Background：

5-HT6， a Serotonin Receptor， appears to regulate cholinergic neurotransmission in the brain rather than the expected interaction as a modulator of dopaminergic transmission. This interaction predicts a possible role for 5-HT6 Receptor antagonists in the treatment of learning and memory disorders. The 5-HT6 Receptor is abundant in limbic areas， which participate in the control of mood and emotion. Some antidepressants and antipsychotics are potent 5-HT6 Receptor antagonists， making this gene valuable for the pharmaceutical industry. 5-HT6 may be involved in the pathogenesis of mood disorders， schizophrenia， in Alzheimer’s disease. A splice variant that has a 289bp deletion in the transmembrane region IV and the third intracellular loop has been isolated. 5-HT6 Receptor has been reported primarily in striatum of the brain. Expression has also been seen in stomach， spinal cord， and the lymphoid tissues of rats， including peripheral blood lymphocytes， spleen， and thymus. ESTs have been iso