Käänteisagonismi

Käänteisagonismi, often translated as anti-agonism or inverse agonism, is a concept in pharmacology describing a type of receptor modulation. While an agonist binds to a receptor and elicits a biological response, and an antagonist binds to a receptor but blocks the action of agonists, an inverse agonist binds to the same receptor as an agonist but produces the opposite effect. This implies that many receptors possess a basal level of activity even in the absence of an agonist.

The existence of basal receptor activity is a prerequisite for inverse agonism. If a receptor has no activity without a ligand, an antagonist that simply blocks binding would be indistinguishable from an inverse agonist. Inverse agonists effectively reduce this constitutive activity. This phenomenon has been observed for various receptor systems, including G protein-coupled receptors (GPCRs) like histamine receptors and cannabinoid receptors.

Understanding inverse agonism has significant implications for drug development. It suggests that therapies could be designed not only to block unwanted receptor activation but also to actively suppress existing receptor signaling. This opens new avenues for treating conditions where a receptor's basal activity is implicated in disease pathology. For example, inverse agonists for certain neurotransmitter receptors might be useful in treating anxiety or sleep disorders.