The precursor of cholesterol, (5-14C) mevalonate, was injected into the left cerebral ventricle of rats and the rats were killed at various time intervals afterwards. Brain slices were applied in close contact against Kodirex films to produce radioautographs. As chemical results had demonstrated, only radioactive cholesterol remained in the brain slices when radioautographs were prepared. Radioactive mevalonate had been discarded or metabolized. On the radioautographs prepared soon after injection, a high degree of blackening was observed in the areas close to the injection site, showing poor diffusion of the mevalonate. On all radioautographs, we could see a slight and homogeneous blackening, related to cholesterol synthesis, present in all the anatomical structures. Only the heavily myelinated structures near the injection site were more blackened, corresponding to a great density of cholesterol synthesis. Finally, changes in blackening distribution were observed with time. Radioautographs from rats killed 2.5 and 9 months after injection showed all the heavily myelinated structures very darkened. So, these radioautographs were similar to those obtained in the cholesterol transfer experiments. © 1969.
