Characterization and localization of serotonin receptors in human brain postmortem

Saturation binding experiments, quantitative autoradiography and computerized densitometric techniques were used to study serotonin S1 and S2 receptor distribution in the human brain, using [3H]serotonin and [3H]ketanserin, respectively. The two ligands exhibited saturable binding to sites very similar in affinity and pharmacology to the S1 and S2 receptors in rat brain. The highest densities of S1 receptors appeared over the hippocampus and layer I of the cortex. S2 receptors were highest in layer IV of the cortex. Analysis of ligand binding to coronal sections through a whole hemisphere allows quantification of receptors in very discrete regions--such as the individual layers of the cortex--and has the advantage of simultaneous visualization of receptors in many different regions which are represented on a single section. Gross similarities but also important differences are found between serotonin receptor distribution in rat and human, stressing the importance of performing these kind of experiments on human brains if they are to be used for the study of diseases and drug action in human subjects.