General Pharmacology

Beta-adrenoreceptors have been categorized into subclasses beta-1, beta-2, and beta-3. Beta-1 receptors are principally found in the heart. Stimulation of beta-1 receptors increases heart rate, cardiac contractility, and atrioventricular conduction rate. Beta-2 receptors are located in bronchial muscle, blood vessels, and the uterus. Stimulating beta-2 receptors causes dilation of bronchi and blood vessels. Beta-3 receptors, recently identified in mammals, are involved in the mediation of lipolysis. Available beta blockers have a low affinity for beta3 receptors.

Beta-adrenergic antagonists are competitive inhibitors at the beta-receptor site. They are classified as selective or nonselective based on relative affinity to the beta-1 and beta-2 receptors. The nonselective antagonists inhibit both beta-1 and beta-2 receptors, while the selective antagonists inhibit preferentially only one subtype of receptor. This selectivity is relative; at high concentrations, selective beta-adrenergic antagonists inhibit other beta receptors.

0 0

Post a comment