Development of the Periventricular Nucleus as a Brain Center, Containing Dopaminergic Neurons and Neurons Expressing Individual Enzymes of Dopamine Synthesis

We have recently shown that the periventricular nucleus (PeVN) of adult rats is a mixed dopaminergic (DAergic) center containing three thousand neurons: DAergic neurons and those expressing one of the dopamine (DA)-synthesizing enzymes. This study aims to evaluate the development of the PeVN as a mixed DAergic center in rats in the perinatal period, critical for brain morphogenesis. During this period, the PeVN contains DAergic neurons and monoenzymatic neurons expressing individual enzymes of DA synthesis: tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC). In the perinatal period, the total number of such neurons triples, mainly due to monoenzymatic neurons; the content of L-DOPA, the end product of monoenzymatic TH neurons, doubles; and the content of DA, the end product of monoenzymatic AADC neurons and DAergic neurons, increases sixfold. Confocal microscopy has shown that, in the PeVN, all types of neurons and their processes are in close relationships, which suggests their mutual regulation by L-DOPA and DA. In addition, monoenzymatic and DAergic fibers are close to the third cerebral ventricle, located in the subependymal zone, between ependymal cells and in the supraependymal zone. These observations suggest that these fibers deliver L-DOPA and DA to the cerebrospinal fluid, participating in the neuroendocrine regulation of the brain.

Automated summary

This study evaluates the development of the periventricular nucleus (PeVN) as a mixed dopaminergic (DAergic) center in rats during the perinatal period. The PeVN contains dopamine-synthesizing neurons and mono-enzymatic neurons expressing tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC). The number of these neurons triples during the perinatal period, with a higher increase in mono-enzymatic neurons. The levels of L-DOPA, the end product of TH neurons, and dopamine, the end product of AADC neurons and DAergic neurons, also increase significantly. Confocal microscopy reveals close relationships between different types of neurons and their processes, suggesting their mutual regulation by L-DOPA and dopamine. These findings suggest the involvement of PeVN in the neuroendocrine regulation of the brain.