Allosteric modulator

An allosteric modulator is a molecule that binds a receptor at a site separate from the main binding pocket and changes how strongly the receptor responds to its usual signal.

Most receptors have an orthosteric site, the pocket built for the body's own messenger, and one or more allosteric sites elsewhere on the protein. A molecule at an allosteric site does not switch the receptor on or off by itself; instead it adjusts the receptor's shape so that the natural signal produces a larger response, called positive modulation, or a smaller one, called negative modulation. Benzodiazepines, which enhance the GABA-A receptor, are a familiar example of positive allosteric modulation.

In cannabinoid pharmacology, CBD is often described in laboratory reports as a negative allosteric modulator of the CB1 receptor, meaning it may reduce how strongly THC or anandamide activate that receptor without blocking the site outright. This is one proposed explanation for why CBD does not produce intoxication, but the finding rests largely on cell-based experiments and its relevance in living people remains under investigation.