Atenolol

Atenolol is a selective β₁-adrenergic receptor blocker. It acts primarily on β₁ receptors in the heart, where it inhibits the stimulatory effects of epinephrine and norepinephrine on cardiac receptors. As a result, it reduces heart rate, myocardial contractility, and cardiac output, thereby lowering blood pressure and decreasing myocardial oxygen demand.

Atenolol also acts on β₁ receptors of the juxtaglomerular cells in the kidneys. By blocking these receptors, it decreases the release of renin, which in turn suppresses the renin-angiotensin-aldosterone system (RAAS). This reduces RAAS-mediated vasoconstriction and fluid retention signaling, thereby further contributing to the regulation of blood pressure.