Agonists and antagonists are chemicals that produce specific physiological responses within cells. An agonist binds with or activates a receptor in the brain. An antagonist interacts with a receptor and blocks the receptor from accepting an agonist. Agonists and antagonists can be drugs or natural chemicals.
In other words, an agonist produces a response, and an antagonist prevents a response. Therefore, agonists increase the effects of neurotransmitters, while antagonists decrease the effects of neurotransmitters.
For example, an agonist will increase the excitatory effect if a neurotransmitter is excitatory. Conversely, an antagonist will decrease the excitatory action.
Agonists can be full agonists or partial agonists. Full agonists produce a “full” response from the associated receptor. Partial agonists only elicit a partial response.
For example, full pharmacological agonists include heroin and morphine. The drug buprenorphine is a partial agonist.
What Is a Receptor?
Agonists and antagonists interact with receptors. Receptors are proteins found on the membranes of brain cells. Receptors receive information from neurotransmitters, hormones, and neuropeptides. Then, they perform actions based on the type of instruction.
Different neurotransmitters bind with different receptors in the brain. For example, specific receptors interact with glutamate, the brain’s excitatory neurotransmitter. Other receptors bind with dopamine.