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. 2016 Jan 22;310(7):H873–H890. doi: 10.1152/ajpheart.00682.2015

Fig. 8.

Fig. 8.

The old myocardium presents blunted contractile response to β- adrenergic receptor (β-AR) stimulation. A: data for twitch properties in aging muscles in KHB and after exposure to isoproterenol (Iso; 100 nM) are shown as median and interquartile ranges (adult: n = 9 muscles, 7 dogs, 5.5 ± 0.5 yr; old: n = 10 muscles, 8 dogs, 13.0 ± 0.2 yr). *P < 0.01 vs. KHB. B: superimposed pseudo-ECGs obtained in the perfused adult LV myocardium in KHB and after exposure to the β-AR agonist Iso (100 nM). C: quantitative data for QT interval in adult and old LV myocardium in KHB and after exposure to Iso are shown as mean ± SE (adult: n = 4 muscles, 4 dogs, 6.9 ± 1 yr; old: n = 7 muscles, 5 dogs, 12.8 ± 0.3 yr). *P < 0.05 vs. KHB.