Agonists: full, partial, inverse and biased
Explains drugs that activate receptors: how much they can activate them (full vs partial), drugs that push activity below baseline (inverse), and drugs that activate only some of a receptor's signals (biased).
Where this fitsConnects to 3 · Unlocks 2
- Connects to
- How drugs bind: affinity, shape and binding site — Agonism is one of the two things binding can do: mimic.
- Receptor types: autoreceptors, heteroreceptors and location — Agonists at autoreceptors can turn a synapse down instead of up.
- Fast doors and slow keypads: ionotropic and metabotropic receptors — Biased agonism only applies to metabotropic (G protein-coupled) receptors.
- Unlocks
- Dose-response curves: potency, efficacy, slope and variability — Full vs partial agonists are two different efficacies on a dose-response curve.
- Treating addiction: substitution, antagonists, glutamate, vaccines — and the model's limits — Methadone (full) and buprenorphine (partial) treat opioid addiction for exactly these reasons.
Orient
Agonist – drug binds to receptor and acts similarly to (mimics) endogenous neurotransmitter. Agonists can be full, partial, or inverse. Endogenous neurotransmitters can be thought of as “balanced” agonists; some drugs can be “biased” agonists – selectively altering a certain signaling pathway of a metabotropic receptor (functional selectivity).
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.
- Agonist
“Drug binds to receptor and acts similarly to (mimics) endogenous neurotransmitter”Slides 05, p. 9
Examples: opioid drugs (μ-opioid agonism), classical psychedelics (5-HT2A agonism).
- Full / partial / inverse agonist
“Can be full, partial, or inverse”Slides 05, p. 9
Full reaches maximum, partial reaches only part of it, inverse pushes activity below baseline.
- Partial agonist
“Buprenorphine is partial agonist – use in treatment”Slides 05, p. 9
Aripiprazole partially agonizes D2; ropinirole fully agonizes D2.
- Balanced agonist
“Endogenous neurotransmitters can be thought of as “balanced” agonists”Slides 05, p. 12
Normal activation of all the receptor's signaling pathways.
- Biased agonist
“Some drugs can be “biased” agonists – selectively altering a certain signaling pathway of a metabotropic receptor”Slides 05, p. 12
Also called functional selectivity (Rankovic et al., 2016).
From your course: Course slides 05, pp. 9–12, 15
Tip: the ← and → keys move through the lesson.
Full lesson: Reversible receptor binding