Quantitative evaluation of the blood-brain barrier capacity to form dopamine from circulating L-DOPA.
The ability of the blood-brain barrier to form dopamine from increasing doses of systemically administered L-DOPA has been studied in rats by a combination of chemical determination of dopamine, and histochemical and cytofluorometric measurements of L-DOPA and dopamine. The break-through of L-DOPA from the circulation into the brain parenchyma via the enzymatic blood-brain barrier was estimated by comparing the amount of newly formed dopamine in the caudate nucleus-putamen and in the cerebellum. The capillaries were found to efficiently trap L-DOPA in their walls, and an upper limit was reached (at an administered i.p. dose of 100 mg/kg of L-DOPA). It could be estimated that approximately 3% of the total dose of L-DOPA given was decarboxylated by the blood-brain barrier. The possible influence by the regional differences in perfusion of the two regions seen after administration of L-DOPA was ruled out in measurements of local cerebral blood flow using the 14C-ethanol technique.
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002196:Capillaries / Q000187:drug effects; D002421:Caudate Nucleus / Q000378:metabolism; D002531:Cerebellum / Q000098:blood supply / Q000378:metabolism; D003342:Corpus Striatum / Q000098:blood supply / Q000378:metabolism; D004298:Dopamine / Q000096:biosynthesis*; D005260:Female; D006651:Histocytochemistry; D007980:Levodopa / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009526:Nialamide / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology
D007980:Levodopa; D012110:Reserpine; D009526:Nialamide; D004298:Dopamine