Figure 3.

Schematic representation of β-adrenergic signaling in cardiomyocytes. Sympathetic stimulation and the consequent neurotransmitter release initiates the β-adrenergic signaling cascade in cardiomyocytes. Agonist binding to the β-adrenergic receptor (β-ADR) activates, via G_s, the plasma membrane bound adenylate cyclase (AC), which catalyzes the conversion of ATP to cAMP. cAMP activates I_f and PKA. PKA modulates, via phosphorylation, a number of cellular substrates, including ion channels, transporters, exchangers, intracellular Ca²⁺-handling proteins, and the contractile machinery.