrointestinal motility, platelet aggregation, and contraction of blood vessels. Many functions of the central nervous system are influenced by 5-HT, including sleep, motor activity, sensory perception, arousal, and appetite. A family of 12 GPCRs and one ion channel mediate the biological effects of 5-HT (Hoyer et al., 1994). 5-HT2C is expressed in the brain and spinal cord, especially the choroid plexus. 5-HT2C receptor agonists may have important clinical value in the trea™ent of mental and eating disorders, such as depression, panic anxiety, OCD, bulimia, and obesity. GenScript's cloned human 5-HT2C-expressing cell line is generated in the CHO-K1 host.