A chemical that binds to a receptor and increases its activity.
A chemical that binds to a receptor and increases its activity. Agonists are classified by the way they interact with their receptor. There are direct (orthosteric) agonists, indirect (allosteric) agonists, and biased agonists, for example.
Summary from Wikipedia:
An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response. Whereas an agonist causes an action, an antagonist blocks the action of the agonist, and an inverse agonist causes an action opposite to that of the agonist.