What is the Difference Between Agonist and Antagonist?

The main difference between agonists and antagonists lies in their interaction with receptors and the responses they produce:

• Agonist: An agonist is a molecule that binds to and activates a target, typically a metabotropic or ionotropic receptor, mimicking the actions of a neurotransmitter or hormone and producing a similar response. For example, opioid agonists like morphine and heroin bind to opioid receptors and produce responses such as "liking," analgesia, and respiratory depression.
• Antagonist: An antagonist is a molecule that binds to a target (e.g., a receptor) and prevents other molecules, such as agonists, from binding, without activating the receptor. Antagonists do not produce a response on their own but block or oppose the natural action or response of a receptor. For example, naltrexone is an opioid receptor antagonist that binds to opioid receptors without activating them, preventing the receptors from being activated by agonists like heroin or morphine.

In summary:

• Agonists mimic the actions of neurotransmitters or hormones and produce a response when they bind to receptors.
• Antagonists bind to receptors without activating them, preventing other molecules from binding and blocking the receptor's natural response.

Comparative Table: Agonist vs Antagonist

Here is a table that compares the differences between agonists and antagonists:

Agonists are substances that activate receptors to produce a biological response, mimicking or enhancing the action of a natural neurotransmitter or hormone. Antagonists, on the other hand, bind to receptors but do not activate them, blocking the action of the natural neurotransmitter or hormone. In summary, agonists create a certain action, while antagonists oppose a certain action.