Age-associated characteristics of vasomotor regulation of the pia mater arteries in rats.

The endothelium-dependent and myogenic reactions of pia mater arteries of the 1st-5th branching orders were studied in 1-, 3-, and 24-month-old rats by biomicroscopy method. The endothelium-independent (myogenic) reaction predominated in the 1st-3rd order branches and the endothelium-dependent vascular reaction in the 5th order branches of 3-month-old rats. Both regulatory mechanisms were equally developed in the 4th order branches. In 1-month-old rats, the endothelium-dependent reaction was more active in the majority of branches. In 24-month-old rats, this reaction was significantly higher than the endothelium-independent one only in the 4th and 5th order branches. In contrast to 3-month-old rats, the myogenic reaction of 24-month-old animals predominated in the 1st and 2nd order branches and the endothelium-dependent one in the 4th and 5th order branches. Vascular reactivity of 24-month-old rats was lower than in younger rats in all cases.