Central serotonergic receptors: evidence for heterogeneity and characterization by ligand-binding

Evidence has accumulated which suggests that receptors for serotonin exist in multiple forms both in the central nervous system and the periphery. This has come from the use of a variety of techniques and a number of different tissues. In the central nervous system the ligand-binding technique has proven particularly useful for characterizing different types of serotonin receptors, and two major classes of central serotonin receptors have been proposed on the basis of studies using this procedure. The first group (5-HT1 receptors) is defined by the high-affinity binding of 3H-serotonin in the brain, and the second (5-HT2 receptors) is defined by the high-affinity binding of 3H-spiperone in the frontal cortex. The 5-HT1 sites have themselves been shown to be a heterogeneous group, and recent studies suggest that it is possible to synthesize tryptamine analogues which can discriminate between the different types of 5-HT1 receptors. Such studies suggest the possibility of designing new selective serotonin agonists and antagonists for the study of the effects of specific receptor subtypes on behavioral and physiological activities.