Human 5-HT6 receptors are G protein-coupled receptors. The cDNA encodes a 440-amino-acid polypeptide. The 5-HT6 receptors are expressed exclusively in brain regions such as striatum, cortex, nucleus accumbens, olfactory tubercle, hippocampus, hypothalamus, amygdala and cerebellum. The 5-HT6 receptors appear to regulate GABAergic, glutamatergic and cholinergic neurotransmission and are involved in the regulation of cognition, feeding and sleep/wake regulation. They may also play a role in mediating the effects of some antipsychotic agents, and in modulating sensory gating which is often affected in schizophrenic patients.