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An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
Agonist vs. antagonist. In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, behaves as an antagonist (a substance that binds to a receptor but does not activate and can block the activity of other agonists).
Receptors bind with endogenous ligands to produce a physiological effect and regulate the body and cellular homeostasis. In a ligand-receptor interaction, the ligand binds with the receptors to form a drug-receptor complex, producing a biological response. [3] [4] The biological nature of receptors can be enzymes, nucleic acids or cellular ...
Physiological antagonism describes the behavior of a substance that produces effects counteracting those of another substance (a result similar to that produced by an antagonist blocking the action of an agonist at the same receptor) using a mechanism that does not involve binding to the same receptor.
Receptor theory is the application of receptor models to explain drug behavior. [1] Pharmacological receptor models preceded accurate knowledge of receptors by many years. [2] John Newport Langley and Paul Ehrlich introduced the concept that receptors can mediate drug action at the beginning of the 20th century.
The action of drugs on the human body (or any other organism's body) is called pharmacodynamics, and the body's response to drugs is called pharmacokinetics. The drugs that enter an individual tend to stimulate certain receptors, ion channels, act on enzymes or transport proteins. As a result, they cause the human body to react in a specific way.
“The brain changes, and it doesn’t recover when you just stop the drug because the brain has been actually changed,” Kreek explained. “The brain may get OK with time in some persons. But it’s hard to find a person who has completely normal brain function after a long cycle of opiate addiction, not without specific medication treatment.”
This GABA A receptor contains many binding sites that allow conformational changes and are the primary target for drug development. The most common of these binding sites, benzodiazepine, allows for both agonist and antagonist effects on the receptor. A common drug, diazepam, acts as an allosteric enhancer at this binding site. [5]