Käänteisagonismin

Käänteisagonismi, often translated as "reverse agonism," is a concept in pharmacology describing a type of receptor ligand. Unlike agonists, which activate a receptor to produce a biological response, or antagonists, which block receptor activation, reverse agonists bind to a receptor and induce a pharmacological response opposite to that of the receptor's endogenous agonist. This means that even in the absence of the natural signaling molecule, a reverse agonist can cause the receptor to adopt an inactive state, thereby reducing the baseline activity of the receptor.

This phenomenon is particularly relevant for receptors that exhibit constitutive activity, meaning they are active to some degree even without any ligand bound. In such cases, a neutral antagonist would simply block this constitutive activity, bringing the receptor to a basal, inactive state. A reverse agonist, however, would actively drive the receptor to a state of even lower activity than the basal level. The degree of reverse agonism can vary, with some ligands being more potent in reducing receptor activity than others.

The discovery and understanding of reverse agonism have expanded the therapeutic possibilities for various conditions. For example, in the treatment of anxiety disorders, drugs that act as inverse agonists at certain benzodiazepine receptors can reduce the tonic activity of these receptors, leading to a calming effect. Similarly, reverse agonism has been explored in areas like histamine receptors and opioid receptors, offering new avenues for drug development by manipulating receptor activity in a more nuanced way than simple activation or blocking.