The serotonin 5-HT₇ receptors: two decades of research

Like most neurotransmitters, serotonin possesses a simple structure. However, the pharmacological consequences are more complex and diverse. Serotonin is involved in numerous functions in the human body including the control of appetite, sleep, memory and learning, temperature regulation, mood, behavior, cardiovascular function, muscle contraction, endocrine regulation, and depression. Low levels of serotonin may be associated with several disorders, namely increase in aggressive and angry behaviors, clinical depression, Parkinson’s disease, obsessive–compulsive disorder, eating disorders, migraine, irritable bowel syndrome, tinnitus, and bipolar disease. These effects are mediated via different serotonin (5-HT) receptors. In this review, we will focus on the last discovered member of this serotonin receptor family, the 5-HT₇ receptor. This receptor belongs to the G protein-coupled receptor superfamily and was cloned two decades ago. Later, different splice variants were described but no major functional differences have been described so far. All 5-HT₇ receptor variants are coupled to Gα_s proteins and stimulate cAMP formation. Recently, several interacting proteins have been reported, which can influence receptor signaling and trafficking.