The brain is one of the sources of L-dihydroxyphenylalanine in systemic circulation in fetuses and neonatal rats

Non-dopaminergic neurons partly expressing dopaminergic phenotype: Distribution in the brain, development and functional significance

“…In addition to monoenzymatic AADC neurons, the glial cells and endothelial cells of blood vessels possess enzymatically active AADC (Hardebo et al, 1980;Juorio et al, 1993). These cells are probably capable of synthesizing DA from L-DOPA derived either from the monoenzymatic TH neurons, or coming from general circulation (Melnikova et al, 2006). DA synthesis from L-DOPA in TH-lacking but AADC-expressing cells might also be a compensatory reaction serving to increase local DA synthesis from circulating L-DOPA under a failure of DA-ergic neurons.…”

“…A number of other monoenzymatic AADC neurons were also suggested to co-express neuropeptides that is indirectly supported by an overlapping in the distribution of monoenzymatic AADC neurons and the enkephalin-producing neurons in the lateral parabrachial nucleus (D3), as well as the substance P-and neurotensin-producing neurons in the nucleus of the solitary tract (D2) (Jaeger et al, 1984). From the fact that the monoenzymatic AADC neurons are in close topographic relations with cerebral blood vessels (Ugrumov et al, 1989a), it indirectly follows that these neurons may synthesize DA and serotonin from L-DOPA and 5,7-hydroxytryptophan circulating in blood (Karasawa et al, 1994;Melnikova et al, 2006).…”