DEVELOPMENT OF THE MESENCEPHALIC AND DIENCEPHALIC CATECHOLAMINE SYSTEMS IN HUMAN FETUSES - UPTAKE AND RELEASE OF CATECHOLAMINES IN-VITRO

Development of catecholamine (CA) systems of the ventral mesencephalon and diencephalon were studied in human fetuses at age 6, 8, 10 and 12 weeks, evaluating the CA specific uptake and K+-stimulated release wi th the isotopic biochemical technique. In the mesencephalon, the [H-3] dopamine (DA) uptake was detected as early as 6 weeks, suggesting the existence of either CA neurons or fibers. This was followed by gradual increase of the [H-3]DA uptake up to 10 weeks and-a subsequent fall a t 12 weeks. In the diencephalon, the uptake was first observed at 8 we eks, followed by its decrease at 10 weeks and subsequent increase at 1 2 weeks. The dynamic uptake is considered as a manifestation of the co ntinuous differentiation of CA neurons and sprouting of CA fibers. In contrast to uptake, no CA release was detected in response to membrane depolarization in the diencephalon and mesencephalon at any age studi ed, suggesting a timing dissociation between the onset of the CA uptak e and K+-provoked release in the course of neuron differentiation in h uman fetuses.