Figure 2

Mechanisms of bronchodilatory action of antimuscarinic agents and beta2-adrenergic receptor agonists. Antimuscarinics block the binding of acetilcholine (ACh) to M3 muscarinic receptor, thereby inhibiting smooth muscle cell contraction. Beta2-adrenergic receptor agonists bind to beta2-adrenergic receptor and induce a cascade of signal transduction events that ultimately lead to smooth muscle relaxation.