Effect of age on blood vessels and neurovascular appositions in the CA1 region of the rat hippocampus.

Rats aged 3, 9, 24 and 30 months were used in this study. Increased basal lamina thickening in capillaries, muscular large vessels and nonmuscular large vessels was shown with advancing age. There is also an age-related increase in the area of mitochondria in smooth muscle cells. These ultrastructural changes may underlie observed age-related functional changes in the vasculature. They may be a compensatory response of the vessel wall cells to a declining capacity to handle the continual and varying shear stress exerted by the blood. Ultrastructural differences between capillaries and the two types of large vessels are reported and discussed in terms of their functional significance. It was noted that there are more dendrites adjacent to capillaries than to large vessels, however, this was unaffected by increasing age. Since advancing age did not alter the number of neuronal processes adjacent to vessels, age-related compromises in vessel function may not be subjected to neuronal regulation.