In contrast to the “heart failure” conditions, the decrease in available β1-AR concentration shifts both NE− and NE+ β-nullclines to the left (Fig. 5, compare B and D), while the inhibition of GRK2 shifts the NE+ β-nullcline to the right, closer to the NE- β nullcline (Fig. 5, D–F). Here, ADRB1 is linked to heart failure.