What is the difference between an agonist and an antagonist?

An agonist is a substance that binds to a receptor in the body and activates it, leading to a biological response. This activation mimics the action of a natural messenger, such as a hormone or neurotransmitter, effectively enhancing or facilitating certain physiological processes. For example, morphine is an agonist for opioid receptors, producing pain relief by activating those receptors.

In contrast, an antagonist attaches to a receptor without activating it and, instead, blocks the receptor's function. This action inhibits the natural messenger from binding and prevents the biological response that would typically occur. An example of an antagonist is naloxone, which blocks opioid receptors and can reverse the effects of opioid overdose.

Understanding this distinction is crucial in pharmacology because it informs how different drugs can be used therapeutically to either enhance or inhibit bodily functions. Knowing the roles of agonists and antagonists helps healthcare professionals make informed decisions about treatment options based on the desired effects on specific receptors in the body.