Fig. 1.

Myogenic tone in PCAs isolated from young and aged Fischer 344 rats. Intraluminal pressure was increased from 20 to 200 mmHg in young (n = 10) and aged (n = 9) rat PCAs incubated in 2.8 mM CaCl₂ or 0 mM CaCl₂ with 4 mM EGTA. Vessel diameter was recorded at each pressure point over a period of 50 min. a Young vessel diameter measured with increased pressures in 2.8 mM CaCl₂. b Young vessel diameter measured with increased pressures in 0 mM CaCl₂. c Aged vessel diameter measured with increased pressures in 2.8 mM CaCl₂. d Aged vessel diameter measured with increased pressures in 0 mM CaCl₂. e Integrated information on pressure and diameter from young and aged vessels that were monitored in the presence and absence of 2.8 mM CaCl₂. f Myogenic tone for young and old vessels. Tone was calculated as the difference in diameter in the presence and absence of calcium, as a fraction of the diameter in the absence of calcium. * P < 0.05 for young vs. aged animals at each pressure point. Significance was determined using repeated unpaired t tests with Holm-Sidak correction for multiple comparisons at each pressure point