What is the mechanism of action of beta agonists?

Beta agonists work by stimulating adenylate cyclase, which in turn increases the production of cyclic AMP (cAMP). This increase in cAMP activates protein kinase A (PKA), leading to a series of downstream effects that cause smooth muscle relaxation, particularly in the airways and vascular smooth muscle. This mechanism is crucial in the therapeutic use of beta agonists for conditions like asthma and chronic obstructive pulmonary disease (COPD), where bronchodilation is needed.

cAMP serves as a secondary messenger in many signaling pathways, including those activated by beta-adrenergic receptors. The binding of a beta agonist to its receptor activates G-proteins that stimulate adenylate cyclase, resulting in higher levels of cAMP within the cell. This promotes relaxation of smooth muscle and inhibits the release of inflammatory mediators, providing relief from bronchospasm.

The other options describe mechanisms that are not associated with the action of beta agonists. For example, inhibiting adenylate cyclase would lead to decreased cAMP levels, opposing the effects of beta agonists. Blocking calcium channels and increasing intracellular calcium concentration pertain more to the actions of different classes of medications, such as calcium channel blockers, rather than the action of beta agonists