Serotonin, which also named as 5-hydroxytryptamine (5-HT), is a neurotransmitter, which plays significant roles in a wide range of physiological and pathological processes. Depression is a complex disease that involves numerous factors, increasing evidences have showed that the level of 5-HT was lower in depressed patients and the administration of some selective serotonin re-uptake inhibitors exhibited antidepressant effects. The 5-HT1A receptor is a key protein in the brain serotonin system, modulating the release of 5-HT and other neurotransmitters. Behavioral and molecular biological studies have demonstrated that the differences of 5-HT1A receptor regulation was connected with depression and the responses to antidepressants. In this review, the authors will introduce the structure and function of 5-HT1A receptor and summarize some antidepressants targeting 5-HT1A receptor, including 5-HT1A receptor agonists and antagonists in a clinic, active ingredients of traditional Chinese medicine. And we found the major of drugs by targeting 5-HT1A receptor on the market or in clinical trials mostly have the similar functional groups, such as piperazine, piperidine, and pyrimidine. There are also some literatures found that these functional groups may be the site produce activity. So, we hope that it may provide basis and references for the research of the clinical drugs for depression.

Serotonergic dysfunction is thought to contribute to the pathophysiology of schizophrenia but the evidence has not been systematically synthesised before. We therefore systematically reviewed postmortem and in vivo molecular imaging studies of serotonin function in schizophrenia. We identified fifty relevant studies investigating eight different serotonin receptor systems in a total of 684 patients and 675 controls. Meta-analysis of postmortem studies found an elevation in prefrontal 5-HT1A receptors with a moderate to large effect size (N=8, 85 patients and 94 controls, SMD=0.60; CI: 0.17-1.03; p=0.007) and a reduction with a large effect size in prefrontal 5-HT2A receptors (N=8, 168 patients and 163 controls, SMD=-0.73; CI: -1.33, -0.12; p=0.019) in schizophrenia vs healthy controls. The evidence for alterations in serotonin transporter availability or other serotonin receptors (5-HT1B; 5-HT1D; 5-HT3; 5-HT4; 5-HT7) is limited. There are fewer studies investigating 5-HT receptors in schizophrenia with neuroimaging. Findings indicated possible 5-HT alterations at psychosis onset, although due to the limited number it was not possible to combine studies in a meta-analysis. Further in vivo studies, particularly in drug naive patients using radiotracers that can index high affinity states, will help determine if the postmortem findings are primary or secondary to other factors.