FIGURE 4.

Natriuretic peptide receptor (NPR) (A) and adenosine (B) receptor signaling cascade in a sinoatrial node myocyte. A₁R, adenosine receptor 1; AC, adenylyl cyclase; ANP, atrial natriuretic peptide; BNP, brain natriuretic peptide; cAMP, cyclic adenosine monophosphate; cGMP, cyclic guanosine monophosphate; CNP, C-type natriuretic peptide; DAG, diacylglycerol; DNP, Dendroaspis natriuretic peptide; GC, guanylyl cyclase; I_CaL, long-lasting (L-type) Ca²⁺ current; I_f, “funny” current; I_KAdo, adenosine-induced inwardly rectifying K+ current; I_Ks, slow delayed rectifier K⁺ current; I_NCX, Na⁺-Ca²⁺ exchanger current; IP₃, inositol triphosphate; IP₃R, inositol triphosphate receptor; P, phosphorylation; PDE, phosphodiesterase; PIP₂, Phosphatidylinositol 4,5-bisphosphate; PKA, phosphokinase A; PKC, phosphokinase C; PKG, phosphokinase G; PLB, phospholamban; PLC, phospholipase C; RyR, ryanodine receptor, SERCA, sarco/endoplasmic reticulum Ca²⁺-ATPase; SR, sarcoplasmic reticulum.