A receptor antagonist is a type of molecule that binds to a specific receptor in the body but does not activate it. Instead, it blocks or inhibits the action of other substances, such as hormones or neurotransmitters, that would normally bind to that receptor. This can help regulate various physiological processes and is often used in medical treatments. Receptor antagonists are important in pharmacology and are commonly used in medications for conditions like high blood pressure, anxiety, and allergies. By preventing the activation of certain receptors, these drugs can help alleviate symptoms and improve health outcomes for patients.