Transient expression of 5-HT1A receptor binding sites in some areas of the rat CNS during postnatal development

The developmental evolution of 5-HT1A receptor binding sites was examined in the rat CNS during the early postnatal period using quantitative autoradiography and binding assays with 3H-8-OH-DPAT as the selective ligand. A progressive increase in the density of 5-HT1A sites was observed in the hippocampus, septum and cerebral cortex, up to adult levels which were reached around the third postnatal week. In contrast, complex biphasic (increase then decrease) changes were noted in other structures (for instance the nucleus of the lateral lemniscus), and even a progressive decrease in the density of 5-HT1A sites took place in the cerebellum during the first two postnatal weeks. The transient expression of 5-HT1A receptor binding sites in a structure such as the cerebellum which develops exclusively for the postnatal period further supports that 5-HT might play a trophic role during maturation of the CNS.