Autoradiographic study of nucleic acid precursor incorporation in nerve cells of the mouse brain

Following intravenous administration of five tritiated nucleic acid bases and five nucleosides in mice the intensity of labelling of the cerebral cortex cells and the liver cells show the following pattern. Cytidine and uridine cause intense labelling; uracil, adenine, adenosine, guanosine, guanine, thymine and cytosine only a weak labelling. The choroid plexus is labelled intensely by cytidine and uridine, moderately by guanosine and adenosine, weakly by other substances.In vitro experiments and intracerebral injection with uridine, uracil, adenine and adenosine give the same labelling pattern as intravenous injection. Inhalation of CO₂ does not alter the labelling of nerve cells apart from that due to the uridine group, where a weaker labelling of the nerve cells is observed.It is concluded that, in the case of the nucleic acid precursors used here, metabolic specificities are of greater significance for the labelling pattern of the nerve cells than the transport specificities of the blood-brain barrier.