Agonists are chemical substances that bind to and activate specific receptors in the body. These receptors are typically found on cell membranes and play a crucial role in regulating various biological processes and functions. Agonists work by mimicking the action of natural molecules or neurotransmitters that bind to the same receptors, thereby triggering a biological response. In the field of pharmacology, agonists are often used as drugs to treat a wide range of medical conditions by either enhancing or blocking the activity of certain receptors. For example, agonists of dopamine receptors are used to treat Parkinson's disease, while agonists of opioid receptors are commonly prescribed to manage pain. Overall, agonists play a critical role in understanding the mechanisms of receptor activation and developing therapeutic interventions for various diseases and disorders.