Agonistinduced

Agonist-induced refers to effects that arise from the activation of a receptor by an agonist. In pharmacology, an agonist is a molecule that binds to a receptor and stabilizes an active conformation, triggering a cellular response.

Typically, agonist binding initiates signal transduction through the receptor, such as G protein activation, second messenger production, or kinase cascades, leading to physiological changes in cells and tissues. The overall response depends on the agonist’s potency and efficacy, the density of receptors, and the efficiency of downstream signaling. Potency describes the concentration needed to achieve a given effect, while efficacy describes the maximal response attainable by the agonist.

Two related phenomena influence agonist-induced responses over time. Desensitization, or tachyphylaxis, is a reduced response to a receptor despite ongoing presence of the agonist, often due to receptor phosphorylation and recruitment of arrestin, which uncouples signaling or promotes receptor internalization. Downregulation can occur with chronic agonist exposure, resulting in fewer receptors on the cell surface and a diminished ability to respond.

Examples include morphine activating mu-opioid receptors to produce analgesia, or epinephrine activating beta-adrenergic receptors to increase heart rate. In research and medicine, understanding agonist-induced signaling helps explain drug efficacy, tolerance, withdrawal, and the potential for drug interactions.

See also: agonist, receptor, desensitization, tachyphylaxis, downregulation.