Maturation is associated with changes in rat cerebral artery structure, biomechanical properties and tone

Aim: This study evaluated the hypothesis that physiological maturation affects cerebral artery smooth muscle–endothelial interactions involved in pressure‐induced tone and alters the dimensional and biomechanical properties of small posterior cerebral arteries ( PCA ). Methods: Secondary branches of PCA from young (4–5 weeks old, n  = 11), adult (14–16 weeks old, n  = 11) and mature (44–47 weeks old, n  = 11) male S prague‐ D awley rats were isolated, cannulated, pressurized and subjected to a range of intraluminal pressures (10–110 mm Hg ) to determine tone with and without pharmacologic nitric oxide synthase ( NOS ) inhibition. Measurements of passive lumen diameter and wall thickness as a function of pressure were used to determine changes in structure, distensibility and wall stress; histological analysis was performed on vessel cross‐sections to assess collagen and elastin contents. Results: Although pressure‐dependent tone decreased significantly during ageing, differences between groups were abolished by NOS inhibition. Vessel diameters increased in adult vs. young rats (at 90 mmHg, 233 ± 6.0 μm vs. 192 ± 4.5 μm; P  < 0.05), possibly secondary to somatic growth. Further ageing was associated with reductions in lumen diameter (207 ± 6.5 μm; P  < 0.05), increased wall and media thickness (and wall/lumen ratio) and cross‐sectional area. Distensibility and wall collagen were unchanged, although elastin content was significantly reduced. Conclusions: Maturation is associated with differences in PCA dimensional properties that indicate a pattern of initial outward eutrophic, followed by inward hypertrophic remodelling. Functionally, the contribution of basal NO increases with age in a way that reduces pressure‐dependent tone and diminishes vasodilator reserve.