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Aging‐induced changes in angiotensin II‐induced contractions and tachyphylaxis of isolated carotid arteries

Angiotensin II (Ang II) is a potent vasoconstrictor, yet the potential aging‐ induced changes in the magnitude of responses have not yet been explored. We hypothesized that aging induces changes in the magnitude of vasomotor responses to Ang II. Thus carotid arteries from newborn (8 days: 8d), young (2 months: 2m) and old (24 months: 24m) rats were isolated and placed in a wire myograph to measure changes in their isometric tension. Two dose response curves to Ang II were obtained in a sequential manner (1‐, and 2‐administration (Adm). Contractions of vessels to 1‐Adm of Ang II in 8d vessels were significantly less compared to those of 2m and 24m, which were similar in magnitude (1.40±0.2 mN and 5.2±0.6 and 5.7±0.39 mN, respectively). Compared to the 1‐Adm, contractions of vessels to 2‐Adm of Ang II were significantly reduced in 2m and 24m vessels (4.4±0.54 and 0.5±0.19mN), whereas it did not change in vessels of 8d rats (1.28±0,2 mN).