Agonists are defined as drugs that:

• A. Block receptor activity
• B. Bind to and stimulate tissue receptors
• C. Have no effect on receptors
• D. Only bind without triggering a response

Answer: (B)

Agonists are defined as drugs that bind to and stimulate tissue receptors. This means that when an agonist attaches to a receptor, it activates the receptor and triggers a biological response. This is particularly important in pharmacology, as agonists are often used to replicate or enhance the actions of naturally occurring substances in the body, leading to therapeutic effects.

For example, in the context of anesthesia, an agonist might stimulate pain relief or sedation through its action at specific receptor sites. This class of drugs plays a crucial role in various treatment protocols by mimicking the action of endogenous ligands or neurotransmitters. The binding and stimulation of the receptor by an agonist result in a physiological response that can be beneficial in managing certain medical conditions.