[Studies of age-related changes in intracerebral small vessels of rat--do all cerebral blood vessels get aging concurrently?].

Age-related changes of intracerebral small blood vessels were studied with light and electron microscopes. In the first step of this investigation (Experiment 1), Wistar rats of 4-month-old were employed to determine the appropriate concentration of administrated HRP (horseradish peroxidase) for surveying the uptake capacity of HRP. Each rat was injected HRP intravenously under light anesthesia with ether. After 30 minutes, rat brains were excised and prepared for stretch specimen (Mato et al, 1979). Light microscopically, corresponding with decrease of the concentration of injected HRP, the reaction products of HRP in the cytoplasm of fluorescent granular perithelial (FGP) cells reduced linearly and the injection of 5 mg HRP revealed only FGP cells in the parietotemporal region of cerebral cortex. Referring to the results mentioned above, 10 mg of HRP was decided to be applicable dose for the following study. In the next experiment (Experiment 2), Wistar rats of 4-month-old, 1.7-year-old and 2.4-year-old were used for the study on the relation between morphological alteration of vascular cells and changes of uptake capacity of FGP cells in aging. At 30 minutes after the injection of 10 mg, rats were perfused and fixed with 2.5% glutaraldehyde and 2% paraformaldehyde under light anesthesia. Then, rat brains were removed and divided coronally into three parts. After slicing with Vibratome, number and distribution of FGP cells were studied under light microscope. The other specimens were dehydrated and embedded in Epon 812. The ultrastructure of vascular cells (endothelial and smooth muscle cells) and FGP cells at each age was examined with JEM 2000 EX electron microscope. Supplementary, ultrastructure of middle cerebral and retinal arteries of 2.4-year-old rats was also studied for comparison with that of the intracerebral (cortical)small vessels. The findings obtained from Experiment 2 could be summarized as follows; 1. Light microscopically, in 4-month-old and 1.7-year-old rats, FGP cells including positive granules of HRP were often recognizable along small blood vessels of cerebrum, especially in cerebral cortices. In 2.4-year-old rats, the numbers of FGP cells with positive granules of HRP decreased significantly (p less than 0.01). It was confirmed that the uptake capacity of FGP cells reduced with aging. But, exceptionally, regardless from aging of animals, FGP cells belonging to a few special vessels in the parietotemporal area of cerebral cortices included many and intense reaction products. 2. Electronmicroscopically, the vascular cells changed in appearance and contents with aging.(ABSTRACT TRUNCATED AT 400 WORDS)