Dobutamine and tyramine stimulation of cardiac function. Black bars are WT, grey bars are KO mice. A, B) The beta agonist dobutamine stimulates dP/dtMAX to similar extent in both genotype 3 days (A) and 7 days (B) after surgery. dP/dtMAX is decreased compared to sham in both genotypes 3 days after MI, but is decreased only in WT mice 7 days after MI. Mean±SEM, n=5–6, * p<0.05. C, D) Tyramine induced NE release stimulates dP/dtMAX to similar extent in both genotype 3 days (C) and 7 days (D) after surgery. dP/dtMAX is decreased significantly after MI only in WT mice. Mean±SEM, n=5–6, ** p<0.01.