adrenoreceptor

Adrenoreceptors, also known as adrenergic receptors, are a class of G protein-coupled receptors that are targets of the catecholamines, adrenaline (epinephrine) and noradrenaline (norepinephrine). These receptors are found on the surface of many cells throughout the body and play a crucial role in the sympathetic nervous system's "fight or flight" response.

There are two main families of adrenoreceptors: alpha (α) and beta (β), each with further subtypes. Alpha-1 receptors are primarily found on smooth muscle, where their activation leads to vasoconstriction and increased peripheral resistance. Alpha-2 receptors are located presynaptically on nerve terminals and also in the central nervous system; their activation inhibits the release of noradrenaline, acting as a feedback mechanism. Beta-1 receptors are predominantly found in the heart, increasing heart rate and contractility. Beta-2 receptors are located in smooth muscle of the bronchioles and blood vessels, causing bronchodilation and vasodilation, respectively. Beta-3 receptors are mainly found in adipose tissue, where they stimulate lipolysis.

The activation of adrenoreceptors by adrenaline and noradrenaline triggers a cascade of intracellular events, ultimately leading to various physiological responses such as increased heart rate, blood pressure, respiration rate, and glucose metabolism. Drugs that target adrenoreceptors are widely used in medicine to treat conditions like hypertension, asthma, and heart failure.