Serotonin through pregnancy. Comparative researches in different species and in mankind.

By spectrofluorimetric method there was followed the blood and cerebral serotonin content in different species of mammalians: in 28 women, from the venous whole blood collected by cubital puncture, and in 20 cows, from the jugular whole blood. In 90 female rats the serotonin content from hypothalamus, rhinencephalon, mesencephalon, and sensorimotor cortex was determined. The obtained data show that in the course of labour in both species the blood serotonin concentration is decreased, returning to its initial values after delivery. The serotonin concentration in cows is 10--15 times higher than in women. As concerns the serotonin values in the cerebral nuclei through pregnancy, a progressive and significant increase of its content was noted in the hypothalamus, rhinencephalon, and mesencephalon, but not in the cerebral cortex. It reaches its maximum concentration at the end of pregnancy. It was concluded that during pregnancy a reduction of serotonin release processes is produced, which can signify a lower functional level of the serotoninergic structures implied in the regulation of the reproductive functions. The data are interpreted in the light of the particular endocrine state existing through pregnancy, attributing to serotonin a role in the functioning of PIF-prolactin system.