| Abstract: | The distribution of 3H-serotonin-binding structures in hypothalamus of 16 and 18 day old fetuses and of 9 day old rats was studied after intraventricular injection of 3H-serotonin. Rare 3H-serotonin-binding little differentiated cells were found predominantly in the intermediate zone of the 3rd ventricle in the retrochiasmatic area wall on the 16th and 18th days of prenatal development. In addition, an aggregate of heavily labeled neurones was observed in the suprachiasmatic area. At the same time 3H-serotonin-binding fibers first appeared, predominantly in the optic chiasma and perichiasmatic area. Radioactively labelled cells, which can be characterized by their morphology as differentiated neurones, were located in the dorsomedial nucleus on the 9th day of postnatal development. The number of serotonin-binding fibers markedly increased but the pattern of their distribution was, on the whole, similar to that in fetuses. The data obtained suggest that the main stages of structural organization of serotoninergic system of hypothalamus in rats are realized during perinatal period. |
