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.
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- Locks and keys: receptor specificity, agonists and antagonists — Picks up right after the key turns.
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- 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.
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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.
Términos del curso
Las palabras de tu profesor, tal cual aparecen en las diapositivas. Aprende el término y esta definición; la explicación de abajo solo ayuda a entenderla.
- Ionotropic receptor
“When activated, ion flow occurs immediately leading to depolarization or hyperpolarization”Diapositivas 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)”Diapositivas 03, p. 9
Ligand = whatever binds the receptor.
- Receptor subunits
“Smaller building blocks of ionotropic receptors”Diapositivas 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”Diapositivas 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”Diapositivas 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”Diapositivas 03, p. 12
Metabotropic activation can change functioning beyond EPSP/IPSP, even gene expression (CREB).
- Trk receptors
“Also metabotropic; no G-protein coupling”Diapositivas 03, p. 15
Trk = tyrosine/tropomyosin receptor kinase, pronounced “track”: TrkA, TrkB, TrkC.
- Neurotrophins
“Molecules that promote neuronal survival and growth”Diapositivas 03, p. 15
The big one for us is BDNF (brain-derived neurotrophic factor), which binds to TrkB.
De tu curso: Course slides 03, pp. 9–15
Consejo: las teclas ← y → recorren la lección.
Lección completa: Receptor signaling mechanisms