A. Overview Changes of B-adrenergic receptors B1-receptor down-regulation uncoupling of B1-adrenergic receptors increased activity of the inhibitory G protein(Gi) increased activity of G-protein receptor naseChanges of -adrenergic receptors – 1-receptor down-regulation – uncoupling of 1-adrenergic receptors – increased activity of the inhibitory G￾protein(Gi) – increased activity of G-protein receptor kinase A. Overview