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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).
A co-agonist works with other co-agonists to produce the desired effect together. NMDA receptor activation requires the binding of both glutamate, glycine and D-serine co-agonists. Calcium can also act as a co-agonist at the IP3 receptor. A selective agonist is selective for a specific type of receptor. E.g.
An adrenergic agonist is a drug that stimulates a response from the adrenergic receptors. The five main categories of adrenergic receptors are: α 1 , α 2 , β 1 , β 2 , and β 3 , although there are more subtypes, and agonists vary in specificity between these receptors, and may be classified respectively.
Guanabenz (most selective agonist for alpha2-adrenergic as opposed to imidazoline-I1) Guanoxabenz (metabolite of guanabenz) Xylazine(not for human use), [5] Tizanidine; Methyldopa; Methylnorepinephrine; Norepinephrine [6] -3-nitrobiphenyline is an α 2C selective agonist as well as being a weak antagonist at the α 2A and α 2B subtypes. [7] [8 ...
Since ergot-dopamine agonist have antihypertensive qualities it is wise to monitor blood pressure when using dopamine agonists with antihypertensive drugs to ensure that the patient does not get hypotension. That includes the drug sildenafil which is commonly used to treat erectile dysfunction but also used for pulmonary hypertension. [21]
Partial agonists, like the anti-diarrhea drug loperamide and antagonists, like naloxegol for opioid-induced constipation, do not cross the blood–brain barrier, but can displace other opioids from binding to those receptors in the myenteric plexus. Because opioids are addictive and may result in fatal overdose, most are controlled substances.
In the laboratories that study drug addiction, researchers have found that the brain becomes conditioned by the repeated dopamine rush caused by heroin. “The brain is not designed to handle it,” said Dr. Ruben Baler, a scientist with the National Institute on Drug Abuse. “It’s an engineering problem.”
Other drugs act by binding to a receptor and mimicking the normal neurotransmitter. Such drugs are called receptor agonists. An example of a receptor agonist is morphine, an opiate that mimics effects of the endogenous neurotransmitter β-endorphin to relieve pain. Other drugs interfere with the deactivation of a neurotransmitter after it has ...