5-Hydroxytryptamine1A (5-HT1A) Receptor Responsivity in Anxiety Disorders and Depression

Based on radioligand binding studies, four pharmacologically distinct populations of 5-HT recognition sites located on neurons in the central nervous system have been designated 5-HT1, 5-HT2, 5-HT3 and 5-HT4. Moreover, current research indicates that 5-HT1 receptors comprise A, B, C, D and E subtypes (Glennon, 1990) and that the 5-HT2 receptor may be subdivided into two types (or possibly affinity states), while for the 5-HT3 binding site several subpopulations have been postulated, although no functional correlates such as second-messenger coupling, membrane effects and models for physiologic functions or behaviour have yet been identified for the 1E and 4 subtvpes.