ionotropic receptors Flashcards
What are the main differences between ionotropic and metabotropic receptors?
Ionotropic receptors contain a ligand binding site and ion channel, while metabotropic receptors do not have ion channels and affect nearby ion channels via second messengers, most commonly via G-proteins.
What is the time frame for postsynaptic effects mediated by ionotropic receptors?
1-2 ms post action potential, short lasting (<1 ms)
Name some ligands that bind to ionotropic receptors.
- Ach
- Glutamate
- GABA
- Serotonin
- Glycine
- Drugs: nicotine (nAChRs), muscarine (mAChRs)
What are the three superfamilies of ionotropic receptors?
- Cys-loop receptors
- Ionotropic glutamate receptors
- ATP-gated receptors
What is the structure of Cys-loop receptors?
Pentameric, typically alpha-alpha-beta-gamma-delta with 4 transmembrane domains and 2 ligand binding sites.
How are AMPA receptors structured?
Tetrameric with 4 transmembrane domains each and 4 agonist binding sites.
What is the structure of P2X receptors?
Trimeric with 2 transmembrane domains each and 3 ligand binding sites.
How many genes encode the nicotinic acetylcholine receptor?
16
What is the role of alternative splicing in AMPA receptor subunits?
Generates diversity by producing flip and flop isoforms, affecting receptor recovery from desensitization.
What are the implications of RNA editing in GluA2 subunits?
Alters calcium permeability; unedited (Q) allows Ca²⁺ permeability, edited (R) is impermeable to Ca²⁺, protecting neurons from excitotoxicity.
True or False: The majority of GluA2 subunits are edited in healthy neurons.
True
What happens when ACh binds to the nicotinic ACh receptor?
Induces conformational changes, exposing (opening) the ion pore.
Fill in the blank: Nicotinic ACh receptors are widely expressed in the _______ and _______.
[muscular system], [nervous system]
What is the physiological role of nicotinic ACh receptors?
Mediate fast, excitatory synaptic transmission.
What is desensitization of nicotinic ACh receptors?
An accumulation of receptors in an agonist-bound but non-conducting conformational state.
What are the properties of AMPA receptors?
Permeable to Na+ and K+, generating excitatory postsynaptic potentials (EPSPs).
What does the activation of NMDA receptors require?
Binding of glutamate and glycine, plus membrane depolarization to remove Mg²⁺ block.
What is long-term potentiation (LTP)?
A cellular correlate of memory formation involving long-lasting enhancement in synapse transmission between two neurons.
What is the role of calcium influx in LTP?
Activates protein kinases leading to the insertion of additional AMPA receptors into the membrane.
What is long-term depression (LTD)?
A long decrease of synaptic function, typically induced by prolonged low-frequency synaptic stimulation.
What pathological condition is associated with mutations in nicotinic ACh receptor subunits?
Autosomal dominant frontal lobe epilepsy.
What is the effect of cigarette smoking on nicotinic ACh receptors?
Acts as an antidepressant through rapid AChR desensitization.
What is the significance of the R/G site in AMPA receptors?
Involves replacement of an arginine (R) with a glycine (G) through RNA editing, affecting recovery from desensitization.
