Antagonists and allosteric modulators (PAMs and NAMs)
Explains drugs that block receptors (competitively or not) and drugs that tune a receptor from a second site, making the neurotransmitter work better (PAM) or worse (NAM).
Where this fitsConnects to 2 · Unlocks 2
- Connects to
- How drugs bind: affinity, shape and binding site — Orthosteric vs allosteric binding is what separates competitive from noncompetitive.
- Glutamate and GABA: the brain's accelerator and brake — Benzodiazepines are PAMs at the GABA-A receptor you met earlier.
- Unlocks
- Dose-response curves: potency, efficacy, slope and variability — Competitive antagonists shift the curve right; noncompetitive ones pull its ceiling down.
- Treating addiction: substitution, antagonists, glutamate, vaccines — and the model's limits — Naloxone and other antagonists are addiction and overdose treatments.
Orient
Antagonist – drug binds to and blocks receptor preventing endogenous neurotransmitter (and agonist drugs!) from binding entirely or activating fully; it does not itself change transmission, just blocks. Competitive antagonists block the same site as endogenous neurotransmitter; noncompetitive antagonists reduce activity due to binding at an allosteric site. Modulators: a positive allosteric modulator (PAM) increases and a negative allosteric modulator (NAM) decreases receptor affinity for NT.
Course terms
Your professor's wording, word for word from the slides. Learn the term and this definition — the explanation underneath is only there to help it make sense.
- Antagonist
“Does not itself change transmission, just blocks”Slides 05, p. 13
Examples: Thorazine (D2), naloxone (μ-opioid).
- Competitive antagonist
“Competitive (blocks same site as endogenous neurotransmitter, preventing binding)”Slides 05, p. 13
Can be overcome by more agonist; naloxone is competitive and reversible.
- Noncompetitive antagonist
“noncompetitive (reduces activity due to binding at allosteric site)”Slides 05, p. 13
Can't be overcome by more agonist.
- Positive allosteric modulator (PAM)
“Allosteric agonism; increases receptor affinity for NT”Slides 05, p. 16
Benzodiazepines – PAM at GABA-A.
- Negative allosteric modulator (NAM)
“Allosteric antagonism; decreases receptor affinity for NT”Slides 05, p. 16
Cannabidiol (CBD) – NAM at CB1.
From your course: Course slides 05, pp. 13–17, 39
Tip: the ← and → keys move through the lesson.
Full lesson: Reversible receptor binding