Fast doors and slow keypads: ionotropic and metabotropic receptors
Explains what happens after a receptor is activated — an instant ion flow, or a slower chain that can change the cell for a long time.
Where this fitsConnects to 1 · Unlocks 3
- Connects to
- Locks and keys: receptor specificity, agonists and antagonists — Picks up right after the key turns.
- Unlocks
- Dopamine: receptor families, clearance and pathways — All dopamine receptors are metabotropic.
- Glutamate and GABA: the brain's accelerator and brake — NMDA, AMPA and GABA-A are ionotropic.
- Acetylcholine: nicotinic, muscarinic and AChE — Nicotinic is ionotropic; muscarinic is metabotropic.
Orient
Ionotropic receptors – when activated, ion flow occurs immediately leading to depolarization or hyperpolarization; “ligand-gated”, fast acting, and made of subunits. Metabotropic receptors – G protein-coupled receptors (GPCR); slower acting. The G protein can open an ion channel from inside the neuron or lead to second messenger formation, and neuromodulation – long-term changes.
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.
- Ionotropic receptor
“When activated, ion flow occurs immediately leading to depolarization or hyperpolarization”Slides 03, p. 9
Fast acting; the receptor itself is the ion channel (the professor's “door with lock in it”).
- Ligand-gated
““Ligand-gated” as they become active when a ligand binds to them (e.g, neurotransmitters or drugs)”Slides 03, p. 9
Ligand = whatever binds the receptor.
- Receptor subunits
“Smaller building blocks of ionotropic receptors”Slides 03, p. 10
Receptors are discriminated by subunit composition, which changes how they respond to a neurotransmitter or drug.
- Metabotropic receptor (GPCR)
“G protein-coupled receptors; GPCR”Slides 03, p. 11
Slower acting; when activated the G protein decouples from the receptor (the “Wi-Fi keypad”).
- Second messenger
“G protein activates effector enzymes (e.g., adenylyl cyclase), producing second messenger”Slides 03, p. 12
The “first” messenger is the NT that binds to the receptor; e.g., cAMP is a second messenger.
- Neuromodulation
“Neuromodulation – long-term changes”Slides 03, p. 12
Metabotropic activation can change functioning beyond EPSP/IPSP, even gene expression (CREB).
- Trk receptors
“Also metabotropic; no G-protein coupling”Slides 03, p. 15
Trk = tyrosine/tropomyosin receptor kinase, pronounced “track”: TrkA, TrkB, TrkC.
- Neurotrophins
“Molecules that promote neuronal survival and growth”Slides 03, p. 15
The big one for us is BDNF (brain-derived neurotrophic factor), which binds to TrkB.
From your course: Course slides 03, pp. 9–15
Tip: the ← and → keys move through the lesson.
Full lesson: Receptor signaling mechanisms